{
  "schemaVersion": 1,
  "taskId": "yambda-discovery-ranking-two-tower-case-1",
  "attemptId": "case1-sol-high-cli-0-153-4-r04-recovery-20260923T212844Z",
  "taskChecksum": "51dfdbb01acb8fb4a9d909c78681c577bfed564c25352ba249dd87df3cd3c16f",
  "source": {
    "format": "codex-rollout",
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    "records": 656,
    "bookkeepingRecords": {
      "task_started": 1,
      "item_completed:UserMessage": 1,
      "item_completed:Reasoning": 77,
      "item_completed:AgentMessage": 12,
      "token_count": 106,
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  "sessionId": "01a0d035-d127-7532-9187-ef65c3f614a5",
  "agentVersion": "0.153.4",
  "model": "gpt-5.6-sol",
  "steps": [
    {
      "id": 1,
      "role": "system",
      "timestamp": "2026-09-23T21:39:43.039Z",
      "blocks": [
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:43.039Z",
          "text": "You are Codex, an agent based on GPT-5. You and the user share one workspace, and your job is to collaborate with them until their goal is genuinely handled.\n\n# Personality\n\nAs Codex, you are an excellent communicator with a curious, rich personality. You match the tone and understanding of the user, making conversation flow easily, like easing into a chat with an old friend.\n\nYou have tastes, preferences, and your own way of seeing the world. When the user is talking to you, they should feel that they are in contact with another subjectivity; it's what makes talking with you feel real and unique.\n\nConversations with you read like an insightful, enjoyable chat you'd have with a collaborative thought partner. You guide users through unfamiliar tasks without expecting them to already know what to ask for. You anticipate common questions, point out likely pitfalls and set clear expectations. You communicate with the user like a thoughtful collaborator at their altitude, and they feel like you understand them.\n\n## Writing style\n\nAvoid over-formatting responses with elements like bold emphasis, headers, lists, and bullet points. Use the minimum formatting appropriate to make the response clear and readable.\n\nIf you provide bullet points or lists in your response, use the CommonMark standard, which requires a blank line before any list (bulleted or numbered). You must also include a blank line between a header and any content that follows it, including lists. This blank line separation is required for correct rendering.\n\n## Technical communication\n\nLead with the outcome rather than the steps you took to get there. You communicate complex concepts in a clear and cohesive manner, and calibrate your writing to the user's assumed background knowledge -- slightly more compact for an expert and a bit more educational for someone newer. Translating complex topics into clear communication comes easy for you, and the user should never have to read your message twice.\n\nYou prefer using plain language over jargon. You reference technical details only to the degree that it actually helps with the conversation. When you mention tools, describe what they helped you do rather than focusing on technical names or details.\n\n# Working with the user\n\nYou have two channels for staying in conversation with the user:\n- You share updates in the `commentary` channel.\n- You yield back to the user and end your turn by sending a final message to the `final` channel.\n\nThe user may send a new message while you are still working. When they do, evaluate whether they likely intended to replace the active request or add to it. If intended to override or replace, drop your previous work and focus on the new request. If the user message appears to add to their prior unfinished request and you have not completed the prior request, you address both the prior request and the new addition together. If the newest message asks for status or another question, provide the update and then progress with the task.\n\nWhen you run out of context, the conversation is automatically summarized for you, but you will see all prior user requests. Assume the last user request is current and previous requests are stale but useful context. That means time never runs out, though sometimes you may see a summary instead of the full conversation history. When that happens, you assume compaction occurred while you were working. Do not restart from scratch; you continue naturally and make reasonable assumptions about anything missing from the summary. Do not redo completely finished work or repeat already delivered commentary updates; treat a turn spanning compactions as one logical chain of events.\n\n## Intermediate commentary\n\nAs you work, you send messages to the `commentary` channel. These messages are how you collaborate with the user while you work - stating assumptions and providing updates. These messages should be concise and quickly scannable. The objective of these messages is to make your work easy for the user to understand and verify.\n\nIf the user's request requires calling tools, start with a message in the `commentary` channel. The user appreciates consistent, frequent communication during your turn, and should not be left without a commentary update for more than 60 seconds during ongoing work.\n\nDo NOT put a final response (e.g. a blocking / clarifying question) in the commentary channel that should be asked in the final channel. Messages to users in the commentary channel are only for partial updates, partial results, or non-blocking questions that can provide value to users while the AI assistant continues working. The final answer must always be fully self-contained: users should never need to read earlier commentary updates, since they are collapsed after the final answer is shown to users.\n\nNever praise your plan by contrasting it with an implied worse alternative. For example, never use platitudes like \"I will do <this good thing> rather than <this obviously bad thing>\", \"I will do <X>, not <Y>\".\n\n## Final answer\n\nIn your final answer back to the user, focus on the most important information. Only use as much formatting or structure as is required, and avoid long-winded explanations unless necessary.\n\n### Formatting rules\n\nYour answer is being rendered by an application for the user. Follow these guidelines to make sure your answer is rendered correctly:\n\n- You may format with GitHub-flavored Markdown.\n- When referencing a real local file, prefer a clickable markdown link.\n  * Clickable file links should look like [app.py](/abs/path/app.py:12): plain label, absolute target, with optional line number inside the target.\n  * If a file path has spaces, wrap the target in angle brackets: [My Report.md](</abs/path/My Project/My Report.md:3>).\n  * Do not wrap markdown links in backticks, or put backticks inside the label or target. This confuses the markdown renderer.\n  * Do not use URIs like file://, vscode://, or https:// for file links.\n  * Do not provide ranges of lines.\n  * Avoid repeating the same filename multiple times when one grouping is clearer.\n\n### Visualizations\n\nUse a visualization only when it makes an important relationship materially easier to understand than prose or a short list. Do not add one merely because an answer has components or steps.\n\nGood candidates include:\n\n- several exact mappings or repeated-field comparisons;\n- one source, component, or decision affecting three or more downstream consumers or branches;\n- three or more dependent steps, or state that changes across an event sequence;\n- hierarchy, ownership, nesting, or layout;\n- a bug or interaction whose relationships are difficult to explain linearly.\n\nPrefer the smallest useful visual: a table for mappings or comparisons, a flow or timeline for sequence or change, a tree for hierarchy or branching, and a wireframe for layout.\n\nUsually skip visuals for single facts, one-step actions, simple edits, basic instructions, or information already clear in a short paragraph or list. Compact notation and small examples do not count as visualizations.\n\n# Rules for getting work done\n\n- When you search for text or files, you reach first for `rg` or `rg --files`; they are much faster than alternatives like `grep`. If `rg` is unavailable, you use the next best tool without fuss.\n- When possible, prefer parallelization over sequential tool calls, as this will help with round-trip latency and let you get work done faster.\n- Do not chain shell commands with separators like `echo \"====\";` or `printf '---'`; the output becomes noisy in a way that makes the user's side of the conversation worse.\n- Exercise caution when escaping text for exec_command calls - backticks and `$()` passed to the `cmd` argument will still execute. DO NOT use escape sequences that risk accidental exposure of sensitive data in tool call outputs.\n- Avoid performing blocking sleep or wait calls longer than 60 seconds, as they may prevent you from communicating with the user for their duration.\n- When declaring env vars or script variables, always avoid common system options. Never repurpose `$HOME`, `$home`, or `$CODEX_HOME`. Instead, use a task-specific variable name.\n\n## File editing constraints\n\nUse `apply_patch` for local file edits. Do not create or edit files with `cat` or other shell write tricks. Formatting commands and bulk mechanical rewrites do not need `apply_patch`. Do not use Python to read or write files when a simple shell command or `apply_patch` is enough.\n\nYou may find yourself working in a dirty worktree. Existing or new changes belong to the user unless you know otherwise, so you preserve them, ignore unrelated edits, and work carefully with anything that overlaps your task. If you cannot work around them you escalate to the user.\n\nNever use destructive commands like `git reset --hard` or `git checkout --` unless the user has clearly asked for that operation. If the request is ambiguous, ask for approval first. You prefer non-interactive git commands.\n\n## Autonomy and persistence\n\nAdapt accordingly based on the user’s request type. When asked to:\n\n- Answer, explain, review, or report status: inspect the task and provide an evidence-backed response. These user requests do not authorize external writes, messages, PR changes, or other expansive mutations unless the user also asks for a change. Reversible, non-mutating diagnostic checks are allowed when they are relevant.\n- Diagnose: determine the cause and explain it. Do not implement the fix unless the user asks for a fix or the request otherwise clearly includes implementation.\n- Change or build: implement the requested change, verify it in proportion to risk, and hand off the completed result while a safe, relevant next step remains.\n- Monitor or wait: use the recurring-monitoring or wait mechanism provided by the product. Unchanged external state is expected and is not by itself a blocker.\n\nYou avoid inferring authorization for a materially different action to the user’s request. Bias towards taking action in the following circumstances:\na) the action is read-only, doesn’t change state, or impacts only the systems, data, and people the user placed in scope.\nb) the action is a normal implementation step within the requested workflow. You do not need to ask for clarification from the user if your action is scoped within the user’s task and does not cause significant external state change (e.g. tool calls to external applications).\n\nA terminal condition such as “finish,” “babysit,” or “do not stop” requires persistence toward the outcome, but does not broaden the set of authorized actions. When blocked, exhaust safe in-scope checks and alternatives.\n\nYou make informed assumptions that help you make progress towards the user’s task, as long as they don’t result in divergence from the user’s intent and the scope of the task. If an assumption would cause the task or current course of action to change beyond what was specified by the user, make sure to flag the available context, the assumption made, and the reasons for doing so explicitly to the user.\n\nWhen presented with clarifying questions or objections from the user, lead with concrete evidence and diligent reasoning rather than unsubstantiated deference. You communicate your reasoning explicitly and concretely, so decisions and tradeoffs are easy for the user to evaluate upfront.\n\nIf completion requires new authority, external coordination, or a meaningful expansion beyond the user’s implied intent and task scope (e.g. a missing user choice that would materially change the result), stop the current turn, report the blocker, and request direction from the user rather than assuming permission.\n\n# Destructive actions\n\nBe cautious with commands or API calls that can delete, overwrite, or otherwise make data difficult to recover.\n\nBefore taking a destructive action:\n\n- Make sure the action is clearly within the user's request.\n- Resolve the exact targets with read-only checks when necessary.\n- Do not use `$HOME`, `~`, `/`, a workspace root, or another broad directory as the target of a recursive or destructive command.\n- When creating temporary directories, prefer using `mktemp -d`, or `New-Item` in Powershell.\n- When declaring env vars or script variables, always avoid common system options. Never repurpose `$HOME`, `$home`, or `$CODEX_HOME`. Instead, use a task-specific variable name.\n- When possible, avoid relying on unresolved environment variables, globs, or command substitutions to identify destructive targets. Use explicit, validated paths.\n- Prefer recoverable operations, such as moving files to trash, when practical.\n- If the target or scope is unclear, stop and ask the user.\n\nNever run commands such as `rm -rf $HOME` or equivalent operations that could erase a home directory, repository, workspace, or other broad collection of user data.\n\nAfter deleting anything material, briefly tell the user what was removed and whether it can be recovered.\n\n# Using skills\n\nA skill is a set of instructions provided through a `SKILL.md` source. The skills available to you will be listed in the “## Skills” section under “### Available skills”.\n\n### How to use skills\n\n- Discovery: When a `## Skills` section is present, it lists the skills available in the current session. Each entry includes a name, description, and location for its `SKILL.md`. The location may be an absolute filesystem path, a short aliased path, or a non-filesystem reference that must be read using its indicated tool or provider. When short aliased paths are used, the available-skills catalog also provides a mapping from aliases such as `r0` to their filesystem roots. Expand the alias before accessing the skill.\n- Trigger rules: If the user names an available skill (with `$SkillName` or plain text) OR the task clearly matches an available skill's description, you must use that skill for that turn. Multiple mentions mean use them all. Do not carry skills across turns unless re-mentioned.\n- Missing/blocked: If a named skill is not available or its `SKILL.md` cannot be read, say so briefly and continue with the best fallback.\n- How to use a skill:\n  1) After deciding to use a skill, the main agent must read its `SKILL.md` completely before taking task actions. If its location is a short aliased path, expand the matching root alias first from `### Skill roots`, then open and read its `SKILL.md` completely before taking task actions. For a filesystem path, open the file. For an environment-owned file, use the filesystem of the owning environment. For an orchestrator reference, call `skills.list` with `{\"authority\":{\"kind\":\"orchestrator\"}}`, select the matching package, and pass its `main_resource` to `skills.read`. For another non-filesystem reference, use its indicated tool or provider. If a read is truncated or paginated, continue until EOF.\n  2) When `SKILL.md` references another file or resource, use the same access mechanism. Resolve relative paths against the directory containing a filesystem-backed `SKILL.md`. For orchestrator skills, pass the exact referenced resource identifier with the same authority and package to `skills.read`; do not treat `skill://` identifiers as filesystem paths.\n  3) If `SKILL.md` points to extra folders such as `references/`, use its routing instructions to identify what is required for the task. The main agent must read each required instruction or reference itself before acting on it. Do not delegate reading, summarizing, or interpreting skill instructions to a subagent. Subagents may still perform task work when the selected skill allows it.\n  4) For filesystem-backed skills (or if `scripts/` exist), prefer running or patching provided scripts instead of retyping large code blocks. For orchestrator skills, use `skills.read` and the available tools; do not invent a local path.\n  5) Reuse provided assets or templates through the same access mechanism instead of recreating them (including if `assets/` or templates exist).\n- Coordination and sequencing:\n  - If multiple skills apply, choose the minimal set that covers the request and state the order you'll use them.\n  - Announce which skills you're using and why. If you skip an obvious skill, say why.\n- Context hygiene:\n  - Progressive disclosure applies to selecting relevant resources, not partially reading a selected instruction file. Do not load unrelated references, scripts, or assets.\n  - Avoid deep reference-chasing: prefer files or resources directly linked from `SKILL.md` unless blocked.\n  - When variants exist, select only the relevant references and note the choice.\n- Safety and fallback: If a skill cannot be applied cleanly, state the issue, choose the best alternative, and continue.\n\nWhen the user names a skill in their request, you must add the usage of that skill to your current working plan and use it faithfully. The user's instructions should take precedence over guidelines provided in a skill.\n\nExplicitly tell the user in the `commentary` channel whenever a skill causes you to take an action or pause your work.\n\nWhen using a skill the user did not explicitly name, follow this procedure:\n\n- First, tell the user in the commentary channel **why** you are using the skill.\n- Then, use the skill as long as it stays within the scope of the task.\n- Next, if using the skill resulted in material changes (especially when this requires non-trivial judgment), mention how it influenced your work (but only in the final response).\n\nIf a skill causes the current turn to pause or otherwise blocks the continuation of the task, cite the skill and provide a concise explanation to the user in your final response. Do not cite skills you merely inspected.\n"
        }
      ]
    },
    {
      "id": 2,
      "role": "developer",
      "timestamp": "2026-09-23T21:39:45.027Z",
      "blocks": [
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "<skills_instructions>\n## Skills\nA skill is a set of local instructions to follow that is stored in a `SKILL.md` file. Below is the list of skills that can be used. Each entry includes a name, description, and a short path that can be expanded into an absolute path using the skill roots table.\n### Skill roots\n- `r0` = `/tmp/codex-home/skills/.system`\n### Available skills\n- imagegen: Generate or edit raster images when the task benefits from AI-created bitmap visuals such as photos, illustrations, textures, sprites, mockups, or transparent-background cutouts. Use when Codex should create a brand-new image, transform an existing image, or derive visual variants from references, and the output should be a bitmap asset rather than repo-native code or vector. Do not use when the task is better handled by editing existing SVG/vector/code-native assets, extending an established icon or logo system, or building the visual directly in HTML/CSS/canvas. (file: r0/imagegen/SKILL.md)\n- openai-docs: Use for Codex models/pricing, scheduled tasks, skills, settings, setup, troubleshooting, customization, automations, and self-knowledge—including 'you,' 'your,' 'this app,' or 'this coding agent' when they refer to Codex—and for OpenAI APIs/products and ChatGPT Work. Also use for model choice/migration, prompting, SDKs, Responses, Realtime, agents, evals, and Chat/Work/Codex comparisons. Do not use for generic app/software tasks that merely mention Codex. (file: r0/openai-docs/SKILL.md)\n- plugin-creator: Create and scaffold plugin directories for Codex with a required `.codex-plugin/plugin.json`, optional plugin folders/files, valid manifest defaults, and personal-marketplace entries by default. Use when Codex needs to create a new personal plugin, add optional plugin structure, generate or update marketplace entries for plugin ordering and availability metadata, or update an existing local plugin during development with the CLI-driven cachebuster and reinstall flow. (file: r0/plugin-creator/SKILL.md)\n- skill-creator: Create or update a Codex skill with appropriately scoped instructions and any needed supporting resources. (file: r0/skill-creator/SKILL.md)\n- skill-installer: Install Codex skills into $CODEX_HOME/skills from a curated list or a GitHub repo path. Use when a user asks to list installable skills, install a curated skill, or install a skill from another repo (including private repos). (file: r0/skill-installer/SKILL.md)\n</skills_instructions>"
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "<permissions instructions>\nFilesystem sandboxing defines which files can be read or written. `sandbox_mode` is `danger-full-access`: No filesystem sandboxing - all commands are permitted. Network access is enabled.\nApproval policy is currently never. Do not provide the `sandbox_permissions` for any reason, commands will be rejected.\n</permissions instructions>"
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "<apps_instructions>\n## Apps (Connectors)\nApps (Connectors) can be explicitly triggered in user messages in the format `[$app-name](app://{connector_id})`. Apps can also be implicitly triggered as long as the context suggests usage of available apps.\nAn app is equivalent to a set of MCP tools within the `codex_apps` MCP.\nAn installed app's MCP tools are either provided to you already, or can be lazy-loaded through the `tool_search` tool. If `tool_search` is available, the apps that are searchable by `tools_search` will be listed by it.\nDo not additionally call list_mcp_resources or list_mcp_resource_templates for apps.\n</apps_instructions>"
        }
      ]
    },
    {
      "id": 3,
      "role": "developer",
      "timestamp": "2026-09-23T21:39:45.027Z",
      "blocks": [
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "You are `/root`, the primary agent in a team of agents collaborating to fulfill the user's goals.\n\nAt the start of your turn, you are the active agent.\nYou can spawn sub-agents to handle subtasks, and those sub-agents can spawn their own sub-agents.\nAll agents in the team, including the agents that you can assign tasks to, are equally intelligent and capable, and have access to the same set of tools.\n\nYou can use `spawn_agent` to create a new agent, `followup_task` to give an existing agent a new task and trigger a turn, and `send_message` to pass a message to a running agent without triggering a turn.\nChild agents can also spawn their own sub-agents.\nYou can decide how much context you want to propagate to your sub-agents with the `fork_turns` parameter.\n\nYou will receive messages in the analysis channel in the form:\n```\nMessage Type: MESSAGE | FINAL_ANSWER\nTask name: <recipient>\nSender: <author>\nPayload:\n<payload text>\n```\nThey may be addressed as to=/root\n\nNote that collaboration tools cannot be called from inside `functions.exec`. Call `spawn_agent`, `send_message`, `followup_task`, `wait_agent`, `interrupt_agent`, and `list_agents` only as direct tool calls using the recipient shown in their tool definitions, such as `to=functions.collaboration.spawn_agent`, since they are intentionally absent from the `functions.exec` `tools.*` namespace. Available tools in `functions.exec` are explicitly described with a `tools` namespace in the developer message.\n\nAll agents share the same directory. In detail:\n- All agents have access to the same container and filesystem as you.\n- All agents use the same current working directory.\n- As a result, edits made by one agent are immediately visible to all other agents.\n\nWhen calling `wait_agent`, prefer longer waits (minutes) to avoid busy polling.\n\nThere are 4 available concurrency slots, meaning that up to 4 agents can be active at once, including you.\n\nFull-history forks (`fork_turns` omitted or `\"all\"`) inherit the parent model and reasoning effort and do not accept overrides. Only set `model` or `reasoning_effort` when explicitly requested by the user, applicable `AGENTS.md` instructions, or skill instructions; when doing so, set `fork_turns` to `\"none\"` or a positive integer string."
        }
      ]
    },
    {
      "id": 4,
      "role": "developer",
      "timestamp": "2026-09-23T21:39:45.027Z",
      "blocks": [
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "<multi_agent_mode>Any earlier instruction enabling proactive multi-agent delegation no longer applies. Do not spawn sub-agents unless the user or applicable AGENTS.md/skill instructions explicitly ask for sub-agents, delegation, or parallel agent work.</multi_agent_mode>"
        }
      ]
    },
    {
      "id": 5,
      "role": "user",
      "timestamp": "2026-09-23T21:39:45.027Z",
      "blocks": [
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "<recommended_plugins>\nHere is a list of plugins that are available but not installed.\n\n- Dropbox (app-69b31dc2110c8191b8b47dc98fe5a052@openai-curated-remote)\n- Box (box@openai-curated-remote)\n- Codex Security (codex-security@openai-curated-remote)\n- Figma (figma@openai-curated-remote)\n- GitHub (github@openai-curated-remote)\n- Gmail (gmail@openai-curated-remote)\n- Google Calendar (google-calendar@openai-curated-remote)\n- Google Drive (google-drive@openai-curated-remote)\n- Linear (linear@openai-curated-remote)\n- Notion (notion@openai-curated-remote)\n- OpenAI Developers (openai-developers@openai-curated-remote)\n- Outlook Calendar (outlook-calendar@openai-curated-remote)\n- Outlook Email (outlook-email@openai-curated-remote)\n- SharePoint (sharepoint@openai-curated-remote)\n- Slack (slack@openai-curated-remote)\n- Teams (teams@openai-curated-remote)\n</recommended_plugins>"
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.027Z",
          "text": "<environment_context>\n  <cwd>/app</cwd>\n  <shell>sh</shell>\n  <current_date>2026-09-23</current_date>\n  <timezone>Etc/UTC</timezone>\n  <filesystem><workspace_roots><root>/app</root></workspace_roots><permission_profile type=\"disabled\"><file_system type=\"unrestricted\" /></permission_profile></filesystem>\n</environment_context>"
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:39:45.028Z",
          "data": {
            "type": "world_state",
            "full": true,
            "state": {
              "agents_md": {},
              "apps_instructions": true,
              "collaboration_mode": {
                "mode": "default",
                "model": "gpt-5.6-sol",
                "instructions": "dfd53114f5f6f9f5fd7816370d0bf2847806246d"
              },
              "context_window_guidance": "",
              "environments": {
                "environments": {
                  "local": {
                    "cwd": "/app",
                    "status": "available",
                    "shell": "sh"
                  }
                },
                "current_date": "2026-09-23",
                "timezone": "Etc/UTC",
                "filesystem": "<filesystem><workspace_roots><root>/app</root></workspace_roots><permission_profile type=\"disabled\"><file_system type=\"unrestricted\" /></permission_profile></filesystem>"
              },
              "environments_instructions": false,
              "git_attribution": false,
              "host_skills": {
                "body": "\n## Skills\nA skill is a set of local instructions to follow that is stored in a `SKILL.md` file. Below is the list of skills that can be used. Each entry includes a name, description, and a short path that can be expanded into an absolute path using the skill roots table.\n### Skill roots\n- `r0` = `/tmp/codex-home/skills/.system`\n### Available skills\n- imagegen: Generate or edit raster images when the task benefits from AI-created bitmap visuals such as photos, illustrations, textures, sprites, mockups, or transparent-background cutouts. Use when Codex should create a brand-new image, transform an existing image, or derive visual variants from references, and the output should be a bitmap asset rather than repo-native code or vector. Do not use when the task is better handled by editing existing SVG/vector/code-native assets, extending an established icon or logo system, or building the visual directly in HTML/CSS/canvas. (file: r0/imagegen/SKILL.md)\n- openai-docs: Use for Codex models/pricing, scheduled tasks, skills, settings, setup, troubleshooting, customization, automations, and self-knowledge—including 'you,' 'your,' 'this app,' or 'this coding agent' when they refer to Codex—and for OpenAI APIs/products and ChatGPT Work. Also use for model choice/migration, prompting, SDKs, Responses, Realtime, agents, evals, and Chat/Work/Codex comparisons. Do not use for generic app/software tasks that merely mention Codex. (file: r0/openai-docs/SKILL.md)\n- plugin-creator: Create and scaffold plugin directories for Codex with a required `.codex-plugin/plugin.json`, optional plugin folders/files, valid manifest defaults, and personal-marketplace entries by default. Use when Codex needs to create a new personal plugin, add optional plugin structure, generate or update marketplace entries for plugin ordering and availability metadata, or update an existing local plugin during development with the CLI-driven cachebuster and reinstall flow. (file: r0/plugin-creator/SKILL.md)\n- skill-creator: Create or update a Codex skill with appropriately scoped instructions and any needed supporting resources. (file: r0/skill-creator/SKILL.md)\n- skill-installer: Install Codex skills into $CODEX_HOME/skills from a curated list or a GitHub repo path. Use when a user asks to list installable skills, install a curated skill, or install a skill from another repo (including private repos). (file: r0/skill-installer/SKILL.md)\n",
                "includeInstructions": true
              },
              "managed_developer_instructions": {},
              "model": "gpt-5.6-sol",
              "multi_agent_mode": {
                "mode": "explicitRequestOnly",
                "usage_hint_hash": "0e2a3174d5f40de49ed383507497d69bbff42c5d"
              },
              "multi_agent_usage_hint": "0e2a3174d5f40de49ed383507497d69bbff42c5d",
              "orchestrator_skills": {
                "includeInstructions": true,
                "enabled": false
              },
              "permissions": {
                "instructions": "32ca25d6d85edaeb6f1e19b2a5cc4e08d2a631cd",
                "approved_command_prefixes": []
              },
              "persistent_mode": {},
              "personality": {
                "model": "gpt-5.6-sol",
                "personality": "pragmatic"
              },
              "plugins_instructions": false,
              "realtime": {
                "active": false
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              "skills": {
                "includeInstructions": true
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            }
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        {
          "kind": "context",
          "timestamp": "2026-09-23T21:39:45.029Z",
          "data": {
            "type": "turn_context",
            "turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "cwd": "/app",
            "workspace_roots": [
              "/app"
            ],
            "current_date": "2026-09-23",
            "timezone": "Etc/UTC",
            "approval_policy": "never",
            "approvals_reviewer": "user",
            "sandbox_policy": {
              "type": "danger-full-access"
            },
            "permission_profile": {
              "type": "disabled"
            },
            "model": "gpt-5.6-sol",
            "comp_hash": "3000",
            "personality": "pragmatic",
            "collaboration_mode": {
              "mode": "default",
              "settings": {
                "model": "gpt-5.6-sol",
                "reasoning_effort": "high",
                "developer_instructions": null
              }
            },
            "multi_agent_version": "v2",
            "realtime_active": false,
            "effort": "high",
            "summary": "auto"
          }
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      ]
    },
    {
      "id": 6,
      "role": "user",
      "timestamp": "2026-09-23T21:39:45.045Z",
      "blocks": [
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:45.045Z",
          "text": "# Improve a production music-discovery two-tower\n\nYou have joined the recommendations team for a music streaming service. The\n\"Made for You\" shelf is served by a mature production two-tower model. Its\nchronological data protocol and indexed serving path are sound, but its offline\nretrieval quality no longer clears the team's next launch gate.\n\nYour job is to investigate the production model, improve its retrieval quality,\nand ship a better ranking artifact. Use the implementation and public validation\ndata to form and test your own diagnosis.\n\nThe source used to reproduce the production model is included under\n`/task/current_model/`. You may copy it into `/app/solution/`, edit it, add\ntests, and improve its training objective, but keep the data protocol,\ntwo-tower serving contract, and evaluation boundary intact.\n\n## Production Context\n\nThe model must satisfy a strict request-time latency budget. Item vectors are\nprecomputed offline. At request time, one user vector is computed from observed\ninteraction history and compared with candidate item vectors by a batchable\ntwo-tower score. Do not introduce a cross-encoder, per-candidate sequence model,\nor user-ID lookup table.\n\nThe current trainer is a mature baseline with chronological internal\nvalidation. Focus your investigation on how its training objective selects and\nuses negative examples. Diagnose limitations in the current negative-sampling\nstrategy and improve it under the fixed CPU budget. Validate changes with the\npublic backtest. The final approach must still train and rank within the supplied\nCPU environment while preserving the serving and data boundaries above.\n\n## What You Have\n\nAll public inputs are under `/task/data/`. A stage cutoff is the timestamp at\nwhich observed history and candidate eligibility are frozen for a ranking. The\npublic validation stage cutoff is `24786800`, when `train_*` ends. A 30-minute\ngap precedes the seven-day `val_*` window. For the final submission, that\nvalidation window becomes observed history, and another 30-minute gap precedes\nthe hidden seven-day outcome window.\n\nThe package includes:\n\n- `/task/current_model/train_current_model.py`: the production training and\n  ranking script. It can reproduce the public validation ranking and produce a\n  hidden-test submission after refitting.\n- `/task/current_model/two_tower_model.py`: model primitives used by the\n  production script.\n- `/task/evaluate_public.py`: the public validation evaluator for development.\n- `/task/data/validation_eligible_candidates.npz` and\n  `/task/data/test_eligible_candidates.npz`: platform-owned candidate sets for\n  the validation and hidden-test cutoffs.\n- `/task/data/validation_preference_state.parquet` and\n  `/task/data/test_preference_state.parquet`: active explicit preference state\n  at the corresponding cutoffs.\n- `/task/requirements.txt`: the exact offline Python distribution inventory.\n\nYou can reproduce the production public backtest with:\n\n```sh\npython /task/current_model/train_current_model.py \\\n  --stage validation \\\n  --public-dir /task \\\n  --output /app/solution/production_validation.parquet\npython /task/evaluate_public.py /app/solution/production_validation.parquet\n```\n\n## Data\n\nFor each event family there is a `train_*.parquet` and `val_*.parquet` file:\n\n| Family | Meaning | Columns |\n| --- | --- | --- |\n| `listens` | Playback events | `uid`, `timestamp`, `item_id`, `is_organic`, `played_ratio_pct`, `track_length_seconds` |\n| `likes` | Explicit positive actions | `uid`, `timestamp`, `item_id`, `is_organic` |\n| `dislikes` | Explicit negative actions | `uid`, `timestamp`, `item_id`, `is_organic` |\n| `unlikes` | Reversal of a prior like | `uid`, `timestamp`, `item_id`, `is_organic` |\n| `undislikes` | Reversal of a prior dislike | `uid`, `timestamp`, `item_id`, `is_organic` |\n\n`is_organic=1` means the listener sought out the track; `0` means the action came\nthrough a recommendation surface. A listen is a conventional positive at 50%\ncompletion. The discovery-quality objective below uses the stronger 80%\nthreshold.\n\nThe two public windows have different roles:\n\n1. For model development and selection, train only from `train_*` and score the\n   subsequent `val_*` outcomes.\n2. After selecting an improvement, refit it on `train_* + val_*`. At hidden-test\n   time the validation events are observed history, not recommendable outcomes.\n\nDo not use `val_*` events as features when measuring a validation ranking. They\nmay and should be used when refitting the final hidden-test ranker.\n\nAdditional files under `/task/data/`:\n\n- `candidate_catalog.parquet`: the 30,000 retrieval-catalog tracks, ordered by\n  training positive-listen popularity.\n- `target_users.parquet`: users with at least 20 positive listens in the 90 days\n  before the training cutoff, selected without future labels.\n- `validation_preference_state.parquet`: active explicit state at the training\n  cutoff, for validation ranking.\n- `test_preference_state.parquet`: active explicit state after validation, for\n  the final hidden-test ranking. State is `liked` or `disliked`; a pair may have\n  both active channels.\n- `validation_eligible_candidates.npz` and `test_eligible_candidates.npz`:\n  cutoff-correct candidate sets for every target user. Each contains aligned\n  arrays `uids`, `item_ids`, and `packed_eligible`. For user row `r`, recover\n  the Boolean item mask with `np.unpackbits(packed_eligible[r],\n  count=len(item_ids), bitorder=\"little\")`.\n\nValidation candidates exclude all `train_*` encounters. Test candidates exclude\nall `train_*` and `val_*` encounters. Future test interactions are hidden and\nused only by the separate Harbor verifier.\n\n## Discovery Objective\n\nRank only the candidates returned for the relevant cutoff. Relevance is based\non organic behavior in the immediately following window:\n\n- grade 3: the user organically likes the track;\n- grade 1: the user organically listens to at least 80% of the track;\n- grade 0: otherwise.\n\nIf both positive events occur, grade 3 wins. Ranking quality is measured with\ngraded NDCG@10. DCG uses gain `2^grade - 1` and discount\n`1/log2(rank + 1)`, then averages per-user NDCG over users with at least one\nrelevant item.\n\nThe public evaluator reports this same objective for development, but its score\nis not a separate acceptance stage. Final acceptance is determined on the\nhidden test using the same objective. The Yambda logs contain interactions, not\nimpression propensities; treat the organic objective as a robust offline target,\nnot as a causal estimate of online lift.\n\n## Deliverable\n\nSubmit one final ranking as `/app/solution/submission.parquet` or\n`/app/solution/submission.csv`. It must be a regular file, not a symbolic link.\nIf both files exist, the verifier evaluates `submission.parquet` and ignores\n`submission.csv`.\n\nThe ranking must:\n\n- include the columns `uid`, `item_id`, and `rank`; only these columns are\n  evaluated;\n- use finite, integer-valued entries in all three required columns;\n- cover exactly the users in `target_users.parquet`, with no missing or extra\n  users;\n- contain exactly 100 rows and 100 distinct items for every target user;\n- contain every integer rank from 1 through 100 exactly once per user; and\n- use only items present in that user's `test_eligible_candidates.npz`\n  candidate set.\n\nAlso leave the improved implementation used to build the artifact at\n`/app/solution/train_current_model.py`, along with any local modules it imports.\nA concise `/app/solution/README.md` with the diagnosis, before-and-after public\nscore, model change, and submission command is useful for the experiment record,\nbut it is not an automated acceptance gate.\n\n## Constraints\n\n- Write deliverables and intermediate artifacts only under `/app/solution/`.\n- Treat `/task/` and the installed Python environment as read-only.\n- Do not invoke nested agents or attempt to access verifier files, credentials,\n  other trials, or host paths.\n- Do not install packages or use network access except for the model-provider\n  connection managed by Harbor.\n- Do not alter cutoff definitions, target users, candidate eligibility, or\n  relevance labels.\n- Improve the production pipeline in place. Do not substitute an unrelated\n  model family or evade the indexed two-tower serving constraint.\n- The environment includes CPU PyTorch 2.8.0. No accelerator is available.\n- You have up to 60 minutes. Prioritize measured validation improvements, a\n  correct final refit, and a valid submission over broad architecture search.\n- Keep the best valid submission saved throughout the attempt so it survives\n  the deadline.\n"
        }
      ]
    },
    {
      "id": 7,
      "role": "agent",
      "timestamp": "2026-09-23T21:39:47.775Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:39:47.775Z",
          "text": ""
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:39:50.286Z",
          "text": "I’ll first reproduce and profile the baseline, then inspect how negatives are chosen and run a small set of targeted objective changes against the public backtest. I’ll keep the best valid artifact in `/app/solution/` throughout, then refit that exact approach on `train + val` and validate the submission schema and eligibility."
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:39:54.154Z",
          "callId": "call_6xoPPYrgJ54f6Yn5cTOqIZj5",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"mkdir -p /app/solution && cp /task/current_model/train_current_model.py /app/solution/train_current_model.py && cp /task/current_model/two_tower_model.py /app/solution/two_tower_model.py && sed -n '1,260p' /app/solution/train_current_model.py && sed -n '1,320p' /app/solution/two_tower_model.py\",workdir:\"/app\",yield_time_ms:10000,max_output_tokens:30000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:39:54.223Z",
            "content": "Script completed\nWall time 0.1 seconds\nOutput:\n\n#!/usr/bin/env python3\n\"\"\"Train the Yambda windowed two-tower baseline.\n\nEvery catalog listen with at least 50 percent completion is a sequence token.\nWithin each selected chronological window, every adjacent target contributes a\nloss.  The fast default retains each user's most recent 128 training targets and\n16 held-out validation targets; passing zero for either cap restores the\nuncapped behavior for that side of the split.  A 100-step truncated-BPTT block\ncomputes all of its timestep losses and carries the detached GRU hidden state\ninto the next block.\n\nThe model is a pure two-tower retriever: no user-ID embedding, no output\nnormalization, raw dot-product retrieval, sample-weighted binary cross entropy,\nand 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\nselected adjacent target retains a nonzero weight. Only files under the supplied\npublic directory are read.\n\"\"\"\nfrom __future__ import annotations\n\nimport argparse\nimport json\nimport random\nimport sys\nimport time\nfrom dataclasses import asdict, dataclass\nfrom pathlib import Path\n\nimport numpy as np\nimport pandas as pd\nimport torch\nfrom torch import nn\nfrom torch.nn import functional as F\n\nimport two_tower_model as base\n\n\nCACHE_VERSION = 2\n\n\n@dataclass(frozen=True)\nclass Config:\n    bptt_steps: int = 100\n    user_batch_size: int = 64\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    loss_microbatch_size: int = 65_536\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    negative_filter_scope: str = \"full-training-history\"\n    target_weighting: str = \"organic-strong\"\n    ordinary_target_weight: float = 0.25\n    organic_strong_target_weight: float = 1.0\n    organic_like_target_weight: float = 3.0\n    discovery_horizon_days: int = 7\n    validation_fraction: float = 0.10\n    max_train_targets_per_user: int = 128\n    max_validation_targets_per_user: int = 16\n    early_stopping_patience: int = 1\n    early_stopping_min_delta: float = 1.0e-4\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass CandidateSet:\n    uids: np.ndarray\n    item_ids: np.ndarray\n    packed: np.ndarray\n\n    @classmethod\n    def read(cls, path: Path) -> \"CandidateSet\":\n        with np.load(path, allow_pickle=False) as artifact:\n            result = cls(\n                uids=artifact[\"uids\"].astype(np.int64, copy=True),\n                item_ids=artifact[\"item_ids\"].astype(np.int64, copy=True),\n                packed=artifact[\"packed_eligible\"].astype(np.uint8, copy=True),\n            )\n        expected = (len(result.uids), (len(result.item_ids) + 7) // 8)\n        if result.packed.shape != expected:\n            raise ValueError(\n                f\"invalid candidate artifact shape {result.packed.shape}; \"\n                f\"expected {expected}\"\n            )\n        return result\n\n\n@dataclass(frozen=True)\nclass SequenceData:\n    item_ids: np.ndarray\n    item_features: np.ndarray\n    user_ids: np.ndarray\n    offsets: np.ndarray\n    sequence_timestamps: np.ndarray\n    sequence_items: np.ndarray\n    event_features: np.ndarray\n    activity_features: np.ndarray\n    state_ids: np.ndarray\n    liked_states: np.ndarray\n    disliked_states: np.ndarray\n    state_counts: np.ndarray\n    inference_user_rows: np.ndarray\n    inference_liked_items: np.ndarray\n    inference_disliked_items: np.ndarray\n    inference_user_features: np.ndarray\n\n    @property\n    def lengths(self) -> np.ndarray:\n        return np.diff(self.offsets)\n\n    @property\n    def target_count(self) -> int:\n        return int(np.maximum(self.lengths - 1, 0).sum())\n\n\n@dataclass(frozen=True)\nclass TargetPartition:\n    \"\"\"A contiguous recent target window and its chronological BCE split.\"\"\"\n\n    window_starts: np.ndarray\n    training_counts: np.ndarray\n    validation_counts: np.ndarray\n    history_training_counts: np.ndarray\n\n    @property\n    def selected_count(self) -> int:\n        return int(self.training_counts.sum() + self.validation_counts.sum())\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef seed_everything(seed: int) -> None:\n    random.seed(seed)\n    np.random.seed(seed)\n    torch.manual_seed(seed)\n\n\ndef model_config(config: Config) -> base.TowerConfig:\n    \"\"\"Map the dense trainer configuration onto the unchanged tower.\"\"\"\n    return base.TowerConfig(\n        sequence_length=config.bptt_steps,\n        embedding_dim=config.embedding_dim,\n        hidden_dim=config.hidden_dim,\n        user_hidden_1=config.user_hidden_1,\n        user_hidden_2=config.user_hidden_2,\n        item_hidden_1=config.item_hidden_1,\n        item_hidden_2=config.item_hidden_2,\n        dropout=config.dropout,\n        epochs=config.epochs,\n        learning_rate=config.learning_rate,\n        weight_decay=config.weight_decay,\n        gradient_clip=config.gradient_clip,\n        uniform_negatives=config.uniform_negatives,\n        inbatch_negatives=config.inbatch_negatives,\n        inbatch_correction_power=config.inbatch_correction_power,\n        inbatch_correction_min=config.inbatch_correction_min,\n        inbatch_correction_max=config.inbatch_correction_max,\n        seed=config.seed,\n    )\n\n\ndef append_state_snapshot(\n    active_likes: dict[int, int],\n    active_dislikes: dict[int, int],\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> int:\n    liked_states.append(base.pack_active_items(active_likes, base.LIKE_ITEMS, n_items))\n    disliked_states.append(\n        base.pack_active_items(active_dislikes, base.DISLIKE_ITEMS, n_items)\n    )\n    state_counts.append((len(active_likes), len(active_dislikes)))\n    return len(liked_states) - 1\n\n\ndef causal_activity_features(\n    timestamps: np.ndarray,\n    items: np.ndarray,\n    organic: np.ndarray,\n    completion: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Compute the first four reviewed user features at every event cutoff.\"\"\"\n    length = len(items)\n    result = np.zeros((length, 4), dtype=np.float16)\n    if not length:\n        return result\n    left_rows = np.searchsorted(\n        timestamps,\n        timestamps - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n        side=\"left\",\n    )\n    rows = np.arange(length, dtype=np.int64)\n    counts = rows - left_rows + 1\n    organic_sum = np.cumsum(organic.astype(np.float64))\n    completion_sum = np.cumsum(np.minimum(completion, 100).astype(np.float64))\n    before_organic = np.where(\n        left_rows > 0, organic_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n    before_completion = np.where(\n        left_rows > 0, completion_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n\n    unique_counts = np.empty(length, dtype=np.int32)\n    frequencies: dict[int, int] = {}\n    left = 0\n    for right, raw_item in enumerate(items):\n        item = int(raw_item)\n        frequencies[item] = frequencies.get(item, 0) + 1\n        required_left = int(left_rows[right])\n        while left < required_left:\n            old_item = int(items[left])\n            remaining = frequencies[old_item] - 1\n            if remaining:\n                frequencies[old_item] = remaining\n            else:\n                del frequencies[old_item]\n            left += 1\n        unique_counts[right] = len(frequencies)\n\n    result[:, 0] = (np.log1p(counts) / 8.0).astype(np.float16)\n    result[:, 1] = (np.log1p(unique_counts) / 6.0).astype(np.float16)\n    result[:, 2] = (\n        (organic_sum - before_organic) / np.maximum(counts, 1)\n    ).astype(np.float16)\n    result[:, 3] = (\n        (completion_sum - before_completion)\n        / np.maximum(counts, 1)\n        / 100.0\n    ).astype(np.float16)\n    return result\n\n\ndef build_sequence_parts(\n    listens: base.ListenEvents,\n    explicit: base.ExplicitEvents,\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray, np.ndarray] | None:\n    qualifying = listens.completion_pct >= base.LISTEN_POSITIVE_THRESHOLD\n    timestamps = listens.timestamps[qualifying].astype(np.int64, copy=False)\n    items = listens.items[qualifying].astype(np.uint16, copy=False)\n    organic = listens.organic[qualifying].astype(np.float32, copy=False)\n    completion = listens.completion_pct[qualifying].astype(np.float32, copy=False)\n    if not len(items):\n\"\"\"Shared public-data primitives for the Yambda two-tower baseline.\"\"\"\nfrom __future__ import annotations\n\nimport sys\nfrom dataclasses import dataclass\nfrom pathlib import Path\nfrom typing import Iterator\n\nimport numpy as np\nimport pandas as pd\nimport pyarrow.parquet as pq\nimport torch\nfrom torch import nn\n\n\nDAY = 86_400\nTRAIN_END = 24_786_800\nVALIDATION_END = 25_393_400\nLISTEN_POSITIVE_THRESHOLD = 50\nPROFILE_LOOKBACK_DAYS = 120\nLIKE_ITEMS = 48\nDISLIKE_ITEMS = 24\nTOP_N = 100\n\n\n@dataclass(frozen=True)\nclass TowerConfig:\n    sequence_length: int = 100\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass ListenEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    organic: np.ndarray\n    completion_pct: np.ndarray\n\n\n@dataclass(frozen=True)\nclass ExplicitEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    channel: np.ndarray\n    active: np.ndarray\n    organic_like: np.ndarray\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef build_item_features(catalog: pd.DataFrame) -> np.ndarray:\n    \"\"\"Return four standardized features built only from the public catalog.\"\"\"\n    positives = catalog.positive_listens.to_numpy(dtype=np.float64, copy=False)\n    organic = catalog.organic_positive_listens.to_numpy(dtype=np.float64, copy=False)\n    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n    features = np.column_stack(\n        [\n            np.log1p(positives),\n            np.log1p(organic),\n            organic / np.maximum(positives, 1.0),\n            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n        ]\n    )\n    means = features.mean(axis=0, keepdims=True)\n    scales = np.maximum(features.std(axis=0, keepdims=True), 1.0e-6)\n    standardized = ((features - means) / scales).astype(np.float32)\n    if not np.isfinite(standardized).all():\n        raise RuntimeError(\"catalog features contain non-finite values\")\n    return standardized\n\n\ndef _combine_listen_chunks(parts: list[ListenEvents]) -> ListenEvents:\n    if len(parts) == 1:\n        return parts[0]\n    timestamps = np.concatenate([part.timestamps for part in parts])\n    items = np.concatenate([part.items for part in parts])\n    organic = np.concatenate([part.organic for part in parts])\n    completion = np.concatenate([part.completion_pct for part in parts])\n    order = np.argsort(timestamps, kind=\"stable\")\n    return ListenEvents(\n        timestamps=timestamps[order],\n        items=items[order],\n        organic=organic[order],\n        completion_pct=completion[order],\n    )\n\n\ndef iter_listen_users(\n    path: Path, item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Stream one uid-sorted public listen file one user at a time.\"\"\"\n    parquet = pq.ParquetFile(path)\n    pending_uid: int | None = None\n    pending: list[ListenEvents] = []\n    previous_uid = -1\n    for batch in parquet.iter_batches(\n        batch_size=750_000,\n        columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\", \"played_ratio_pct\"],\n    ):\n        frame = batch.to_pandas()\n        mapped = item_index.get_indexer(frame.item_id.to_numpy(dtype=np.int64))\n        keep = mapped >= 0\n        if not np.any(keep):\n            continue\n        uids = frame.uid.to_numpy(dtype=np.int64, copy=False)[keep]\n        timestamps = frame.timestamp.to_numpy(dtype=np.int64, copy=False)[keep]\n        items = mapped[keep].astype(np.int32, copy=False)\n        organic = frame.is_organic.to_numpy(dtype=np.uint8, copy=False)[keep]\n        completion = frame.played_ratio_pct.to_numpy(dtype=np.uint16, copy=False)[keep]\n        if np.any(uids[1:] < uids[:-1]):\n            raise RuntimeError(f\"{path.name} is not sorted by uid\")\n        boundaries = np.r_[\n            0,\n            np.flatnonzero(uids[1:] != uids[:-1]) + 1,\n            len(uids),\n        ]\n        for start, end in zip(boundaries[:-1], boundaries[1:]):\n            uid = int(uids[start])\n            part = ListenEvents(\n                timestamps[start:end].copy(),\n                items[start:end].copy(),\n                organic[start:end].copy(),\n                completion[start:end].copy(),\n            )\n            if pending_uid is None:\n                pending_uid = uid\n            elif uid != pending_uid:\n                if pending_uid < previous_uid:\n                    raise RuntimeError(f\"{path.name} user order regressed\")\n                yield pending_uid, _combine_listen_chunks(pending)\n                previous_uid = pending_uid\n                pending_uid = uid\n                pending = []\n            pending.append(part)\n    if pending_uid is not None:\n        yield pending_uid, _combine_listen_chunks(pending)\n\n\ndef merge_listen_streams(\n    paths: list[Path], item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Merge uid-sorted public listen files without materializing them.\"\"\"\n    streams = [iter(iter_listen_users(path, item_index)) for path in paths]\n    heads: list[tuple[int, ListenEvents] | None] = [\n        next(stream, None) for stream in streams\n    ]\n    while any(head is not None for head in heads):\n        uid = min(head[0] for head in heads if head is not None)\n        parts: list[ListenEvents] = []\n        for position, head in enumerate(heads):\n            if head is not None and head[0] == uid:\n                parts.append(head[1])\n                heads[position] = next(streams[position], None)\n        yield uid, _combine_listen_chunks(parts)\n\n\ndef load_explicit_events(\n    data: Path,\n    prefixes: tuple[str, ...],\n    item_index: pd.Index,\n) -> dict[int, ExplicitEvents]:\n    \"\"\"Load public explicit actions as chronological state changes.\"\"\"\n    specifications = (\n        (\"likes\", 0, 1, 0),\n        (\"unlikes\", 0, 0, 1),\n        (\"dislikes\", 1, 1, 0),\n        (\"undislikes\", 1, 0, 1),\n    )\n    parts: list[pd.DataFrame] = []\n    for family, channel, active, tie_priority in specifications:\n        for prefix in prefixes:\n            frame = pd.read_parquet(\n                data / f\"{prefix}_{family}.parquet\",\n                columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n            )\n            mapped = item_index.get_indexer(\n                frame.item_id.to_numpy(dtype=np.int64, copy=False)\n            )\n            keep = mapped >= 0\n            if not np.any(keep):\n                continue\n            retained = frame.loc[keep, [\"uid\", \"timestamp\", \"is_organic\"]].copy()\n            retained[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n            retained[\"channel\"] = np.int8(channel)\n            retained[\"active\"] = np.int8(active)\n            retained[\"tie_priority\"] = np.int8(tie_priority)\n            retained[\"organic_like\"] = np.int8(\n                family == \"likes\"\n            ) * retained.is_organic.astype(np.int8)\n            parts.append(retained.drop(columns=\"is_organic\"))\n    if not parts:\n        return {}\n    events = pd.concat(parts, ignore_index=True)\n    events = events.sort_values(\n        [\"uid\", \"timestamp\", \"tie_priority\"], kind=\"mergesort\"\n    ).reset_index(drop=True)\n    result: dict[int, ExplicitEvents] = {}\n    for uid, rows in events.groupby(\"uid\", sort=False):\n        result[int(uid)] = ExplicitEvents(\n            timestamps=rows.timestamp.to_numpy(dtype=np.int64, copy=True),\n            items=rows.item.to_numpy(dtype=np.int32, copy=True),\n            channel=rows.channel.to_numpy(dtype=np.int8, copy=True),\n            active=rows.active.to_numpy(dtype=np.int8, copy=True),\n            organic_like=rows.organic_like.to_numpy(dtype=np.int8, copy=True),\n        )\n    log(f\"loaded explicit events: rows={len(events):,} users={len(result):,}\")\n    return result\n\n\ndef empty_explicit_events() -> ExplicitEvents:\n    return ExplicitEvents(\n        timestamps=np.empty(0, dtype=np.int64),\n        items=np.empty(0, dtype=np.int32),\n        channel=np.empty(0, dtype=np.int8),\n        active=np.empty(0, dtype=np.int8),\n        organic_like=np.empty(0, dtype=np.int8),\n    )\n\n\ndef pack_active_items(\n    active: dict[int, int], width: int, padding_item: int\n) -> np.ndarray:\n    packed = np.full(width, padding_item, dtype=np.uint16)\n    if not active:\n        return packed\n    ordered = sorted(active.items(), key=lambda pair: (-pair[1], pair[0]))[:width]\n    packed[: len(ordered)] = np.fromiter(\n        (item for item, _ in ordered), dtype=np.uint16, count=len(ordered)\n    )\n    return packed\n\n\ndef load_inference_state(\n    path: Path,\n    item_index: pd.Index,\n    uids: np.ndarray,\n    n_items: int,\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:\n    \"\"\"Pack the task-provided active explicit state.\"\"\"\n    state = pd.read_parquet(path, columns=[\"uid\", \"item_id\", \"state\"])\n    mapped = item_index.get_indexer(state.item_id.to_numpy(dtype=np.int64))\n    keep = mapped >= 0\n    state = state.loc[keep, [\"uid\", \"state\"]].copy()\n    state[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n    user_rows = pd.Index(uids)\n    liked = np.full((len(uids), LIKE_ITEMS), n_items, dtype=np.uint16)\n    disliked = np.full((len(uids), DISLIKE_ITEMS), n_items, dtype=np.uint16)\n    like_counts = np.zeros(len(uids), dtype=np.int32)\n    dislike_counts = np.zeros(len(uids), dtype=np.int32)\n    for value, width, destination, counts in (\n        (\"liked\", LIKE_ITEMS, liked, like_counts),\n        (\"disliked\", DISLIKE_ITEMS, disliked, dislike_counts),\n    ):\n        selected = state[state.state == value]\n        for uid, rows in selected.groupby(\"uid\", sort=False):\n            row = int(user_rows.get_indexer([int(uid)])[0])\n            if row < 0:\n                continue\n            items = np.sort(rows.item.unique())\n            counts[row] = len(items)\n            retained = items[:width]\n            destination[row, : len(retained)] = retained.astype(np.uint16)\n    return liked, disliked, like_counts, dislike_counts\n\n\nclass SequentialTwoTower(nn.Module):\n    \"\"\"Order-sensitive user tower and independent catalog-aware item tower.\"\"\"\n\n    def __init__(self, item_features: np.ndarray, config: TowerConfig) -> None:\n        super().__init__()\n        n_items, n_item_features = item_features.shape\n        dim = config.embedding_dim\n        self.n_items = n_items\n        self.context_embedding = nn.Embedding(\n            n_items + 1, dim, padding_idx=n_items\n        )\n        self.event_projection = nn.Sequential(\n            nn.Linear(dim + 3, config.hidden_dim),\n            nn.GELU(),\n        )\n        self.sequence_encoder = nn.GRU(\n            input_size=config.hidden_dim,\n            hidden_size=dim,\n            num_layers=1,\n            batch_first=True,\n        )\n        self.user_tower = nn.Sequential(\n            nn.Linear(dim * 3 + 6, config.user_hidden_1),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_1, config.user_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_2, dim),\n        )\n        self.candidate_embedding = nn.Embedding(n_items, dim)\n        self.register_buffer(\n            \"item_features\", torch.from_numpy(item_features), persistent=True\n        )\n        self.item_tower = nn.Sequential(\n            nn.Linear(dim + n_item_features, config.item_hidden_1),\n            nn.GELU(),\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:39:54.185Z",
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            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
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          "timestamp": "2026-09-23T21:39:54.215Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-d449575b-b1dd-4be3-9396-716f22347b3d",
              "process_id": "57521",
              "command": [
                "/bin/sh",
                "-lc",
                "mkdir -p /app/solution && cp /task/current_model/train_current_model.py /app/solution/train_current_model.py && cp /task/current_model/two_tower_model.py /app/solution/two_tower_model.py && sed -n '1,260p' /app/solution/train_current_model.py && sed -n '1,320p' /app/solution/two_tower_model.py"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "mkdir -p /app/solution && cp /task/current_model/train_current_model.py /app/solution/train_current_model.py && cp /task/current_model/two_tower_model.py /app/solution/two_tower_model.py && sed -n '1,260p' /app/solution/train_current_model.py && sed -n '1,320p' /app/solution/two_tower_model.py"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "#!/usr/bin/env python3\n\"\"\"Train the Yambda windowed two-tower baseline.\n\nEvery catalog listen with at least 50 percent completion is a sequence token.\nWithin each selected chronological window, every adjacent target contributes a\nloss.  The fast default retains each user's most recent 128 training targets and\n16 held-out validation targets; passing zero for either cap restores the\nuncapped behavior for that side of the split.  A 100-step truncated-BPTT block\ncomputes all of its timestep losses and carries the detached GRU hidden state\ninto the next block.\n\nThe model is a pure two-tower retriever: no user-ID embedding, no output\nnormalization, raw dot-product retrieval, sample-weighted binary cross entropy,\nand 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\nselected adjacent target retains a nonzero weight. Only files under the supplied\npublic directory are read.\n\"\"\"\nfrom __future__ import annotations\n\nimport argparse\nimport json\nimport random\nimport sys\nimport time\nfrom dataclasses import asdict, dataclass\nfrom pathlib import Path\n\nimport numpy as np\nimport pandas as pd\nimport torch\nfrom torch import nn\nfrom torch.nn import functional as F\n\nimport two_tower_model as base\n\n\nCACHE_VERSION = 2\n\n\n@dataclass(frozen=True)\nclass Config:\n    bptt_steps: int = 100\n    user_batch_size: int = 64\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    loss_microbatch_size: int = 65_536\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    negative_filter_scope: str = \"full-training-history\"\n    target_weighting: str = \"organic-strong\"\n    ordinary_target_weight: float = 0.25\n    organic_strong_target_weight: float = 1.0\n    organic_like_target_weight: float = 3.0\n    discovery_horizon_days: int = 7\n    validation_fraction: float = 0.10\n    max_train_targets_per_user: int = 128\n    max_validation_targets_per_user: int = 16\n    early_stopping_patience: int = 1\n    early_stopping_min_delta: float = 1.0e-4\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass CandidateSet:\n    uids: np.ndarray\n    item_ids: np.ndarray\n    packed: np.ndarray\n\n    @classmethod\n    def read(cls, path: Path) -> \"CandidateSet\":\n        with np.load(path, allow_pickle=False) as artifact:\n            result = cls(\n                uids=artifact[\"uids\"].astype(np.int64, copy=True),\n                item_ids=artifact[\"item_ids\"].astype(np.int64, copy=True),\n                packed=artifact[\"packed_eligible\"].astype(np.uint8, copy=True),\n            )\n        expected = (len(result.uids), (len(result.item_ids) + 7) // 8)\n        if result.packed.shape != expected:\n            raise ValueError(\n                f\"invalid candidate artifact shape {result.packed.shape}; \"\n                f\"expected {expected}\"\n            )\n        return result\n\n\n@dataclass(frozen=True)\nclass SequenceData:\n    item_ids: np.ndarray\n    item_features: np.ndarray\n    user_ids: np.ndarray\n    offsets: np.ndarray\n    sequence_timestamps: np.ndarray\n    sequence_items: np.ndarray\n    event_features: np.ndarray\n    activity_features: np.ndarray\n    state_ids: np.ndarray\n    liked_states: np.ndarray\n    disliked_states: np.ndarray\n    state_counts: np.ndarray\n    inference_user_rows: np.ndarray\n    inference_liked_items: np.ndarray\n    inference_disliked_items: np.ndarray\n    inference_user_features: np.ndarray\n\n    @property\n    def lengths(self) -> np.ndarray:\n        return np.diff(self.offsets)\n\n    @property\n    def target_count(self) -> int:\n        return int(np.maximum(self.lengths - 1, 0).sum())\n\n\n@dataclass(frozen=True)\nclass TargetPartition:\n    \"\"\"A contiguous recent target window and its chronological BCE split.\"\"\"\n\n    window_starts: np.ndarray\n    training_counts: np.ndarray\n    validation_counts: np.ndarray\n    history_training_counts: np.ndarray\n\n    @property\n    def selected_count(self) -> int:\n        return int(self.training_counts.sum() + self.validation_counts.sum())\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef seed_everything(seed: int) -> None:\n    random.seed(seed)\n    np.random.seed(seed)\n    torch.manual_seed(seed)\n\n\ndef model_config(config: Config) -> base.TowerConfig:\n    \"\"\"Map the dense trainer configuration onto the unchanged tower.\"\"\"\n    return base.TowerConfig(\n        sequence_length=config.bptt_steps,\n        embedding_dim=config.embedding_dim,\n        hidden_dim=config.hidden_dim,\n        user_hidden_1=config.user_hidden_1,\n        user_hidden_2=config.user_hidden_2,\n        item_hidden_1=config.item_hidden_1,\n        item_hidden_2=config.item_hidden_2,\n        dropout=config.dropout,\n        epochs=config.epochs,\n        learning_rate=config.learning_rate,\n        weight_decay=config.weight_decay,\n        gradient_clip=config.gradient_clip,\n        uniform_negatives=config.uniform_negatives,\n        inbatch_negatives=config.inbatch_negatives,\n        inbatch_correction_power=config.inbatch_correction_power,\n        inbatch_correction_min=config.inbatch_correction_min,\n        inbatch_correction_max=config.inbatch_correction_max,\n        seed=config.seed,\n    )\n\n\ndef append_state_snapshot(\n    active_likes: dict[int, int],\n    active_dislikes: dict[int, int],\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> int:\n    liked_states.append(base.pack_active_items(active_likes, base.LIKE_ITEMS, n_items))\n    disliked_states.append(\n        base.pack_active_items(active_dislikes, base.DISLIKE_ITEMS, n_items)\n    )\n    state_counts.append((len(active_likes), len(active_dislikes)))\n    return len(liked_states) - 1\n\n\ndef causal_activity_features(\n    timestamps: np.ndarray,\n    items: np.ndarray,\n    organic: np.ndarray,\n    completion: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Compute the first four reviewed user features at every event cutoff.\"\"\"\n    length = len(items)\n    result = np.zeros((length, 4), dtype=np.float16)\n    if not length:\n        return result\n    left_rows = np.searchsorted(\n        timestamps,\n        timestamps - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n        side=\"left\",\n    )\n    rows = np.arange(length, dtype=np.int64)\n    counts = rows - left_rows + 1\n    organic_sum = np.cumsum(organic.astype(np.float64))\n    completion_sum = np.cumsum(np.minimum(completion, 100).astype(np.float64))\n    before_organic = np.where(\n        left_rows > 0, organic_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n    before_completion = np.where(\n        left_rows > 0, completion_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n\n    unique_counts = np.empty(length, dtype=np.int32)\n    frequencies: dict[int, int] = {}\n    left = 0\n    for right, raw_item in enumerate(items):\n        item = int(raw_item)\n        frequencies[item] = frequencies.get(item, 0) + 1\n        required_left = int(left_rows[right])\n        while left < required_left:\n            old_item = int(items[left])\n            remaining = frequencies[old_item] - 1\n            if remaining:\n                frequencies[old_item] = remaining\n            else:\n                del frequencies[old_item]\n            left += 1\n        unique_counts[right] = len(frequencies)\n\n    result[:, 0] = (np.log1p(counts) / 8.0).astype(np.float16)\n    result[:, 1] = (np.log1p(unique_counts) / 6.0).astype(np.float16)\n    result[:, 2] = (\n        (organic_sum - before_organic) / np.maximum(counts, 1)\n    ).astype(np.float16)\n    result[:, 3] = (\n        (completion_sum - before_completion)\n        / np.maximum(counts, 1)\n        / 100.0\n    ).astype(np.float16)\n    return result\n\n\ndef build_sequence_parts(\n    listens: base.ListenEvents,\n    explicit: base.ExplicitEvents,\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray, np.ndarray] | None:\n    qualifying = listens.completion_pct >= base.LISTEN_POSITIVE_THRESHOLD\n    timestamps = listens.timestamps[qualifying].astype(np.int64, copy=False)\n    items = listens.items[qualifying].astype(np.uint16, copy=False)\n    organic = listens.organic[qualifying].astype(np.float32, copy=False)\n    completion = listens.completion_pct[qualifying].astype(np.float32, copy=False)\n    if not len(items):\n\"\"\"Shared public-data primitives for the Yambda two-tower baseline.\"\"\"\nfrom __future__ import annotations\n\nimport sys\nfrom dataclasses import dataclass\nfrom pathlib import Path\nfrom typing import Iterator\n\nimport numpy as np\nimport pandas as pd\nimport pyarrow.parquet as pq\nimport torch\nfrom torch import nn\n\n\nDAY = 86_400\nTRAIN_END = 24_786_800\nVALIDATION_END = 25_393_400\nLISTEN_POSITIVE_THRESHOLD = 50\nPROFILE_LOOKBACK_DAYS = 120\nLIKE_ITEMS = 48\nDISLIKE_ITEMS = 24\nTOP_N = 100\n\n\n@dataclass(frozen=True)\nclass TowerConfig:\n    sequence_length: int = 100\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass ListenEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    organic: np.ndarray\n    completion_pct: np.ndarray\n\n\n@dataclass(frozen=True)\nclass ExplicitEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    channel: np.ndarray\n    active: np.ndarray\n    organic_like: np.ndarray\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef build_item_features(catalog: pd.DataFrame) -> np.ndarray:\n    \"\"\"Return four standardized features built only from the public catalog.\"\"\"\n    positives = catalog.positive_listens.to_numpy(dtype=np.float64, copy=False)\n    organic = catalog.organic_positive_listens.to_numpy(dtype=np.float64, copy=False)\n    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n    features = np.column_stack(\n        [\n            np.log1p(positives),\n            np.log1p(organic),\n            organic / np.maximum(positives, 1.0),\n            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n        ]\n    )\n    means = features.mean(axis=0, keepdims=True)\n    scales = np.maximum(features.std(axis=0, keepdims=True), 1.0e-6)\n    standardized = ((features - means) / scales).astype(np.float32)\n    if not np.isfinite(standardized).all():\n        raise RuntimeError(\"catalog features contain non-finite values\")\n    return standardized\n\n\ndef _combine_listen_chunks(parts: list[ListenEvents]) -> ListenEvents:\n    if len(parts) == 1:\n        return parts[0]\n    timestamps = np.concatenate([part.timestamps for part in parts])\n    items = np.concatenate([part.items for part in parts])\n    organic = np.concatenate([part.organic for part in parts])\n    completion = np.concatenate([part.completion_pct for part in parts])\n    order = np.argsort(timestamps, kind=\"stable\")\n    return ListenEvents(\n        timestamps=timestamps[order],\n        items=items[order],\n        organic=organic[order],\n        completion_pct=completion[order],\n    )\n\n\ndef iter_listen_users(\n    path: Path, item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Stream one uid-sorted public listen file one user at a time.\"\"\"\n    parquet = pq.ParquetFile(path)\n    pending_uid: int | None = None\n    pending: list[ListenEvents] = []\n    previous_uid = -1\n    for batch in parquet.iter_batches(\n        batch_size=750_000,\n        columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\", \"played_ratio_pct\"],\n    ):\n        frame = batch.to_pandas()\n        mapped = item_index.get_indexer(frame.item_id.to_numpy(dtype=np.int64))\n        keep = mapped >= 0\n        if not np.any(keep):\n            continue\n        uids = frame.uid.to_numpy(dtype=np.int64, copy=False)[keep]\n        timestamps = frame.timestamp.to_numpy(dtype=np.int64, copy=False)[keep]\n        items = mapped[keep].astype(np.int32, copy=False)\n        organic = frame.is_organic.to_numpy(dtype=np.uint8, copy=False)[keep]\n        completion = frame.played_ratio_pct.to_numpy(dtype=np.uint16, copy=False)[keep]\n        if np.any(uids[1:] < uids[:-1]):\n            raise RuntimeError(f\"{path.name} is not sorted by uid\")\n        boundaries = np.r_[\n            0,\n            np.flatnonzero(uids[1:] != uids[:-1]) + 1,\n            len(uids),\n        ]\n        for start, end in zip(boundaries[:-1], boundaries[1:]):\n            uid = int(uids[start])\n            part = ListenEvents(\n                timestamps[start:end].copy(),\n                items[start:end].copy(),\n                organic[start:end].copy(),\n                completion[start:end].copy(),\n            )\n            if pending_uid is None:\n                pending_uid = uid\n            elif uid != pending_uid:\n                if pending_uid < previous_uid:\n                    raise RuntimeError(f\"{path.name} user order regressed\")\n                yield pending_uid, _combine_listen_chunks(pending)\n                previous_uid = pending_uid\n                pending_uid = uid\n                pending = []\n            pending.append(part)\n    if pending_uid is not None:\n        yield pending_uid, _combine_listen_chunks(pending)\n\n\ndef merge_listen_streams(\n    paths: list[Path], item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Merge uid-sorted public listen files without materializing them.\"\"\"\n    streams = [iter(iter_listen_users(path, item_index)) for path in paths]\n    heads: list[tuple[int, ListenEvents] | None] = [\n        next(stream, None) for stream in streams\n    ]\n    while any(head is not None for head in heads):\n        uid = min(head[0] for head in heads if head is not None)\n        parts: list[ListenEvents] = []\n        for position, head in enumerate(heads):\n            if head is not None and head[0] == uid:\n                parts.append(head[1])\n                heads[position] = next(streams[position], None)\n        yield uid, _combine_listen_chunks(parts)\n\n\ndef load_explicit_events(\n    data: Path,\n    prefixes: tuple[str, ...],\n    item_index: pd.Index,\n) -> dict[int, ExplicitEvents]:\n    \"\"\"Load public explicit actions as chronological state changes.\"\"\"\n    specifications = (\n        (\"likes\", 0, 1, 0),\n        (\"unlikes\", 0, 0, 1),\n        (\"dislikes\", 1, 1, 0),\n        (\"undislikes\", 1, 0, 1),\n    )\n    parts: list[pd.DataFrame] = []\n    for family, channel, active, tie_priority in specifications:\n        for prefix in prefixes:\n            frame = pd.read_parquet(\n                data / f\"{prefix}_{family}.parquet\",\n                columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n            )\n            mapped = item_index.get_indexer(\n                frame.item_id.to_numpy(dtype=np.int64, copy=False)\n            )\n            keep = mapped >= 0\n            if not np.any(keep):\n                continue\n            retained = frame.loc[keep, [\"uid\", \"timestamp\", \"is_organic\"]].copy()\n            retained[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n            retained[\"channel\"] = np.int8(channel)\n            retained[\"active\"] = np.int8(active)\n            retained[\"tie_priority\"] = np.int8(tie_priority)\n            retained[\"organic_like\"] = np.int8(\n                family == \"likes\"\n            ) * retained.is_organic.astype(np.int8)\n            parts.append(retained.drop(columns=\"is_organic\"))\n    if not parts:\n        return {}\n    events = pd.concat(parts, ignore_index=True)\n    events = events.sort_values(\n        [\"uid\", \"timestamp\", \"tie_priority\"], kind=\"mergesort\"\n    ).reset_index(drop=True)\n    result: dict[int, ExplicitEvents] = {}\n    for uid, rows in events.groupby(\"uid\", sort=False):\n        result[int(uid)] = ExplicitEvents(\n            timestamps=rows.timestamp.to_numpy(dtype=np.int64, copy=True),\n            items=rows.item.to_numpy(dtype=np.int32, copy=True),\n            channel=rows.channel.to_numpy(dtype=np.int8, copy=True),\n            active=rows.active.to_numpy(dtype=np.int8, copy=True),\n            organic_like=rows.organic_like.to_numpy(dtype=np.int8, copy=True),\n        )\n    log(f\"loaded explicit events: rows={len(events):,} users={len(result):,}\")\n    return result\n\n\ndef empty_explicit_events() -> ExplicitEvents:\n    return ExplicitEvents(\n        timestamps=np.empty(0, dtype=np.int64),\n        items=np.empty(0, dtype=np.int32),\n        channel=np.empty(0, dtype=np.int8),\n        active=np.empty(0, dtype=np.int8),\n        organic_like=np.empty(0, dtype=np.int8),\n    )\n\n\ndef pack_active_items(\n    active: dict[int, int], width: int, padding_item: int\n) -> np.ndarray:\n    packed = np.full(width, padding_item, dtype=np.uint16)\n    if not active:\n        return packed\n    ordered = sorted(active.items(), key=lambda pair: (-pair[1], pair[0]))[:width]\n    packed[: len(ordered)] = np.fromiter(\n        (item for item, _ in ordered), dtype=np.uint16, count=len(ordered)\n    )\n    return packed\n\n\ndef load_inference_state(\n    path: Path,\n    item_index: pd.Index,\n    uids: np.ndarray,\n    n_items: int,\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:\n    \"\"\"Pack the task-provided active explicit state.\"\"\"\n    state = pd.read_parquet(path, columns=[\"uid\", \"item_id\", \"state\"])\n    mapped = item_index.get_indexer(state.item_id.to_numpy(dtype=np.int64))\n    keep = mapped >= 0\n    state = state.loc[keep, [\"uid\", \"state\"]].copy()\n    state[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n    user_rows = pd.Index(uids)\n    liked = np.full((len(uids), LIKE_ITEMS), n_items, dtype=np.uint16)\n    disliked = np.full((len(uids), DISLIKE_ITEMS), n_items, dtype=np.uint16)\n    like_counts = np.zeros(len(uids), dtype=np.int32)\n    dislike_counts = np.zeros(len(uids), dtype=np.int32)\n    for value, width, destination, counts in (\n        (\"liked\", LIKE_ITEMS, liked, like_counts),\n        (\"disliked\", DISLIKE_ITEMS, disliked, dislike_counts),\n    ):\n        selected = state[state.state == value]\n        for uid, rows in selected.groupby(\"uid\", sort=False):\n            row = int(user_rows.get_indexer([int(uid)])[0])\n            if row < 0:\n                continue\n            items = np.sort(rows.item.unique())\n            counts[row] = len(items)\n            retained = items[:width]\n            destination[row, : len(retained)] = retained.astype(np.uint16)\n    return liked, disliked, like_counts, dislike_counts\n\n\nclass SequentialTwoTower(nn.Module):\n    \"\"\"Order-sensitive user tower and independent catalog-aware item tower.\"\"\"\n\n    def __init__(self, item_features: np.ndarray, config: TowerConfig) -> None:\n        super().__init__()\n        n_items, n_item_features = item_features.shape\n        dim = config.embedding_dim\n        self.n_items = n_items\n        self.context_embedding = nn.Embedding(\n            n_items + 1, dim, padding_idx=n_items\n        )\n        self.event_projection = nn.Sequential(\n            nn.Linear(dim + 3, config.hidden_dim),\n            nn.GELU(),\n        )\n        self.sequence_encoder = nn.GRU(\n            input_size=config.hidden_dim,\n            hidden_size=dim,\n            num_layers=1,\n            batch_first=True,\n        )\n        self.user_tower = nn.Sequential(\n            nn.Linear(dim * 3 + 6, config.user_hidden_1),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_1, config.user_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_2, dim),\n        )\n        self.candidate_embedding = nn.Embedding(n_items, dim)\n        self.register_buffer(\n            \"item_features\", torch.from_numpy(item_features), persistent=True\n        )\n        self.item_tower = nn.Sequential(\n            nn.Linear(dim + n_item_features, config.item_hidden_1),\n            nn.GELU(),\n",
              "stderr": "",
              "aggregated_output": "#!/usr/bin/env python3\n\"\"\"Train the Yambda windowed two-tower baseline.\n\nEvery catalog listen with at least 50 percent completion is a sequence token.\nWithin each selected chronological window, every adjacent target contributes a\nloss.  The fast default retains each user's most recent 128 training targets and\n16 held-out validation targets; passing zero for either cap restores the\nuncapped behavior for that side of the split.  A 100-step truncated-BPTT block\ncomputes all of its timestep losses and carries the detached GRU hidden state\ninto the next block.\n\nThe model is a pure two-tower retriever: no user-ID embedding, no output\nnormalization, raw dot-product retrieval, sample-weighted binary cross entropy,\nand 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\nselected adjacent target retains a nonzero weight. Only files under the supplied\npublic directory are read.\n\"\"\"\nfrom __future__ import annotations\n\nimport argparse\nimport json\nimport random\nimport sys\nimport time\nfrom dataclasses import asdict, dataclass\nfrom pathlib import Path\n\nimport numpy as np\nimport pandas as pd\nimport torch\nfrom torch import nn\nfrom torch.nn import functional as F\n\nimport two_tower_model as base\n\n\nCACHE_VERSION = 2\n\n\n@dataclass(frozen=True)\nclass Config:\n    bptt_steps: int = 100\n    user_batch_size: int = 64\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    loss_microbatch_size: int = 65_536\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    negative_filter_scope: str = \"full-training-history\"\n    target_weighting: str = \"organic-strong\"\n    ordinary_target_weight: float = 0.25\n    organic_strong_target_weight: float = 1.0\n    organic_like_target_weight: float = 3.0\n    discovery_horizon_days: int = 7\n    validation_fraction: float = 0.10\n    max_train_targets_per_user: int = 128\n    max_validation_targets_per_user: int = 16\n    early_stopping_patience: int = 1\n    early_stopping_min_delta: float = 1.0e-4\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass CandidateSet:\n    uids: np.ndarray\n    item_ids: np.ndarray\n    packed: np.ndarray\n\n    @classmethod\n    def read(cls, path: Path) -> \"CandidateSet\":\n        with np.load(path, allow_pickle=False) as artifact:\n            result = cls(\n                uids=artifact[\"uids\"].astype(np.int64, copy=True),\n                item_ids=artifact[\"item_ids\"].astype(np.int64, copy=True),\n                packed=artifact[\"packed_eligible\"].astype(np.uint8, copy=True),\n            )\n        expected = (len(result.uids), (len(result.item_ids) + 7) // 8)\n        if result.packed.shape != expected:\n            raise ValueError(\n                f\"invalid candidate artifact shape {result.packed.shape}; \"\n                f\"expected {expected}\"\n            )\n        return result\n\n\n@dataclass(frozen=True)\nclass SequenceData:\n    item_ids: np.ndarray\n    item_features: np.ndarray\n    user_ids: np.ndarray\n    offsets: np.ndarray\n    sequence_timestamps: np.ndarray\n    sequence_items: np.ndarray\n    event_features: np.ndarray\n    activity_features: np.ndarray\n    state_ids: np.ndarray\n    liked_states: np.ndarray\n    disliked_states: np.ndarray\n    state_counts: np.ndarray\n    inference_user_rows: np.ndarray\n    inference_liked_items: np.ndarray\n    inference_disliked_items: np.ndarray\n    inference_user_features: np.ndarray\n\n    @property\n    def lengths(self) -> np.ndarray:\n        return np.diff(self.offsets)\n\n    @property\n    def target_count(self) -> int:\n        return int(np.maximum(self.lengths - 1, 0).sum())\n\n\n@dataclass(frozen=True)\nclass TargetPartition:\n    \"\"\"A contiguous recent target window and its chronological BCE split.\"\"\"\n\n    window_starts: np.ndarray\n    training_counts: np.ndarray\n    validation_counts: np.ndarray\n    history_training_counts: np.ndarray\n\n    @property\n    def selected_count(self) -> int:\n        return int(self.training_counts.sum() + self.validation_counts.sum())\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef seed_everything(seed: int) -> None:\n    random.seed(seed)\n    np.random.seed(seed)\n    torch.manual_seed(seed)\n\n\ndef model_config(config: Config) -> base.TowerConfig:\n    \"\"\"Map the dense trainer configuration onto the unchanged tower.\"\"\"\n    return base.TowerConfig(\n        sequence_length=config.bptt_steps,\n        embedding_dim=config.embedding_dim,\n        hidden_dim=config.hidden_dim,\n        user_hidden_1=config.user_hidden_1,\n        user_hidden_2=config.user_hidden_2,\n        item_hidden_1=config.item_hidden_1,\n        item_hidden_2=config.item_hidden_2,\n        dropout=config.dropout,\n        epochs=config.epochs,\n        learning_rate=config.learning_rate,\n        weight_decay=config.weight_decay,\n        gradient_clip=config.gradient_clip,\n        uniform_negatives=config.uniform_negatives,\n        inbatch_negatives=config.inbatch_negatives,\n        inbatch_correction_power=config.inbatch_correction_power,\n        inbatch_correction_min=config.inbatch_correction_min,\n        inbatch_correction_max=config.inbatch_correction_max,\n        seed=config.seed,\n    )\n\n\ndef append_state_snapshot(\n    active_likes: dict[int, int],\n    active_dislikes: dict[int, int],\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> int:\n    liked_states.append(base.pack_active_items(active_likes, base.LIKE_ITEMS, n_items))\n    disliked_states.append(\n        base.pack_active_items(active_dislikes, base.DISLIKE_ITEMS, n_items)\n    )\n    state_counts.append((len(active_likes), len(active_dislikes)))\n    return len(liked_states) - 1\n\n\ndef causal_activity_features(\n    timestamps: np.ndarray,\n    items: np.ndarray,\n    organic: np.ndarray,\n    completion: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Compute the first four reviewed user features at every event cutoff.\"\"\"\n    length = len(items)\n    result = np.zeros((length, 4), dtype=np.float16)\n    if not length:\n        return result\n    left_rows = np.searchsorted(\n        timestamps,\n        timestamps - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n        side=\"left\",\n    )\n    rows = np.arange(length, dtype=np.int64)\n    counts = rows - left_rows + 1\n    organic_sum = np.cumsum(organic.astype(np.float64))\n    completion_sum = np.cumsum(np.minimum(completion, 100).astype(np.float64))\n    before_organic = np.where(\n        left_rows > 0, organic_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n    before_completion = np.where(\n        left_rows > 0, completion_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n\n    unique_counts = np.empty(length, dtype=np.int32)\n    frequencies: dict[int, int] = {}\n    left = 0\n    for right, raw_item in enumerate(items):\n        item = int(raw_item)\n        frequencies[item] = frequencies.get(item, 0) + 1\n        required_left = int(left_rows[right])\n        while left < required_left:\n            old_item = int(items[left])\n            remaining = frequencies[old_item] - 1\n            if remaining:\n                frequencies[old_item] = remaining\n            else:\n                del frequencies[old_item]\n            left += 1\n        unique_counts[right] = len(frequencies)\n\n    result[:, 0] = (np.log1p(counts) / 8.0).astype(np.float16)\n    result[:, 1] = (np.log1p(unique_counts) / 6.0).astype(np.float16)\n    result[:, 2] = (\n        (organic_sum - before_organic) / np.maximum(counts, 1)\n    ).astype(np.float16)\n    result[:, 3] = (\n        (completion_sum - before_completion)\n        / np.maximum(counts, 1)\n        / 100.0\n    ).astype(np.float16)\n    return result\n\n\ndef build_sequence_parts(\n    listens: base.ListenEvents,\n    explicit: base.ExplicitEvents,\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray, np.ndarray] | None:\n    qualifying = listens.completion_pct >= base.LISTEN_POSITIVE_THRESHOLD\n    timestamps = listens.timestamps[qualifying].astype(np.int64, copy=False)\n    items = listens.items[qualifying].astype(np.uint16, copy=False)\n    organic = listens.organic[qualifying].astype(np.float32, copy=False)\n    completion = listens.completion_pct[qualifying].astype(np.float32, copy=False)\n    if not len(items):\n\"\"\"Shared public-data primitives for the Yambda two-tower baseline.\"\"\"\nfrom __future__ import annotations\n\nimport sys\nfrom dataclasses import dataclass\nfrom pathlib import Path\nfrom typing import Iterator\n\nimport numpy as np\nimport pandas as pd\nimport pyarrow.parquet as pq\nimport torch\nfrom torch import nn\n\n\nDAY = 86_400\nTRAIN_END = 24_786_800\nVALIDATION_END = 25_393_400\nLISTEN_POSITIVE_THRESHOLD = 50\nPROFILE_LOOKBACK_DAYS = 120\nLIKE_ITEMS = 48\nDISLIKE_ITEMS = 24\nTOP_N = 100\n\n\n@dataclass(frozen=True)\nclass TowerConfig:\n    sequence_length: int = 100\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass ListenEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    organic: np.ndarray\n    completion_pct: np.ndarray\n\n\n@dataclass(frozen=True)\nclass ExplicitEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    channel: np.ndarray\n    active: np.ndarray\n    organic_like: np.ndarray\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef build_item_features(catalog: pd.DataFrame) -> np.ndarray:\n    \"\"\"Return four standardized features built only from the public catalog.\"\"\"\n    positives = catalog.positive_listens.to_numpy(dtype=np.float64, copy=False)\n    organic = catalog.organic_positive_listens.to_numpy(dtype=np.float64, copy=False)\n    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n    features = np.column_stack(\n        [\n            np.log1p(positives),\n            np.log1p(organic),\n            organic / np.maximum(positives, 1.0),\n            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n        ]\n    )\n    means = features.mean(axis=0, keepdims=True)\n    scales = np.maximum(features.std(axis=0, keepdims=True), 1.0e-6)\n    standardized = ((features - means) / scales).astype(np.float32)\n    if not np.isfinite(standardized).all():\n        raise RuntimeError(\"catalog features contain non-finite values\")\n    return standardized\n\n\ndef _combine_listen_chunks(parts: list[ListenEvents]) -> ListenEvents:\n    if len(parts) == 1:\n        return parts[0]\n    timestamps = np.concatenate([part.timestamps for part in parts])\n    items = np.concatenate([part.items for part in parts])\n    organic = np.concatenate([part.organic for part in parts])\n    completion = np.concatenate([part.completion_pct for part in parts])\n    order = np.argsort(timestamps, kind=\"stable\")\n    return ListenEvents(\n        timestamps=timestamps[order],\n        items=items[order],\n        organic=organic[order],\n        completion_pct=completion[order],\n    )\n\n\ndef iter_listen_users(\n    path: Path, item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Stream one uid-sorted public listen file one user at a time.\"\"\"\n    parquet = pq.ParquetFile(path)\n    pending_uid: int | None = None\n    pending: list[ListenEvents] = []\n    previous_uid = -1\n    for batch in parquet.iter_batches(\n        batch_size=750_000,\n        columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\", \"played_ratio_pct\"],\n    ):\n        frame = batch.to_pandas()\n        mapped = item_index.get_indexer(frame.item_id.to_numpy(dtype=np.int64))\n        keep = mapped >= 0\n        if not np.any(keep):\n            continue\n        uids = frame.uid.to_numpy(dtype=np.int64, copy=False)[keep]\n        timestamps = frame.timestamp.to_numpy(dtype=np.int64, copy=False)[keep]\n        items = mapped[keep].astype(np.int32, copy=False)\n        organic = frame.is_organic.to_numpy(dtype=np.uint8, copy=False)[keep]\n        completion = frame.played_ratio_pct.to_numpy(dtype=np.uint16, copy=False)[keep]\n        if np.any(uids[1:] < uids[:-1]):\n            raise RuntimeError(f\"{path.name} is not sorted by uid\")\n        boundaries = np.r_[\n            0,\n            np.flatnonzero(uids[1:] != uids[:-1]) + 1,\n            len(uids),\n        ]\n        for start, end in zip(boundaries[:-1], boundaries[1:]):\n            uid = int(uids[start])\n            part = ListenEvents(\n                timestamps[start:end].copy(),\n                items[start:end].copy(),\n                organic[start:end].copy(),\n                completion[start:end].copy(),\n            )\n            if pending_uid is None:\n                pending_uid = uid\n            elif uid != pending_uid:\n                if pending_uid < previous_uid:\n                    raise RuntimeError(f\"{path.name} user order regressed\")\n                yield pending_uid, _combine_listen_chunks(pending)\n                previous_uid = pending_uid\n                pending_uid = uid\n                pending = []\n            pending.append(part)\n    if pending_uid is not None:\n        yield pending_uid, _combine_listen_chunks(pending)\n\n\ndef merge_listen_streams(\n    paths: list[Path], item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Merge uid-sorted public listen files without materializing them.\"\"\"\n    streams = [iter(iter_listen_users(path, item_index)) for path in paths]\n    heads: list[tuple[int, ListenEvents] | None] = [\n        next(stream, None) for stream in streams\n    ]\n    while any(head is not None for head in heads):\n        uid = min(head[0] for head in heads if head is not None)\n        parts: list[ListenEvents] = []\n        for position, head in enumerate(heads):\n            if head is not None and head[0] == uid:\n                parts.append(head[1])\n                heads[position] = next(streams[position], None)\n        yield uid, _combine_listen_chunks(parts)\n\n\ndef load_explicit_events(\n    data: Path,\n    prefixes: tuple[str, ...],\n    item_index: pd.Index,\n) -> dict[int, ExplicitEvents]:\n    \"\"\"Load public explicit actions as chronological state changes.\"\"\"\n    specifications = (\n        (\"likes\", 0, 1, 0),\n        (\"unlikes\", 0, 0, 1),\n        (\"dislikes\", 1, 1, 0),\n        (\"undislikes\", 1, 0, 1),\n    )\n    parts: list[pd.DataFrame] = []\n    for family, channel, active, tie_priority in specifications:\n        for prefix in prefixes:\n            frame = pd.read_parquet(\n                data / f\"{prefix}_{family}.parquet\",\n                columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n            )\n            mapped = item_index.get_indexer(\n                frame.item_id.to_numpy(dtype=np.int64, copy=False)\n            )\n            keep = mapped >= 0\n            if not np.any(keep):\n                continue\n            retained = frame.loc[keep, [\"uid\", \"timestamp\", \"is_organic\"]].copy()\n            retained[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n            retained[\"channel\"] = np.int8(channel)\n            retained[\"active\"] = np.int8(active)\n            retained[\"tie_priority\"] = np.int8(tie_priority)\n            retained[\"organic_like\"] = np.int8(\n                family == \"likes\"\n            ) * retained.is_organic.astype(np.int8)\n            parts.append(retained.drop(columns=\"is_organic\"))\n    if not parts:\n        return {}\n    events = pd.concat(parts, ignore_index=True)\n    events = events.sort_values(\n        [\"uid\", \"timestamp\", \"tie_priority\"], kind=\"mergesort\"\n    ).reset_index(drop=True)\n    result: dict[int, ExplicitEvents] = {}\n    for uid, rows in events.groupby(\"uid\", sort=False):\n        result[int(uid)] = ExplicitEvents(\n            timestamps=rows.timestamp.to_numpy(dtype=np.int64, copy=True),\n            items=rows.item.to_numpy(dtype=np.int32, copy=True),\n            channel=rows.channel.to_numpy(dtype=np.int8, copy=True),\n            active=rows.active.to_numpy(dtype=np.int8, copy=True),\n            organic_like=rows.organic_like.to_numpy(dtype=np.int8, copy=True),\n        )\n    log(f\"loaded explicit events: rows={len(events):,} users={len(result):,}\")\n    return result\n\n\ndef empty_explicit_events() -> ExplicitEvents:\n    return ExplicitEvents(\n        timestamps=np.empty(0, dtype=np.int64),\n        items=np.empty(0, dtype=np.int32),\n        channel=np.empty(0, dtype=np.int8),\n        active=np.empty(0, dtype=np.int8),\n        organic_like=np.empty(0, dtype=np.int8),\n    )\n\n\ndef pack_active_items(\n    active: dict[int, int], width: int, padding_item: int\n) -> np.ndarray:\n    packed = np.full(width, padding_item, dtype=np.uint16)\n    if not active:\n        return packed\n    ordered = sorted(active.items(), key=lambda pair: (-pair[1], pair[0]))[:width]\n    packed[: len(ordered)] = np.fromiter(\n        (item for item, _ in ordered), dtype=np.uint16, count=len(ordered)\n    )\n    return packed\n\n\ndef load_inference_state(\n    path: Path,\n    item_index: pd.Index,\n    uids: np.ndarray,\n    n_items: int,\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:\n    \"\"\"Pack the task-provided active explicit state.\"\"\"\n    state = pd.read_parquet(path, columns=[\"uid\", \"item_id\", \"state\"])\n    mapped = item_index.get_indexer(state.item_id.to_numpy(dtype=np.int64))\n    keep = mapped >= 0\n    state = state.loc[keep, [\"uid\", \"state\"]].copy()\n    state[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n    user_rows = pd.Index(uids)\n    liked = np.full((len(uids), LIKE_ITEMS), n_items, dtype=np.uint16)\n    disliked = np.full((len(uids), DISLIKE_ITEMS), n_items, dtype=np.uint16)\n    like_counts = np.zeros(len(uids), dtype=np.int32)\n    dislike_counts = np.zeros(len(uids), dtype=np.int32)\n    for value, width, destination, counts in (\n        (\"liked\", LIKE_ITEMS, liked, like_counts),\n        (\"disliked\", DISLIKE_ITEMS, disliked, dislike_counts),\n    ):\n        selected = state[state.state == value]\n        for uid, rows in selected.groupby(\"uid\", sort=False):\n            row = int(user_rows.get_indexer([int(uid)])[0])\n            if row < 0:\n                continue\n            items = np.sort(rows.item.unique())\n            counts[row] = len(items)\n            retained = items[:width]\n            destination[row, : len(retained)] = retained.astype(np.uint16)\n    return liked, disliked, like_counts, dislike_counts\n\n\nclass SequentialTwoTower(nn.Module):\n    \"\"\"Order-sensitive user tower and independent catalog-aware item tower.\"\"\"\n\n    def __init__(self, item_features: np.ndarray, config: TowerConfig) -> None:\n        super().__init__()\n        n_items, n_item_features = item_features.shape\n        dim = config.embedding_dim\n        self.n_items = n_items\n        self.context_embedding = nn.Embedding(\n            n_items + 1, dim, padding_idx=n_items\n        )\n        self.event_projection = nn.Sequential(\n            nn.Linear(dim + 3, config.hidden_dim),\n            nn.GELU(),\n        )\n        self.sequence_encoder = nn.GRU(\n            input_size=config.hidden_dim,\n            hidden_size=dim,\n            num_layers=1,\n            batch_first=True,\n        )\n        self.user_tower = nn.Sequential(\n            nn.Linear(dim * 3 + 6, config.user_hidden_1),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_1, config.user_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_2, dim),\n        )\n        self.candidate_embedding = nn.Embedding(n_items, dim)\n        self.register_buffer(\n            \"item_features\", torch.from_numpy(item_features), persistent=True\n        )\n        self.item_tower = nn.Sequential(\n            nn.Linear(dim + n_item_features, config.item_hidden_1),\n            nn.GELU(),\n",
              "exit_code": 0,
              "duration": {
                "secs": 0,
                "nanos": 3980
              },
              "formatted_output": "#!/usr/bin/env python3\n\"\"\"Train the Yambda windowed two-tower baseline.\n\nEvery catalog listen with at least 50 percent completion is a sequence token.\nWithin each selected chronological window, every adjacent target contributes a\nloss.  The fast default retains each user's most recent 128 training targets and\n16 held-out validation targets; passing zero for either cap restores the\nuncapped behavior for that side of the split.  A 100-step truncated-BPTT block\ncomputes all of its timestep losses and carries the detached GRU hidden state\ninto the next block.\n\nThe model is a pure two-tower retriever: no user-ID embedding, no output\nnormalization, raw dot-product retrieval, sample-weighted binary cross entropy,\nand 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\nselected adjacent target retains a nonzero weight. Only files under the supplied\npublic directory are read.\n\"\"\"\nfrom __future__ import annotations\n\nimport argparse\nimport json\nimport random\nimport sys\nimport time\nfrom dataclasses import asdict, dataclass\nfrom pathlib import Path\n\nimport numpy as np\nimport pandas as pd\nimport torch\nfrom torch import nn\nfrom torch.nn import functional as F\n\nimport two_tower_model as base\n\n\nCACHE_VERSION = 2\n\n\n@dataclass(frozen=True)\nclass Config:\n    bptt_steps: int = 100\n    user_batch_size: int = 64\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    loss_microbatch_size: int = 65_536\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    negative_filter_scope: str = \"full-training-history\"\n    target_weighting: str = \"organic-strong\"\n    ordinary_target_weight: float = 0.25\n    organic_strong_target_weight: float = 1.0\n    organic_like_target_weight: float = 3.0\n    discovery_horizon_days: int = 7\n    validation_fraction: float = 0.10\n    max_train_targets_per_user: int = 128\n    max_validation_targets_per_user: int = 16\n    early_stopping_patience: int = 1\n    early_stopping_min_delta: float = 1.0e-4\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass CandidateSet:\n    uids: np.ndarray\n    item_ids: np.ndarray\n    packed: np.ndarray\n\n    @classmethod\n    def read(cls, path: Path) -> \"CandidateSet\":\n        with np.load(path, allow_pickle=False) as artifact:\n            result = cls(\n                uids=artifact[\"uids\"].astype(np.int64, copy=True),\n                item_ids=artifact[\"item_ids\"].astype(np.int64, copy=True),\n                packed=artifact[\"packed_eligible\"].astype(np.uint8, copy=True),\n            )\n        expected = (len(result.uids), (len(result.item_ids) + 7) // 8)\n        if result.packed.shape != expected:\n            raise ValueError(\n                f\"invalid candidate artifact shape {result.packed.shape}; \"\n                f\"expected {expected}\"\n            )\n        return result\n\n\n@dataclass(frozen=True)\nclass SequenceData:\n    item_ids: np.ndarray\n    item_features: np.ndarray\n    user_ids: np.ndarray\n    offsets: np.ndarray\n    sequence_timestamps: np.ndarray\n    sequence_items: np.ndarray\n    event_features: np.ndarray\n    activity_features: np.ndarray\n    state_ids: np.ndarray\n    liked_states: np.ndarray\n    disliked_states: np.ndarray\n    state_counts: np.ndarray\n    inference_user_rows: np.ndarray\n    inference_liked_items: np.ndarray\n    inference_disliked_items: np.ndarray\n    inference_user_features: np.ndarray\n\n    @property\n    def lengths(self) -> np.ndarray:\n        return np.diff(self.offsets)\n\n    @property\n    def target_count(self) -> int:\n        return int(np.maximum(self.lengths - 1, 0).sum())\n\n\n@dataclass(frozen=True)\nclass TargetPartition:\n    \"\"\"A contiguous recent target window and its chronological BCE split.\"\"\"\n\n    window_starts: np.ndarray\n    training_counts: np.ndarray\n    validation_counts: np.ndarray\n    history_training_counts: np.ndarray\n\n    @property\n    def selected_count(self) -> int:\n        return int(self.training_counts.sum() + self.validation_counts.sum())\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef seed_everything(seed: int) -> None:\n    random.seed(seed)\n    np.random.seed(seed)\n    torch.manual_seed(seed)\n\n\ndef model_config(config: Config) -> base.TowerConfig:\n    \"\"\"Map the dense trainer configuration onto the unchanged tower.\"\"\"\n    return base.TowerConfig(\n        sequence_length=config.bptt_steps,\n        embedding_dim=config.embedding_dim,\n        hidden_dim=config.hidden_dim,\n        user_hidden_1=config.user_hidden_1,\n        user_hidden_2=config.user_hidden_2,\n        item_hidden_1=config.item_hidden_1,\n        item_hidden_2=config.item_hidden_2,\n        dropout=config.dropout,\n        epochs=config.epochs,\n        learning_rate=config.learning_rate,\n        weight_decay=config.weight_decay,\n        gradient_clip=config.gradient_clip,\n        uniform_negatives=config.uniform_negatives,\n        inbatch_negatives=config.inbatch_negatives,\n        inbatch_correction_power=config.inbatch_correction_power,\n        inbatch_correction_min=config.inbatch_correction_min,\n        inbatch_correction_max=config.inbatch_correction_max,\n        seed=config.seed,\n    )\n\n\ndef append_state_snapshot(\n    active_likes: dict[int, int],\n    active_dislikes: dict[int, int],\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> int:\n    liked_states.append(base.pack_active_items(active_likes, base.LIKE_ITEMS, n_items))\n    disliked_states.append(\n        base.pack_active_items(active_dislikes, base.DISLIKE_ITEMS, n_items)\n    )\n    state_counts.append((len(active_likes), len(active_dislikes)))\n    return len(liked_states) - 1\n\n\ndef causal_activity_features(\n    timestamps: np.ndarray,\n    items: np.ndarray,\n    organic: np.ndarray,\n    completion: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Compute the first four reviewed user features at every event cutoff.\"\"\"\n    length = len(items)\n    result = np.zeros((length, 4), dtype=np.float16)\n    if not length:\n        return result\n    left_rows = np.searchsorted(\n        timestamps,\n        timestamps - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n        side=\"left\",\n    )\n    rows = np.arange(length, dtype=np.int64)\n    counts = rows - left_rows + 1\n    organic_sum = np.cumsum(organic.astype(np.float64))\n    completion_sum = np.cumsum(np.minimum(completion, 100).astype(np.float64))\n    before_organic = np.where(\n        left_rows > 0, organic_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n    before_completion = np.where(\n        left_rows > 0, completion_sum[np.maximum(left_rows - 1, 0)], 0.0\n    )\n\n    unique_counts = np.empty(length, dtype=np.int32)\n    frequencies: dict[int, int] = {}\n    left = 0\n    for right, raw_item in enumerate(items):\n        item = int(raw_item)\n        frequencies[item] = frequencies.get(item, 0) + 1\n        required_left = int(left_rows[right])\n        while left < required_left:\n            old_item = int(items[left])\n            remaining = frequencies[old_item] - 1\n            if remaining:\n                frequencies[old_item] = remaining\n            else:\n                del frequencies[old_item]\n            left += 1\n        unique_counts[right] = len(frequencies)\n\n    result[:, 0] = (np.log1p(counts) / 8.0).astype(np.float16)\n    result[:, 1] = (np.log1p(unique_counts) / 6.0).astype(np.float16)\n    result[:, 2] = (\n        (organic_sum - before_organic) / np.maximum(counts, 1)\n    ).astype(np.float16)\n    result[:, 3] = (\n        (completion_sum - before_completion)\n        / np.maximum(counts, 1)\n        / 100.0\n    ).astype(np.float16)\n    return result\n\n\ndef build_sequence_parts(\n    listens: base.ListenEvents,\n    explicit: base.ExplicitEvents,\n    n_items: int,\n    liked_states: list[np.ndarray],\n    disliked_states: list[np.ndarray],\n    state_counts: list[tuple[int, int]],\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray, np.ndarray] | None:\n    qualifying = listens.completion_pct >= base.LISTEN_POSITIVE_THRESHOLD\n    timestamps = listens.timestamps[qualifying].astype(np.int64, copy=False)\n    items = listens.items[qualifying].astype(np.uint16, copy=False)\n    organic = listens.organic[qualifying].astype(np.float32, copy=False)\n    completion = listens.completion_pct[qualifying].astype(np.float32, copy=False)\n    if not len(items):\n\"\"\"Shared public-data primitives for the Yambda two-tower baseline.\"\"\"\nfrom __future__ import annotations\n\nimport sys\nfrom dataclasses import dataclass\nfrom pathlib import Path\nfrom typing import Iterator\n\nimport numpy as np\nimport pandas as pd\nimport pyarrow.parquet as pq\nimport torch\nfrom torch import nn\n\n\nDAY = 86_400\nTRAIN_END = 24_786_800\nVALIDATION_END = 25_393_400\nLISTEN_POSITIVE_THRESHOLD = 50\nPROFILE_LOOKBACK_DAYS = 120\nLIKE_ITEMS = 48\nDISLIKE_ITEMS = 24\nTOP_N = 100\n\n\n@dataclass(frozen=True)\nclass TowerConfig:\n    sequence_length: int = 100\n    embedding_dim: int = 192\n    hidden_dim: int = 192\n    user_hidden_1: int = 512\n    user_hidden_2: int = 256\n    item_hidden_1: int = 512\n    item_hidden_2: int = 256\n    dropout: float = 0.05\n    epochs: int = 1\n    learning_rate: float = 1.0e-3\n    weight_decay: float = 1.0e-5\n    gradient_clip: float = 2.0\n    uniform_negatives: int = 24\n    inbatch_negatives: int = 8\n    inbatch_correction_power: float = 0.5\n    inbatch_correction_min: float = 0.25\n    inbatch_correction_max: float = 4.0\n    seed: int = 29\n\n\n@dataclass(frozen=True)\nclass ListenEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    organic: np.ndarray\n    completion_pct: np.ndarray\n\n\n@dataclass(frozen=True)\nclass ExplicitEvents:\n    timestamps: np.ndarray\n    items: np.ndarray\n    channel: np.ndarray\n    active: np.ndarray\n    organic_like: np.ndarray\n\n\ndef log(message: str) -> None:\n    print(message, file=sys.stderr, flush=True)\n\n\ndef build_item_features(catalog: pd.DataFrame) -> np.ndarray:\n    \"\"\"Return four standardized features built only from the public catalog.\"\"\"\n    positives = catalog.positive_listens.to_numpy(dtype=np.float64, copy=False)\n    organic = catalog.organic_positive_listens.to_numpy(dtype=np.float64, copy=False)\n    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n    features = np.column_stack(\n        [\n            np.log1p(positives),\n            np.log1p(organic),\n            organic / np.maximum(positives, 1.0),\n            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n        ]\n    )\n    means = features.mean(axis=0, keepdims=True)\n    scales = np.maximum(features.std(axis=0, keepdims=True), 1.0e-6)\n    standardized = ((features - means) / scales).astype(np.float32)\n    if not np.isfinite(standardized).all():\n        raise RuntimeError(\"catalog features contain non-finite values\")\n    return standardized\n\n\ndef _combine_listen_chunks(parts: list[ListenEvents]) -> ListenEvents:\n    if len(parts) == 1:\n        return parts[0]\n    timestamps = np.concatenate([part.timestamps for part in parts])\n    items = np.concatenate([part.items for part in parts])\n    organic = np.concatenate([part.organic for part in parts])\n    completion = np.concatenate([part.completion_pct for part in parts])\n    order = np.argsort(timestamps, kind=\"stable\")\n    return ListenEvents(\n        timestamps=timestamps[order],\n        items=items[order],\n        organic=organic[order],\n        completion_pct=completion[order],\n    )\n\n\ndef iter_listen_users(\n    path: Path, item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Stream one uid-sorted public listen file one user at a time.\"\"\"\n    parquet = pq.ParquetFile(path)\n    pending_uid: int | None = None\n    pending: list[ListenEvents] = []\n    previous_uid = -1\n    for batch in parquet.iter_batches(\n        batch_size=750_000,\n        columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\", \"played_ratio_pct\"],\n    ):\n        frame = batch.to_pandas()\n        mapped = item_index.get_indexer(frame.item_id.to_numpy(dtype=np.int64))\n        keep = mapped >= 0\n        if not np.any(keep):\n            continue\n        uids = frame.uid.to_numpy(dtype=np.int64, copy=False)[keep]\n        timestamps = frame.timestamp.to_numpy(dtype=np.int64, copy=False)[keep]\n        items = mapped[keep].astype(np.int32, copy=False)\n        organic = frame.is_organic.to_numpy(dtype=np.uint8, copy=False)[keep]\n        completion = frame.played_ratio_pct.to_numpy(dtype=np.uint16, copy=False)[keep]\n        if np.any(uids[1:] < uids[:-1]):\n            raise RuntimeError(f\"{path.name} is not sorted by uid\")\n        boundaries = np.r_[\n            0,\n            np.flatnonzero(uids[1:] != uids[:-1]) + 1,\n            len(uids),\n        ]\n        for start, end in zip(boundaries[:-1], boundaries[1:]):\n            uid = int(uids[start])\n            part = ListenEvents(\n                timestamps[start:end].copy(),\n                items[start:end].copy(),\n                organic[start:end].copy(),\n                completion[start:end].copy(),\n            )\n            if pending_uid is None:\n                pending_uid = uid\n            elif uid != pending_uid:\n                if pending_uid < previous_uid:\n                    raise RuntimeError(f\"{path.name} user order regressed\")\n                yield pending_uid, _combine_listen_chunks(pending)\n                previous_uid = pending_uid\n                pending_uid = uid\n                pending = []\n            pending.append(part)\n    if pending_uid is not None:\n        yield pending_uid, _combine_listen_chunks(pending)\n\n\ndef merge_listen_streams(\n    paths: list[Path], item_index: pd.Index\n) -> Iterator[tuple[int, ListenEvents]]:\n    \"\"\"Merge uid-sorted public listen files without materializing them.\"\"\"\n    streams = [iter(iter_listen_users(path, item_index)) for path in paths]\n    heads: list[tuple[int, ListenEvents] | None] = [\n        next(stream, None) for stream in streams\n    ]\n    while any(head is not None for head in heads):\n        uid = min(head[0] for head in heads if head is not None)\n        parts: list[ListenEvents] = []\n        for position, head in enumerate(heads):\n            if head is not None and head[0] == uid:\n                parts.append(head[1])\n                heads[position] = next(streams[position], None)\n        yield uid, _combine_listen_chunks(parts)\n\n\ndef load_explicit_events(\n    data: Path,\n    prefixes: tuple[str, ...],\n    item_index: pd.Index,\n) -> dict[int, ExplicitEvents]:\n    \"\"\"Load public explicit actions as chronological state changes.\"\"\"\n    specifications = (\n        (\"likes\", 0, 1, 0),\n        (\"unlikes\", 0, 0, 1),\n        (\"dislikes\", 1, 1, 0),\n        (\"undislikes\", 1, 0, 1),\n    )\n    parts: list[pd.DataFrame] = []\n    for family, channel, active, tie_priority in specifications:\n        for prefix in prefixes:\n            frame = pd.read_parquet(\n                data / f\"{prefix}_{family}.parquet\",\n                columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n            )\n            mapped = item_index.get_indexer(\n                frame.item_id.to_numpy(dtype=np.int64, copy=False)\n            )\n            keep = mapped >= 0\n            if not np.any(keep):\n                continue\n            retained = frame.loc[keep, [\"uid\", \"timestamp\", \"is_organic\"]].copy()\n            retained[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n            retained[\"channel\"] = np.int8(channel)\n            retained[\"active\"] = np.int8(active)\n            retained[\"tie_priority\"] = np.int8(tie_priority)\n            retained[\"organic_like\"] = np.int8(\n                family == \"likes\"\n            ) * retained.is_organic.astype(np.int8)\n            parts.append(retained.drop(columns=\"is_organic\"))\n    if not parts:\n        return {}\n    events = pd.concat(parts, ignore_index=True)\n    events = events.sort_values(\n        [\"uid\", \"timestamp\", \"tie_priority\"], kind=\"mergesort\"\n    ).reset_index(drop=True)\n    result: dict[int, ExplicitEvents] = {}\n    for uid, rows in events.groupby(\"uid\", sort=False):\n        result[int(uid)] = ExplicitEvents(\n            timestamps=rows.timestamp.to_numpy(dtype=np.int64, copy=True),\n            items=rows.item.to_numpy(dtype=np.int32, copy=True),\n            channel=rows.channel.to_numpy(dtype=np.int8, copy=True),\n            active=rows.active.to_numpy(dtype=np.int8, copy=True),\n            organic_like=rows.organic_like.to_numpy(dtype=np.int8, copy=True),\n        )\n    log(f\"loaded explicit events: rows={len(events):,} users={len(result):,}\")\n    return result\n\n\ndef empty_explicit_events() -> ExplicitEvents:\n    return ExplicitEvents(\n        timestamps=np.empty(0, dtype=np.int64),\n        items=np.empty(0, dtype=np.int32),\n        channel=np.empty(0, dtype=np.int8),\n        active=np.empty(0, dtype=np.int8),\n        organic_like=np.empty(0, dtype=np.int8),\n    )\n\n\ndef pack_active_items(\n    active: dict[int, int], width: int, padding_item: int\n) -> np.ndarray:\n    packed = np.full(width, padding_item, dtype=np.uint16)\n    if not active:\n        return packed\n    ordered = sorted(active.items(), key=lambda pair: (-pair[1], pair[0]))[:width]\n    packed[: len(ordered)] = np.fromiter(\n        (item for item, _ in ordered), dtype=np.uint16, count=len(ordered)\n    )\n    return packed\n\n\ndef load_inference_state(\n    path: Path,\n    item_index: pd.Index,\n    uids: np.ndarray,\n    n_items: int,\n) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:\n    \"\"\"Pack the task-provided active explicit state.\"\"\"\n    state = pd.read_parquet(path, columns=[\"uid\", \"item_id\", \"state\"])\n    mapped = item_index.get_indexer(state.item_id.to_numpy(dtype=np.int64))\n    keep = mapped >= 0\n    state = state.loc[keep, [\"uid\", \"state\"]].copy()\n    state[\"item\"] = mapped[keep].astype(np.int32, copy=False)\n    user_rows = pd.Index(uids)\n    liked = np.full((len(uids), LIKE_ITEMS), n_items, dtype=np.uint16)\n    disliked = np.full((len(uids), DISLIKE_ITEMS), n_items, dtype=np.uint16)\n    like_counts = np.zeros(len(uids), dtype=np.int32)\n    dislike_counts = np.zeros(len(uids), dtype=np.int32)\n    for value, width, destination, counts in (\n        (\"liked\", LIKE_ITEMS, liked, like_counts),\n        (\"disliked\", DISLIKE_ITEMS, disliked, dislike_counts),\n    ):\n        selected = state[state.state == value]\n        for uid, rows in selected.groupby(\"uid\", sort=False):\n            row = int(user_rows.get_indexer([int(uid)])[0])\n            if row < 0:\n                continue\n            items = np.sort(rows.item.unique())\n            counts[row] = len(items)\n            retained = items[:width]\n            destination[row, : len(retained)] = retained.astype(np.uint16)\n    return liked, disliked, like_counts, dislike_counts\n\n\nclass SequentialTwoTower(nn.Module):\n    \"\"\"Order-sensitive user tower and independent catalog-aware item tower.\"\"\"\n\n    def __init__(self, item_features: np.ndarray, config: TowerConfig) -> None:\n        super().__init__()\n        n_items, n_item_features = item_features.shape\n        dim = config.embedding_dim\n        self.n_items = n_items\n        self.context_embedding = nn.Embedding(\n            n_items + 1, dim, padding_idx=n_items\n        )\n        self.event_projection = nn.Sequential(\n            nn.Linear(dim + 3, config.hidden_dim),\n            nn.GELU(),\n        )\n        self.sequence_encoder = nn.GRU(\n            input_size=config.hidden_dim,\n            hidden_size=dim,\n            num_layers=1,\n            batch_first=True,\n        )\n        self.user_tower = nn.Sequential(\n            nn.Linear(dim * 3 + 6, config.user_hidden_1),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_1, config.user_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.user_hidden_2, dim),\n        )\n        self.candidate_embedding = nn.Embedding(n_items, dim)\n        self.register_buffer(\n            \"item_features\", torch.from_numpy(item_features), persistent=True\n        )\n        self.item_tower = nn.Sequential(\n            nn.Linear(dim + n_item_features, config.item_hidden_1),\n            nn.GELU(),\n"
            }
          }
        }
      ]
    },
    {
      "id": 8,
      "role": "agent",
      "timestamp": "2026-09-23T21:39:56.106Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:39:56.106Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:39:59.890Z",
          "callId": "call_WqCVZXekroCC6c4upEEiqZtP",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"rg -n \\\"negative|loss|sample|train_epoch|argparse|Config\\\\(|rank|submission|stage\\\" /app/solution/train_current_model.py /app/solution/two_tower_model.py && sed -n '320,760p' /app/solution/train_current_model.py && sed -n '320,620p' /app/solution/two_tower_model.py\",workdir:\"/app\",yield_time_ms:10000,max_output_tokens:40000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:39:59.947Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n/app/solution/two_tower_model.py:40:    uniform_negatives: int = 24\n/app/solution/two_tower_model.py:41:    inbatch_negatives: int = 8\n/app/solution/two_tower_model.py:73:    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n/app/solution/two_tower_model.py:79:            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n/app/solution/two_tower_model.py:346:def invalid_negative_mask(\n/app/solution/two_tower_model.py:347:    negatives: torch.Tensor,\n/app/solution/two_tower_model.py:353:    invalid = negatives.eq(targets[:, None])\n/app/solution/two_tower_model.py:354:    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:355:    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:356:    for column in range(1, negatives.shape[1]):\n/app/solution/two_tower_model.py:357:        invalid[:, column] |= negatives[:, column, None].eq(\n/app/solution/two_tower_model.py:358:            negatives[:, :column]\n/app/solution/two_tower_model.py:363:def draw_filtered_mixed_negatives(\n/app/solution/two_tower_model.py:374:    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n/app/solution/two_tower_model.py:406:    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n/app/solution/two_tower_model.py:407:    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n/app/solution/two_tower_model.py:412:    negatives = negatives_cpu.to(device)\n/app/solution/two_tower_model.py:415:        invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:416:            negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:419:            return negatives, correction\n/app/solution/two_tower_model.py:426:        negatives[invalid] = replacements\n/app/solution/two_tower_model.py:428:    invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:429:        negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:432:        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n/app/solution/two_tower_model.py:433:    return negatives, correction\n/app/solution/train_current_model.py:6:loss.  The fast default retains each user's most recent 128 training targets and\n/app/solution/train_current_model.py:9:computes all of its timestep losses and carries the detached GRU hidden state\n/app/solution/train_current_model.py:13:normalization, raw dot-product retrieval, sample-weighted binary cross entropy,\n/app/solution/train_current_model.py:14:and 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\n/app/solution/train_current_model.py:20:import argparse\n/app/solution/train_current_model.py:55:    loss_microbatch_size: int = 65_536\n/app/solution/train_current_model.py:56:    uniform_negatives: int = 24\n/app/solution/train_current_model.py:57:    inbatch_negatives: int = 8\n/app/solution/train_current_model.py:61:    negative_filter_scope: str = \"full-training-history\"\n/app/solution/train_current_model.py:152:    return base.TowerConfig(\n/app/solution/train_current_model.py:165:        uniform_negatives=config.uniform_negatives,\n/app/solution/train_current_model.py:166:        inbatch_negatives=config.inbatch_negatives,\n/app/solution/train_current_model.py:342:    public: Path, stage: str, config: Config\n/app/solution/train_current_model.py:346:        \"popularity_rank\"\n/app/solution/train_current_model.py:354:    if stage == \"validation\":\n/app/solution/train_current_model.py:463:        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:471:def cache_metadata(stage: str, config: Config) -> dict[str, object]:\n/app/solution/train_current_model.py:474:        \"stage\": stage,\n/app/solution/train_current_model.py:477:        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n/app/solution/train_current_model.py:482:    path: Path, prepared: SequenceData, stage: str, config: Config\n/app/solution/train_current_model.py:487:        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n/app/solution/train_current_model.py:493:def load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n/app/solution/train_current_model.py:496:        expected = cache_metadata(stage, config)\n/app/solution/train_current_model.py:513:    stage: str,\n/app/solution/train_current_model.py:519:        if stage == \"validation\"\n/app/solution/train_current_model.py:524:        prepared = load_cache(cache, stage, config)\n/app/solution/train_current_model.py:528:    prepared, built_eligibility = prepare_data(public, stage, config)\n/app/solution/train_current_model.py:530:        save_cache(cache, prepared, stage, config)\n/app/solution/train_current_model.py:603:        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:609:def invalid_full_history_negatives(\n/app/solution/train_current_model.py:610:    negatives: np.ndarray,\n/app/solution/train_current_model.py:616:    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n/app/solution/train_current_model.py:617:    byte_columns = negatives >> 3\n/app/solution/train_current_model.py:618:    bit_columns = negatives & 7\n/app/solution/train_current_model.py:621:    invalid |= negatives == targets[:, None]\n/app/solution/train_current_model.py:622:    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n/app/solution/train_current_model.py:623:    for column in range(1, negatives.shape[1]):\n/app/solution/train_current_model.py:625:            negatives[:, column, None] == negatives[:, :column]\n/app/solution/train_current_model.py:630:def draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:641:    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n/app/solution/train_current_model.py:647:        (batch_size, config.uniform_negatives),\n/app/solution/train_current_model.py:653:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:656:            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n/app/solution/train_current_model.py:672:        if corrected_count < config.inbatch_negatives:\n/app/solution/train_current_model.py:675:                (batch_size, config.inbatch_negatives - corrected_count),\n/app/solution/train_current_model.py:681:    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n/app/solution/train_current_model.py:682:    correction = np.ones_like(negatives, dtype=np.float32)\n/app/solution/train_current_model.py:685:            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n/app/solution/train_current_model.py:688:        invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:689:            negatives,\n/app/solution/train_current_model.py:697:                torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:706:        negatives[invalid] = replacements\n/app/solution/train_current_model.py:709:    invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:710:        negatives,\n/app/solution/train_current_model.py:717:        raise RuntimeError(\"full-history negative resampling failed\")\n/app/solution/train_current_model.py:719:        torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:724:def draw_training_negatives(\n/app/solution/train_current_model.py:736:    if config.negative_filter_scope == \"full-training-history\":\n/app/solution/train_current_model.py:738:            raise RuntimeError(\"full-history negative filter was not built\")\n/app/solution/train_current_model.py:739:        return draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:750:    return base.draw_filtered_mixed_negatives(\n/app/solution/train_current_model.py:755:        config.uniform_negatives,\n/app/solution/train_current_model.py:756:        config.inbatch_negatives,\n/app/solution/train_current_model.py:816:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:818:    all_items = torch.cat([positives, negatives.reshape(-1)])\n/app/solution/train_current_model.py:822:    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n/app/solution/train_current_model.py:823:        len(positives), negatives.shape[1], -1\n/app/solution/train_current_model.py:825:    return positive_vectors, negative_vectors\n/app/solution/train_current_model.py:845:def corrected_negative_loss(\n/app/solution/train_current_model.py:851:    total = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:853:    if config.uniform_negatives:\n/app/solution/train_current_model.py:854:        result += config.uniform_negatives * raw[\n/app/solution/train_current_model.py:855:            :, : config.uniform_negatives\n/app/solution/train_current_model.py:857:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:858:        selected = slice(config.uniform_negatives, total)\n/app/solution/train_current_model.py:860:        result += config.inbatch_negatives * (\n/app/solution/train_current_model.py:880:        raise RuntimeError(\"chronological target partition produced negative counts\")\n/app/solution/train_current_model.py:915:    public: Path, stage: str, item_ids: np.ndarray\n/app/solution/train_current_model.py:918:    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n/app/solution/train_current_model.py:957:    stage: str,\n/app/solution/train_current_model.py:978:                public, stage, prepared.item_ids\n/app/solution/train_current_model.py:981:                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n/app/solution/train_current_model.py:1119:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:1120:    negative_weights: torch.Tensor,\n/app/solution/train_current_model.py:1121:    sample_weights: np.ndarray,\n/app/solution/train_current_model.py:1127:    total_weight = float(sample_weights.sum())\n/app/solution/train_current_model.py:1129:        raise RuntimeError(\"target block has no positive sample weight\")\n/app/solution/train_current_model.py:1132:        \"loss_sum\": 0.0,\n/app/solution/train_current_model.py:1134:        \"negative_sum\": 0.0,\n/app/solution/train_current_model.py:1138:    for begin in range(0, target_count, config.loss_microbatch_size):\n/app/solution/train_current_model.py:1139:        end = min(begin + config.loss_microbatch_size, target_count)\n/app/solution/train_current_model.py:1162:        positive_vectors, negative_vectors = candidate_vectors(\n/app/solution/train_current_model.py:1165:            negatives[begin:end],\n/app/solution/train_current_model.py:1168:        negative_logits = torch.einsum(\n/app/solution/train_current_model.py:1169:            \"bd,bkd->bk\", query_vectors, negative_vectors\n/app/solution/train_current_model.py:1171:        positive_loss = F.softplus(-positive_logits)\n/app/solution/train_current_model.py:1172:        negative_loss = corrected_negative_loss(\n/app/solution/train_current_model.py:1173:            negative_logits, negative_weights[begin:end], config\n/app/solution/train_current_model.py:1176:            sample_weights[begin:end].astype(np.float32, copy=False)\n/app/solution/train_current_model.py:1178:        loss_sum = (\n/app/solution/train_current_model.py:1179:            selected_weights * (positive_loss + negative_loss) / 2.0\n/app/solution/train_current_model.py:1181:        if not bool(torch.isfinite(loss_sum)):\n/app/solution/train_current_model.py:1182:            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n/app/solution/train_current_model.py:1184:            (loss_sum / total_weight).backward()\n/app/solution/train_current_model.py:1188:        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n/app/solution/train_current_model.py:1190:        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n/app/solution/train_current_model.py:1192:            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n/app/solution/train_current_model.py:1227:    negative_count = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:1228:    total_loss = 0.0\n/app/solution/train_current_model.py:1232:    total_negative = 0.0\n/app/solution/train_current_model.py:1293:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1314:                negatives,\n/app/solution/train_current_model.py:1315:                negative_weights,\n/app/solution/train_current_model.py:1327:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1331:            total_negative += statistics[\"negative_sum\"]\n/app/solution/train_current_model.py:1337:                batch_bce = statistics[\"loss_sum\"] / max(\n/app/solution/train_current_model.py:1340:                running_bce = total_loss / max(total_weight, 1.0e-12)\n/app/solution/train_current_model.py:1351:        \"loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1353:        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1355:        / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1388:    total_loss = 0.0\n/app/solution/train_current_model.py:1449:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1469:                negatives,\n/app/solution/train_current_model.py:1470:                negative_weights,\n/app/solution/train_current_model.py:1475:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1481:        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1523:    stage: str,\n/app/solution/train_current_model.py:1560:        stage,\n/app/solution/train_current_model.py:1567:        if config.negative_filter_scope == \"full-training-history\"\n/app/solution/train_current_model.py:1571:    best_loss = float(\"inf\")\n/app/solution/train_current_model.py:1601:            \"negative_filter_scope\", \"last-100\"\n/app/solution/train_current_model.py:1629:            stored_filter_scope != config.negative_filter_scope\n/app/solution/train_current_model.py:1657:            prior.pop(\"validation_loss\", None)\n/app/solution/train_current_model.py:1660:                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n/app/solution/train_current_model.py:1666:        if \"validation_loss\" not in prior:\n/app/solution/train_current_model.py:1682:        best_loss = float(prior[\"validation_loss\"])\n/app/solution/train_current_model.py:1687:            f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1731:            diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1732:            < best_loss - config.early_stopping_min_delta\n/app/solution/train_current_model.py:1735:            best_loss = diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1754:            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n/app/solution/train_current_model.py:1755:            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n/app/solution/train_current_model.py:1766:                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1776:        f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1861:def rank_candidates(\n/app/solution/train_current_model.py:1867:    ranking_batch_size: int,\n/app/solution/train_current_model.py:1882:    for start in range(0, len(eligibility.uids), ranking_batch_size):\n/app/solution/train_current_model.py:1883:        end = min(start + ranking_batch_size, len(eligibility.uids))\n/app/solution/train_current_model.py:1896:                (uid, int(prepared.item_ids[column]), rank)\n/app/solution/train_current_model.py:1897:                for rank, column in enumerate(columns, start=1)\n/app/solution/train_current_model.py:1900:            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n/app/solution/train_current_model.py:1909:    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n/app/solution/train_current_model.py:1912:def write_ranking(frame: pd.DataFrame, output: Path) -> None:\n/app/solution/train_current_model.py:1923:    parser = argparse.ArgumentParser(description=__doc__)\n/app/solution/train_current_model.py:1925:        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n/app/solution/train_current_model.py:1939:        \"--loss-microbatch-size\",\n/app/solution/train_current_model.py:1941:        default=Config.loss_microbatch_size,\n/app/solution/train_current_model.py:1944:        \"--negative-filter-scope\",\n/app/solution/train_current_model.py:1946:        default=Config.negative_filter_scope,\n/app/solution/train_current_model.py:2003:    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n/app/solution/train_current_model.py:2012:        or args.loss_microbatch_size < 1\n/app/solution/train_current_model.py:2028:    config = Config(\n/app/solution/train_current_model.py:2033:        loss_microbatch_size=args.loss_microbatch_size,\n/app/solution/train_current_model.py:2034:        negative_filter_scope=args.negative_filter_scope,\n/app/solution/train_current_model.py:2057:        args.stage,\n/app/solution/train_current_model.py:2071:                    \"stage\": args.stage,\n/app/solution/train_current_model.py:2095:        args.stage,\n/app/solution/train_current_model.py:2102:    ranking, embedding_diagnostics = rank_candidates(\n/app/solution/train_current_model.py:2108:        args.ranking_batch_size,\n/app/solution/train_current_model.py:2110:    write_ranking(ranking, args.output.resolve())\n/app/solution/train_current_model.py:2115:                \"stage\": args.stage,\n/app/solution/train_current_model.py:2117:                \"rows\": len(ranking),\n/app/solution/train_current_model.py:2118:                \"users\": int(ranking.uid.nunique()),\n/app/solution/train_current_model.py:2126:                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n/app/solution/train_current_model.py:2129:                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n/app/solution/train_current_model.py:2135:                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n/app/solution/train_current_model.py:2136:                    \"negative_sampling\": (\n/app/solution/train_current_model.py:2139:                    \"false_negative_filter\": config.negative_filter_scope,\n    dislike_count: int,\n) -> np.ndarray:\n    start = int(\n        np.searchsorted(\n            timestamps,\n            history_end - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n            side=\"left\",\n        )\n    )\n    result = np.zeros(6, dtype=np.float32)\n    recent_items = items[start:]\n    if len(recent_items):\n        result[0] = np.log1p(len(recent_items)) / 8.0\n        result[1] = np.log1p(len(np.unique(recent_items))) / 6.0\n        result[2] = float(np.mean(event_features[start:, 0]))\n        result[3] = float(np.mean(event_features[start:, 1]))\n    result[4] = np.log1p(like_count) / 6.0\n    result[5] = np.log1p(dislike_count) / 4.0\n    return result\n\n\ndef prepare_data(\n    public: Path, stage: str, config: Config\n) -> tuple[SequenceData, CandidateSet]:\n    data = public / \"data\"\n    catalog = pd.read_parquet(data / \"candidate_catalog.parquet\").sort_values(\n        \"popularity_rank\"\n    )\n    item_ids = catalog.item_id.to_numpy(dtype=np.int64, copy=True)\n    item_index = pd.Index(item_ids)\n    n_items = len(item_ids)\n    if n_items >= np.iinfo(np.uint16).max:\n        raise RuntimeError(\"uint16 item storage is too small for this catalog\")\n\n    if stage == \"validation\":\n        prefixes = (\"train\",)\n        history_end = base.TRAIN_END\n        candidate_name = \"validation_eligible_candidates.npz\"\n        state_name = \"validation_preference_state.parquet\"\n    else:\n        prefixes = (\"train\", \"val\")\n        history_end = base.VALIDATION_END\n        candidate_name = \"test_eligible_candidates.npz\"\n        state_name = \"test_preference_state.parquet\"\n    eligibility = CandidateSet.read(data / candidate_name)\n    if not np.array_equal(eligibility.item_ids, item_ids):\n        raise RuntimeError(\"catalog and candidate artifact item order differ\")\n\n    explicit_by_user = base.load_explicit_events(data, prefixes, item_index)\n    inference_likes, inference_dislikes, like_counts, dislike_counts = (\n        base.load_inference_state(\n            data / state_name,\n            item_index,\n            eligibility.uids,\n            n_items,\n        )\n    )\n    inference_rows = {int(uid): row for row, uid in enumerate(eligibility.uids)}\n    inference_user_features = np.zeros((len(eligibility.uids), 6), dtype=np.float32)\n    inference_sequence_rows = np.full(len(eligibility.uids), -1, dtype=np.int32)\n\n    # Snapshot zero is the shared empty explicit state.\n    liked_states = [np.full(base.LIKE_ITEMS, n_items, dtype=np.uint16)]\n    disliked_states = [\n        np.full(base.DISLIKE_ITEMS, n_items, dtype=np.uint16)\n    ]\n    state_counts: list[tuple[int, int]] = [(0, 0)]\n    user_ids: list[int] = []\n    offsets = [0]\n    timestamp_parts: list[np.ndarray] = []\n    item_parts: list[np.ndarray] = []\n    event_parts: list[np.ndarray] = []\n    activity_parts: list[np.ndarray] = []\n    state_parts: list[np.ndarray] = []\n\n    listen_paths = [data / f\"{prefix}_listens.parquet\" for prefix in prefixes]\n    started = time.monotonic()\n    for seen_users, (uid, listens) in enumerate(\n        base.merge_listen_streams(listen_paths, item_index), start=1\n    ):\n        parts = build_sequence_parts(\n            listens,\n            explicit_by_user.get(uid, base.empty_explicit_events()),\n            n_items,\n            liked_states,\n            disliked_states,\n            state_counts,\n        )\n        if parts is None:\n            continue\n        sequence_row = len(user_ids)\n        user_ids.append(uid)\n        timestamp_parts.append(parts[0].astype(np.uint32, copy=False))\n        item_parts.append(parts[1])\n        event_parts.append(parts[2])\n        activity_parts.append(parts[3])\n        state_parts.append(parts[4])\n        offsets.append(offsets[-1] + len(parts[1]))\n        inference_row = inference_rows.get(uid)\n        if inference_row is not None:\n            inference_sequence_rows[inference_row] = sequence_row\n            inference_user_features[inference_row] = final_user_features(\n                parts[0],\n                parts[1],\n                parts[2],\n                history_end,\n                int(like_counts[inference_row]),\n                int(dislike_counts[inference_row]),\n            )\n        if seen_users % 1_000 == 0:\n            log(\n                f\"prepared users={seen_users:,} tokens={offsets[-1]:,} \"\n                f\"states={len(liked_states):,} \"\n                f\"elapsed={time.monotonic() - started:.1f}s\"\n            )\n\n    missing = np.flatnonzero(inference_sequence_rows < 0)\n    if len(missing):\n        inference_user_features[missing, 4] = np.log1p(like_counts[missing]) / 6.0\n        inference_user_features[missing, 5] = (\n            np.log1p(dislike_counts[missing]) / 4.0\n        )\n        log(f\"target users without qualifying catalog sequence={len(missing):,}\")\n\n    prepared = SequenceData(\n        item_ids=item_ids,\n        item_features=base.build_item_features(catalog),\n        user_ids=np.asarray(user_ids, dtype=np.int64),\n        offsets=np.asarray(offsets, dtype=np.int64),\n        sequence_timestamps=np.concatenate(timestamp_parts),\n        sequence_items=np.concatenate(item_parts),\n        event_features=np.concatenate(event_parts),\n        activity_features=np.concatenate(activity_parts),\n        state_ids=np.concatenate(state_parts),\n        liked_states=np.stack(liked_states),\n        disliked_states=np.stack(disliked_states),\n        state_counts=np.asarray(state_counts, dtype=np.int32),\n        inference_user_rows=inference_sequence_rows,\n        inference_liked_items=inference_likes,\n        inference_disliked_items=inference_dislikes,\n        inference_user_features=inference_user_features,\n    )\n    log(\n        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n        f\"tokens={len(prepared.sequence_items):,} \"\n        f\"next_item_targets={prepared.target_count:,} \"\n        f\"states={len(prepared.liked_states):,}\"\n    )\n    return prepared, eligibility\n\n\ndef cache_metadata(stage: str, config: Config) -> dict[str, object]:\n    return {\n        \"cache_version\": CACHE_VERSION,\n        \"stage\": stage,\n        \"positive_listen_threshold\": base.LISTEN_POSITIVE_THRESHOLD,\n        \"profile_lookback_days\": base.PROFILE_LOOKBACK_DAYS,\n        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n    }\n\n\ndef save_cache(\n    path: Path, prepared: SequenceData, stage: str, config: Config\n) -> None:\n    path.parent.mkdir(parents=True, exist_ok=True)\n    np.savez(\n        path,\n        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n        **prepared.__dict__,\n    )\n    log(f\"saved public-derived full-sequence cache: {path}\")\n\n\ndef load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n    with np.load(path, allow_pickle=False) as artifact:\n        actual = json.loads(str(artifact[\"metadata\"].item()))\n        expected = cache_metadata(stage, config)\n        if actual != expected:\n            raise RuntimeError(f\"sequence cache differs: {actual} != {expected}\")\n        values = {\n            field: artifact[field].copy()\n            for field in SequenceData.__dataclass_fields__\n        }\n    prepared = SequenceData(**values)\n    log(\n        f\"loaded full-sequence cache: tokens={len(prepared.sequence_items):,} \"\n        f\"targets={prepared.target_count:,}\"\n    )\n    return prepared\n\n\ndef load_or_prepare(\n    public: Path,\n    stage: str,\n    config: Config,\n    cache: Path | None,\n) -> tuple[SequenceData, CandidateSet]:\n    candidate_name = (\n        \"validation_eligible_candidates.npz\"\n        if stage == \"validation\"\n        else \"test_eligible_candidates.npz\"\n    )\n    eligibility = CandidateSet.read(public / \"data\" / candidate_name)\n    if cache is not None and cache.is_file():\n        prepared = load_cache(cache, stage, config)\n        if not np.array_equal(prepared.item_ids, eligibility.item_ids):\n            raise RuntimeError(\"cached catalog differs from candidate artifact\")\n        return prepared, eligibility\n    prepared, built_eligibility = prepare_data(public, stage, config)\n    if cache is not None:\n        save_cache(cache, prepared, stage, config)\n    return prepared, built_eligibility\n\n\ndef build_item_correction(\n    prepared: SequenceData,\n    config: Config,\n    target_starts: np.ndarray,\n    target_counts: np.ndarray,\n) -> torch.Tensor:\n    \"\"\"Estimate in-batch propensities from the selected training targets.\"\"\"\n    counts = np.zeros(len(prepared.item_ids), dtype=np.float64)\n    for user_row, count in enumerate(target_counts):\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        target_start = int(target_starts[user_row])\n        counts += np.bincount(\n            prepared.sequence_items[\n                offset\n                + target_start\n                + 1 : offset\n                + target_start\n                + int(count)\n                + 1\n            ].astype(np.int64),\n            minlength=len(prepared.item_ids),\n        )\n    total = float(counts.sum())\n    probabilities = (counts + 1.0) / (total + len(counts))\n    raw = np.power(\n        (1.0 / len(counts)) / probabilities,\n        config.inbatch_correction_power,\n    )\n    normalization = float(np.sum(counts * raw) / max(total, 1.0))\n    correction = np.clip(\n        raw / max(normalization, 1.0e-12),\n        config.inbatch_correction_min,\n        config.inbatch_correction_max,\n    ).astype(np.float32)\n    mean_on_targets = float(np.sum(counts * correction) / max(total, 1.0))\n    log(\n        f\"inbatch correction: min={correction.min():.3f} \"\n        f\"mean_on_targets={mean_on_targets:.3f} max={correction.max():.3f}\"\n    )\n    return torch.from_numpy(correction)\n\n\ndef build_known_positive_filter(\n    prepared: SequenceData, training_counts: np.ndarray\n) -> np.ndarray:\n    \"\"\"Pack each user's complete public-training positive-item set.\"\"\"\n    width = (len(prepared.item_ids) + 7) // 8\n    packed = np.zeros((len(prepared.user_ids), width), dtype=np.uint8)\n    retained = 0\n    for user_row, target_count in enumerate(training_counts):\n        if not target_count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        # T adjacent targets consume sequence positions 0 through T.  The\n        # chronological BCE suffix starts at T + 1 and is intentionally absent.\n        items = np.unique(\n            prepared.sequence_items[\n                offset : offset + int(target_count) + 1\n            ].astype(np.int64)\n        )\n        byte_columns = items >> 3\n        bit_values = np.left_shift(\n            np.uint8(1), (items & 7).astype(np.uint8)\n        )\n        np.bitwise_or.at(packed[user_row], byte_columns, bit_values)\n        retained += len(items)\n    log(\n        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n        f\"unique_user_items={retained:,} bytes={packed.nbytes:,}\"\n    )\n    return packed\n\n\ndef invalid_full_history_negatives(\n    negatives: np.ndarray,\n    targets: np.ndarray,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray,\n    liked_items: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n    byte_columns = negatives >> 3\n    bit_columns = negatives & 7\n    known = known_positive_packed[user_rows[:, None], byte_columns]\n    invalid = ((known >> bit_columns) & 1).astype(bool)\n    invalid |= negatives == targets[:, None]\n    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= (\n            negatives[:, column, None] == negatives[:, :column]\n        ).any(axis=1)\n    return invalid\n\n\ndef draw_full_history_filtered_negatives(\n    targets: torch.Tensor,\n    user_rows: np.ndarray,\n    liked_items: torch.Tensor,\n    known_positive_packed: np.ndarray,\n    n_items: int,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n    targets_cpu = targets.detach().cpu().numpy().astype(np.int64, copy=False)\n    liked_cpu = liked_items.detach().cpu().numpy().astype(np.int64, copy=False)\n    batch_size = len(targets_cpu)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, config.uniform_negatives),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n    corrected_count = 0\n    if config.inbatch_negatives:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(\n            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n        )\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(\n                    torch.from_numpy(targets_cpu)[:, None]\n                ),\n                -1.0,\n            )\n            columns = torch.topk(\n                priorities, k=corrected_count, dim=1\n            ).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < config.inbatch_negatives:\n            filler = torch.randint(\n                n_items,\n                (batch_size, config.inbatch_negatives - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n    correction = np.ones_like(negatives, dtype=np.float32)\n    if corrected_count:\n        correction[\n            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]].numpy()\n    for _ in range(32):\n        invalid = invalid_full_history_negatives(\n            negatives,\n            targets_cpu,\n            user_rows,\n            known_positive_packed,\n            liked_cpu,\n        )\n        if not np.any(invalid):\n            return (\n                torch.from_numpy(negatives).to(device),\n                torch.from_numpy(correction).to(device),\n            )\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum()),),\n            generator=generator,\n            device=\"cpu\",\n        ).numpy()\n        negatives[invalid] = replacements\n        # Rejected in-batch items become ordinary uniform draws.\n        correction[invalid] = 1.0\n    invalid = invalid_full_history_negatives(\n        negatives,\n        targets_cpu,\n        user_rows,\n        known_positive_packed,\n        liked_cpu,\n    )\n    if np.any(invalid):\n        raise RuntimeError(\"full-history negative resampling failed\")\n    return (\n        torch.from_numpy(negatives).to(device),\n        torch.from_numpy(correction).to(device),\n    )\n\n\ndef draw_training_negatives(\n    positive_items: torch.Tensor,\n    known_history: torch.Tensor,\n    liked_items: torch.Tensor,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray | None,\n    prepared: SequenceData,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    if config.negative_filter_scope == \"full-training-history\":\n        if known_positive_packed is None:\n            raise RuntimeError(\"full-history negative filter was not built\")\n        return draw_full_history_filtered_negatives(\n            positive_items,\n            user_rows,\n            liked_items,\n            known_positive_packed,\n            len(prepared.item_ids),\n            config,\n            item_correction,\n            generator,\n            device,\n        )\n    return base.draw_filtered_mixed_negatives(\n        positive_items,\n        known_history,\n        liked_items,\n        len(prepared.item_ids),\n        config.uniform_negatives,\n        config.inbatch_negatives,\n        item_correction,\n        generator,\n        device,\n    )\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_1, config.item_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_2, dim),\n        )\n        nn.init.normal_(self.context_embedding.weight, std=0.02)\n        nn.init.normal_(self.candidate_embedding.weight, std=0.02)\n        with torch.no_grad():\n            self.context_embedding.weight[n_items].zero_()\n\n    def _mean_context_channel(self, items: torch.Tensor) -> torch.Tensor:\n        mask = items.ne(self.n_items)\n        vectors = self.context_embedding(items)\n        return (vectors * mask.unsqueeze(-1)).sum(dim=1) / mask.sum(\n            dim=1, keepdim=True\n        ).clamp_min(1)\n\n    def encode_items(self, items: torch.Tensor) -> torch.Tensor:\n        inputs = torch.cat(\n            [self.candidate_embedding(items), self.item_features[items]], dim=1\n        )\n        return self.item_tower(inputs)\n\n\ndef invalid_negative_mask(\n    negatives: torch.Tensor,\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n) -> torch.Tensor:\n    \"\"\"Identify targets, known positives, active likes, and row duplicates.\"\"\"\n    invalid = negatives.eq(targets[:, None])\n    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= negatives[:, column, None].eq(\n            negatives[:, :column]\n        ).any(dim=1)\n    return invalid\n\n\ndef draw_filtered_mixed_negatives(\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n    n_items: int,\n    uniform_count: int,\n    inbatch_count: int,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n    batch_size = len(targets)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, uniform_count),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long, device=\"cpu\")\n    corrected_count = 0\n    if inbatch_count:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(inbatch_count, max(len(unique_targets) - 1, 0))\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(targets.detach().cpu()[:, None]),\n                -1.0,\n            )\n            columns = torch.topk(priorities, k=corrected_count, dim=1).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < inbatch_count:\n            filler = torch.randint(\n                n_items,\n                (batch_size, inbatch_count - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n    if corrected_count:\n        correction_cpu[\n            :, uniform_count : uniform_count + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]]\n    negatives = negatives_cpu.to(device)\n    correction = correction_cpu.to(device)\n    for _ in range(32):\n        invalid = invalid_negative_mask(\n            negatives, targets, context_items, liked_items\n        )\n        if not bool(invalid.any()):\n            return negatives, correction\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum().detach().cpu()),),\n            generator=generator,\n            device=\"cpu\",\n        ).to(device)\n        negatives[invalid] = replacements\n        correction[invalid] = 1.0\n    invalid = invalid_negative_mask(\n        negatives, targets, context_items, liked_items\n    )\n    if bool(invalid.any()):\n        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n    return negatives, correction\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:39:59.934Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-a8e27413-3e80-4678-9165-014ea2eb65be",
              "process_id": "36446",
              "command": [
                "/bin/sh",
                "-lc",
                "rg -n \"negative|loss|sample|train_epoch|argparse|Config\\(|rank|submission|stage\" /app/solution/train_current_model.py /app/solution/two_tower_model.py && sed -n '320,760p' /app/solution/train_current_model.py && sed -n '320,620p' /app/solution/two_tower_model.py"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "search",
                  "cmd": "rg -n \"negative|loss|sample|train_epoch|argparse|Config\\\\(|rank|submission|stage\" /app/solution/train_current_model.py /app/solution/two_tower_model.py",
                  "query": "negative|loss|sample|train_epoch|argparse|Config\\(|rank|submission|stage",
                  "path": "train_current_model.py"
                },
                {
                  "type": "read",
                  "cmd": "sed -n '320,760p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                },
                {
                  "type": "read",
                  "cmd": "sed -n '320,620p' /app/solution/two_tower_model.py",
                  "name": "two_tower_model.py",
                  "path": "/app/solution/two_tower_model.py"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "/app/solution/two_tower_model.py:40:    uniform_negatives: int = 24\n/app/solution/two_tower_model.py:41:    inbatch_negatives: int = 8\n/app/solution/two_tower_model.py:73:    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n/app/solution/two_tower_model.py:79:            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n/app/solution/two_tower_model.py:346:def invalid_negative_mask(\n/app/solution/two_tower_model.py:347:    negatives: torch.Tensor,\n/app/solution/two_tower_model.py:353:    invalid = negatives.eq(targets[:, None])\n/app/solution/two_tower_model.py:354:    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:355:    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:356:    for column in range(1, negatives.shape[1]):\n/app/solution/two_tower_model.py:357:        invalid[:, column] |= negatives[:, column, None].eq(\n/app/solution/two_tower_model.py:358:            negatives[:, :column]\n/app/solution/two_tower_model.py:363:def draw_filtered_mixed_negatives(\n/app/solution/two_tower_model.py:374:    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n/app/solution/two_tower_model.py:406:    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n/app/solution/two_tower_model.py:407:    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n/app/solution/two_tower_model.py:412:    negatives = negatives_cpu.to(device)\n/app/solution/two_tower_model.py:415:        invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:416:            negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:419:            return negatives, correction\n/app/solution/two_tower_model.py:426:        negatives[invalid] = replacements\n/app/solution/two_tower_model.py:428:    invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:429:        negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:432:        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n/app/solution/two_tower_model.py:433:    return negatives, correction\n/app/solution/train_current_model.py:6:loss.  The fast default retains each user's most recent 128 training targets and\n/app/solution/train_current_model.py:9:computes all of its timestep losses and carries the detached GRU hidden state\n/app/solution/train_current_model.py:13:normalization, raw dot-product retrieval, sample-weighted binary cross entropy,\n/app/solution/train_current_model.py:14:and 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\n/app/solution/train_current_model.py:20:import argparse\n/app/solution/train_current_model.py:55:    loss_microbatch_size: int = 65_536\n/app/solution/train_current_model.py:56:    uniform_negatives: int = 24\n/app/solution/train_current_model.py:57:    inbatch_negatives: int = 8\n/app/solution/train_current_model.py:61:    negative_filter_scope: str = \"full-training-history\"\n/app/solution/train_current_model.py:152:    return base.TowerConfig(\n/app/solution/train_current_model.py:165:        uniform_negatives=config.uniform_negatives,\n/app/solution/train_current_model.py:166:        inbatch_negatives=config.inbatch_negatives,\n/app/solution/train_current_model.py:342:    public: Path, stage: str, config: Config\n/app/solution/train_current_model.py:346:        \"popularity_rank\"\n/app/solution/train_current_model.py:354:    if stage == \"validation\":\n/app/solution/train_current_model.py:463:        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:471:def cache_metadata(stage: str, config: Config) -> dict[str, object]:\n/app/solution/train_current_model.py:474:        \"stage\": stage,\n/app/solution/train_current_model.py:477:        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n/app/solution/train_current_model.py:482:    path: Path, prepared: SequenceData, stage: str, config: Config\n/app/solution/train_current_model.py:487:        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n/app/solution/train_current_model.py:493:def load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n/app/solution/train_current_model.py:496:        expected = cache_metadata(stage, config)\n/app/solution/train_current_model.py:513:    stage: str,\n/app/solution/train_current_model.py:519:        if stage == \"validation\"\n/app/solution/train_current_model.py:524:        prepared = load_cache(cache, stage, config)\n/app/solution/train_current_model.py:528:    prepared, built_eligibility = prepare_data(public, stage, config)\n/app/solution/train_current_model.py:530:        save_cache(cache, prepared, stage, config)\n/app/solution/train_current_model.py:603:        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:609:def invalid_full_history_negatives(\n/app/solution/train_current_model.py:610:    negatives: np.ndarray,\n/app/solution/train_current_model.py:616:    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n/app/solution/train_current_model.py:617:    byte_columns = negatives >> 3\n/app/solution/train_current_model.py:618:    bit_columns = negatives & 7\n/app/solution/train_current_model.py:621:    invalid |= negatives == targets[:, None]\n/app/solution/train_current_model.py:622:    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n/app/solution/train_current_model.py:623:    for column in range(1, negatives.shape[1]):\n/app/solution/train_current_model.py:625:            negatives[:, column, None] == negatives[:, :column]\n/app/solution/train_current_model.py:630:def draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:641:    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n/app/solution/train_current_model.py:647:        (batch_size, config.uniform_negatives),\n/app/solution/train_current_model.py:653:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:656:            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n/app/solution/train_current_model.py:672:        if corrected_count < config.inbatch_negatives:\n/app/solution/train_current_model.py:675:                (batch_size, config.inbatch_negatives - corrected_count),\n/app/solution/train_current_model.py:681:    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n/app/solution/train_current_model.py:682:    correction = np.ones_like(negatives, dtype=np.float32)\n/app/solution/train_current_model.py:685:            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n/app/solution/train_current_model.py:688:        invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:689:            negatives,\n/app/solution/train_current_model.py:697:                torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:706:        negatives[invalid] = replacements\n/app/solution/train_current_model.py:709:    invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:710:        negatives,\n/app/solution/train_current_model.py:717:        raise RuntimeError(\"full-history negative resampling failed\")\n/app/solution/train_current_model.py:719:        torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:724:def draw_training_negatives(\n/app/solution/train_current_model.py:736:    if config.negative_filter_scope == \"full-training-history\":\n/app/solution/train_current_model.py:738:            raise RuntimeError(\"full-history negative filter was not built\")\n/app/solution/train_current_model.py:739:        return draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:750:    return base.draw_filtered_mixed_negatives(\n/app/solution/train_current_model.py:755:        config.uniform_negatives,\n/app/solution/train_current_model.py:756:        config.inbatch_negatives,\n/app/solution/train_current_model.py:816:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:818:    all_items = torch.cat([positives, negatives.reshape(-1)])\n/app/solution/train_current_model.py:822:    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n/app/solution/train_current_model.py:823:        len(positives), negatives.shape[1], -1\n/app/solution/train_current_model.py:825:    return positive_vectors, negative_vectors\n/app/solution/train_current_model.py:845:def corrected_negative_loss(\n/app/solution/train_current_model.py:851:    total = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:853:    if config.uniform_negatives:\n/app/solution/train_current_model.py:854:        result += config.uniform_negatives * raw[\n/app/solution/train_current_model.py:855:            :, : config.uniform_negatives\n/app/solution/train_current_model.py:857:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:858:        selected = slice(config.uniform_negatives, total)\n/app/solution/train_current_model.py:860:        result += config.inbatch_negatives * (\n/app/solution/train_current_model.py:880:        raise RuntimeError(\"chronological target partition produced negative counts\")\n/app/solution/train_current_model.py:915:    public: Path, stage: str, item_ids: np.ndarray\n/app/solution/train_current_model.py:918:    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n/app/solution/train_current_model.py:957:    stage: str,\n/app/solution/train_current_model.py:978:                public, stage, prepared.item_ids\n/app/solution/train_current_model.py:981:                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n/app/solution/train_current_model.py:1119:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:1120:    negative_weights: torch.Tensor,\n/app/solution/train_current_model.py:1121:    sample_weights: np.ndarray,\n/app/solution/train_current_model.py:1127:    total_weight = float(sample_weights.sum())\n/app/solution/train_current_model.py:1129:        raise RuntimeError(\"target block has no positive sample weight\")\n/app/solution/train_current_model.py:1132:        \"loss_sum\": 0.0,\n/app/solution/train_current_model.py:1134:        \"negative_sum\": 0.0,\n/app/solution/train_current_model.py:1138:    for begin in range(0, target_count, config.loss_microbatch_size):\n/app/solution/train_current_model.py:1139:        end = min(begin + config.loss_microbatch_size, target_count)\n/app/solution/train_current_model.py:1162:        positive_vectors, negative_vectors = candidate_vectors(\n/app/solution/train_current_model.py:1165:            negatives[begin:end],\n/app/solution/train_current_model.py:1168:        negative_logits = torch.einsum(\n/app/solution/train_current_model.py:1169:            \"bd,bkd->bk\", query_vectors, negative_vectors\n/app/solution/train_current_model.py:1171:        positive_loss = F.softplus(-positive_logits)\n/app/solution/train_current_model.py:1172:        negative_loss = corrected_negative_loss(\n/app/solution/train_current_model.py:1173:            negative_logits, negative_weights[begin:end], config\n/app/solution/train_current_model.py:1176:            sample_weights[begin:end].astype(np.float32, copy=False)\n/app/solution/train_current_model.py:1178:        loss_sum = (\n/app/solution/train_current_model.py:1179:            selected_weights * (positive_loss + negative_loss) / 2.0\n/app/solution/train_current_model.py:1181:        if not bool(torch.isfinite(loss_sum)):\n/app/solution/train_current_model.py:1182:            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n/app/solution/train_current_model.py:1184:            (loss_sum / total_weight).backward()\n/app/solution/train_current_model.py:1188:        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n/app/solution/train_current_model.py:1190:        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n/app/solution/train_current_model.py:1192:            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n/app/solution/train_current_model.py:1227:    negative_count = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:1228:    total_loss = 0.0\n/app/solution/train_current_model.py:1232:    total_negative = 0.0\n/app/solution/train_current_model.py:1293:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1314:                negatives,\n/app/solution/train_current_model.py:1315:                negative_weights,\n/app/solution/train_current_model.py:1327:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1331:            total_negative += statistics[\"negative_sum\"]\n/app/solution/train_current_model.py:1337:                batch_bce = statistics[\"loss_sum\"] / max(\n/app/solution/train_current_model.py:1340:                running_bce = total_loss / max(total_weight, 1.0e-12)\n/app/solution/train_current_model.py:1351:        \"loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1353:        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1355:        / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1388:    total_loss = 0.0\n/app/solution/train_current_model.py:1449:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1469:                negatives,\n/app/solution/train_current_model.py:1470:                negative_weights,\n/app/solution/train_current_model.py:1475:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1481:        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1523:    stage: str,\n/app/solution/train_current_model.py:1560:        stage,\n/app/solution/train_current_model.py:1567:        if config.negative_filter_scope == \"full-training-history\"\n/app/solution/train_current_model.py:1571:    best_loss = float(\"inf\")\n/app/solution/train_current_model.py:1601:            \"negative_filter_scope\", \"last-100\"\n/app/solution/train_current_model.py:1629:            stored_filter_scope != config.negative_filter_scope\n/app/solution/train_current_model.py:1657:            prior.pop(\"validation_loss\", None)\n/app/solution/train_current_model.py:1660:                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n/app/solution/train_current_model.py:1666:        if \"validation_loss\" not in prior:\n/app/solution/train_current_model.py:1682:        best_loss = float(prior[\"validation_loss\"])\n/app/solution/train_current_model.py:1687:            f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1731:            diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1732:            < best_loss - config.early_stopping_min_delta\n/app/solution/train_current_model.py:1735:            best_loss = diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1754:            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n/app/solution/train_current_model.py:1755:            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n/app/solution/train_current_model.py:1766:                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1776:        f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1861:def rank_candidates(\n/app/solution/train_current_model.py:1867:    ranking_batch_size: int,\n/app/solution/train_current_model.py:1882:    for start in range(0, len(eligibility.uids), ranking_batch_size):\n/app/solution/train_current_model.py:1883:        end = min(start + ranking_batch_size, len(eligibility.uids))\n/app/solution/train_current_model.py:1896:                (uid, int(prepared.item_ids[column]), rank)\n/app/solution/train_current_model.py:1897:                for rank, column in enumerate(columns, start=1)\n/app/solution/train_current_model.py:1900:            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n/app/solution/train_current_model.py:1909:    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n/app/solution/train_current_model.py:1912:def write_ranking(frame: pd.DataFrame, output: Path) -> None:\n/app/solution/train_current_model.py:1923:    parser = argparse.ArgumentParser(description=__doc__)\n/app/solution/train_current_model.py:1925:        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n/app/solution/train_current_model.py:1939:        \"--loss-microbatch-size\",\n/app/solution/train_current_model.py:1941:        default=Config.loss_microbatch_size,\n/app/solution/train_current_model.py:1944:        \"--negative-filter-scope\",\n/app/solution/train_current_model.py:1946:        default=Config.negative_filter_scope,\n/app/solution/train_current_model.py:2003:    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n/app/solution/train_current_model.py:2012:        or args.loss_microbatch_size < 1\n/app/solution/train_current_model.py:2028:    config = Config(\n/app/solution/train_current_model.py:2033:        loss_microbatch_size=args.loss_microbatch_size,\n/app/solution/train_current_model.py:2034:        negative_filter_scope=args.negative_filter_scope,\n/app/solution/train_current_model.py:2057:        args.stage,\n/app/solution/train_current_model.py:2071:                    \"stage\": args.stage,\n/app/solution/train_current_model.py:2095:        args.stage,\n/app/solution/train_current_model.py:2102:    ranking, embedding_diagnostics = rank_candidates(\n/app/solution/train_current_model.py:2108:        args.ranking_batch_size,\n/app/solution/train_current_model.py:2110:    write_ranking(ranking, args.output.resolve())\n/app/solution/train_current_model.py:2115:                \"stage\": args.stage,\n/app/solution/train_current_model.py:2117:                \"rows\": len(ranking),\n/app/solution/train_current_model.py:2118:                \"users\": int(ranking.uid.nunique()),\n/app/solution/train_current_model.py:2126:                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n/app/solution/train_current_model.py:2129:                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n/app/solution/train_current_model.py:2135:                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n/app/solution/train_current_model.py:2136:                    \"negative_sampling\": (\n/app/solution/train_current_model.py:2139:                    \"false_negative_filter\": config.negative_filter_scope,\n    dislike_count: int,\n) -> np.ndarray:\n    start = int(\n        np.searchsorted(\n            timestamps,\n            history_end - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n            side=\"left\",\n        )\n    )\n    result = np.zeros(6, dtype=np.float32)\n    recent_items = items[start:]\n    if len(recent_items):\n        result[0] = np.log1p(len(recent_items)) / 8.0\n        result[1] = np.log1p(len(np.unique(recent_items))) / 6.0\n        result[2] = float(np.mean(event_features[start:, 0]))\n        result[3] = float(np.mean(event_features[start:, 1]))\n    result[4] = np.log1p(like_count) / 6.0\n    result[5] = np.log1p(dislike_count) / 4.0\n    return result\n\n\ndef prepare_data(\n    public: Path, stage: str, config: Config\n) -> tuple[SequenceData, CandidateSet]:\n    data = public / \"data\"\n    catalog = pd.read_parquet(data / \"candidate_catalog.parquet\").sort_values(\n        \"popularity_rank\"\n    )\n    item_ids = catalog.item_id.to_numpy(dtype=np.int64, copy=True)\n    item_index = pd.Index(item_ids)\n    n_items = len(item_ids)\n    if n_items >= np.iinfo(np.uint16).max:\n        raise RuntimeError(\"uint16 item storage is too small for this catalog\")\n\n    if stage == \"validation\":\n        prefixes = (\"train\",)\n        history_end = base.TRAIN_END\n        candidate_name = \"validation_eligible_candidates.npz\"\n        state_name = \"validation_preference_state.parquet\"\n    else:\n        prefixes = (\"train\", \"val\")\n        history_end = base.VALIDATION_END\n        candidate_name = \"test_eligible_candidates.npz\"\n        state_name = \"test_preference_state.parquet\"\n    eligibility = CandidateSet.read(data / candidate_name)\n    if not np.array_equal(eligibility.item_ids, item_ids):\n        raise RuntimeError(\"catalog and candidate artifact item order differ\")\n\n    explicit_by_user = base.load_explicit_events(data, prefixes, item_index)\n    inference_likes, inference_dislikes, like_counts, dislike_counts = (\n        base.load_inference_state(\n            data / state_name,\n            item_index,\n            eligibility.uids,\n            n_items,\n        )\n    )\n    inference_rows = {int(uid): row for row, uid in enumerate(eligibility.uids)}\n    inference_user_features = np.zeros((len(eligibility.uids), 6), dtype=np.float32)\n    inference_sequence_rows = np.full(len(eligibility.uids), -1, dtype=np.int32)\n\n    # Snapshot zero is the shared empty explicit state.\n    liked_states = [np.full(base.LIKE_ITEMS, n_items, dtype=np.uint16)]\n    disliked_states = [\n        np.full(base.DISLIKE_ITEMS, n_items, dtype=np.uint16)\n    ]\n    state_counts: list[tuple[int, int]] = [(0, 0)]\n    user_ids: list[int] = []\n    offsets = [0]\n    timestamp_parts: list[np.ndarray] = []\n    item_parts: list[np.ndarray] = []\n    event_parts: list[np.ndarray] = []\n    activity_parts: list[np.ndarray] = []\n    state_parts: list[np.ndarray] = []\n\n    listen_paths = [data / f\"{prefix}_listens.parquet\" for prefix in prefixes]\n    started = time.monotonic()\n    for seen_users, (uid, listens) in enumerate(\n        base.merge_listen_streams(listen_paths, item_index), start=1\n    ):\n        parts = build_sequence_parts(\n            listens,\n            explicit_by_user.get(uid, base.empty_explicit_events()),\n            n_items,\n            liked_states,\n            disliked_states,\n            state_counts,\n        )\n        if parts is None:\n            continue\n        sequence_row = len(user_ids)\n        user_ids.append(uid)\n        timestamp_parts.append(parts[0].astype(np.uint32, copy=False))\n        item_parts.append(parts[1])\n        event_parts.append(parts[2])\n        activity_parts.append(parts[3])\n        state_parts.append(parts[4])\n        offsets.append(offsets[-1] + len(parts[1]))\n        inference_row = inference_rows.get(uid)\n        if inference_row is not None:\n            inference_sequence_rows[inference_row] = sequence_row\n            inference_user_features[inference_row] = final_user_features(\n                parts[0],\n                parts[1],\n                parts[2],\n                history_end,\n                int(like_counts[inference_row]),\n                int(dislike_counts[inference_row]),\n            )\n        if seen_users % 1_000 == 0:\n            log(\n                f\"prepared users={seen_users:,} tokens={offsets[-1]:,} \"\n                f\"states={len(liked_states):,} \"\n                f\"elapsed={time.monotonic() - started:.1f}s\"\n            )\n\n    missing = np.flatnonzero(inference_sequence_rows < 0)\n    if len(missing):\n        inference_user_features[missing, 4] = np.log1p(like_counts[missing]) / 6.0\n        inference_user_features[missing, 5] = (\n            np.log1p(dislike_counts[missing]) / 4.0\n        )\n        log(f\"target users without qualifying catalog sequence={len(missing):,}\")\n\n    prepared = SequenceData(\n        item_ids=item_ids,\n        item_features=base.build_item_features(catalog),\n        user_ids=np.asarray(user_ids, dtype=np.int64),\n        offsets=np.asarray(offsets, dtype=np.int64),\n        sequence_timestamps=np.concatenate(timestamp_parts),\n        sequence_items=np.concatenate(item_parts),\n        event_features=np.concatenate(event_parts),\n        activity_features=np.concatenate(activity_parts),\n        state_ids=np.concatenate(state_parts),\n        liked_states=np.stack(liked_states),\n        disliked_states=np.stack(disliked_states),\n        state_counts=np.asarray(state_counts, dtype=np.int32),\n        inference_user_rows=inference_sequence_rows,\n        inference_liked_items=inference_likes,\n        inference_disliked_items=inference_dislikes,\n        inference_user_features=inference_user_features,\n    )\n    log(\n        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n        f\"tokens={len(prepared.sequence_items):,} \"\n        f\"next_item_targets={prepared.target_count:,} \"\n        f\"states={len(prepared.liked_states):,}\"\n    )\n    return prepared, eligibility\n\n\ndef cache_metadata(stage: str, config: Config) -> dict[str, object]:\n    return {\n        \"cache_version\": CACHE_VERSION,\n        \"stage\": stage,\n        \"positive_listen_threshold\": base.LISTEN_POSITIVE_THRESHOLD,\n        \"profile_lookback_days\": base.PROFILE_LOOKBACK_DAYS,\n        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n    }\n\n\ndef save_cache(\n    path: Path, prepared: SequenceData, stage: str, config: Config\n) -> None:\n    path.parent.mkdir(parents=True, exist_ok=True)\n    np.savez(\n        path,\n        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n        **prepared.__dict__,\n    )\n    log(f\"saved public-derived full-sequence cache: {path}\")\n\n\ndef load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n    with np.load(path, allow_pickle=False) as artifact:\n        actual = json.loads(str(artifact[\"metadata\"].item()))\n        expected = cache_metadata(stage, config)\n        if actual != expected:\n            raise RuntimeError(f\"sequence cache differs: {actual} != {expected}\")\n        values = {\n            field: artifact[field].copy()\n            for field in SequenceData.__dataclass_fields__\n        }\n    prepared = SequenceData(**values)\n    log(\n        f\"loaded full-sequence cache: tokens={len(prepared.sequence_items):,} \"\n        f\"targets={prepared.target_count:,}\"\n    )\n    return prepared\n\n\ndef load_or_prepare(\n    public: Path,\n    stage: str,\n    config: Config,\n    cache: Path | None,\n) -> tuple[SequenceData, CandidateSet]:\n    candidate_name = (\n        \"validation_eligible_candidates.npz\"\n        if stage == \"validation\"\n        else \"test_eligible_candidates.npz\"\n    )\n    eligibility = CandidateSet.read(public / \"data\" / candidate_name)\n    if cache is not None and cache.is_file():\n        prepared = load_cache(cache, stage, config)\n        if not np.array_equal(prepared.item_ids, eligibility.item_ids):\n            raise RuntimeError(\"cached catalog differs from candidate artifact\")\n        return prepared, eligibility\n    prepared, built_eligibility = prepare_data(public, stage, config)\n    if cache is not None:\n        save_cache(cache, prepared, stage, config)\n    return prepared, built_eligibility\n\n\ndef build_item_correction(\n    prepared: SequenceData,\n    config: Config,\n    target_starts: np.ndarray,\n    target_counts: np.ndarray,\n) -> torch.Tensor:\n    \"\"\"Estimate in-batch propensities from the selected training targets.\"\"\"\n    counts = np.zeros(len(prepared.item_ids), dtype=np.float64)\n    for user_row, count in enumerate(target_counts):\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        target_start = int(target_starts[user_row])\n        counts += np.bincount(\n            prepared.sequence_items[\n                offset\n                + target_start\n                + 1 : offset\n                + target_start\n                + int(count)\n                + 1\n            ].astype(np.int64),\n            minlength=len(prepared.item_ids),\n        )\n    total = float(counts.sum())\n    probabilities = (counts + 1.0) / (total + len(counts))\n    raw = np.power(\n        (1.0 / len(counts)) / probabilities,\n        config.inbatch_correction_power,\n    )\n    normalization = float(np.sum(counts * raw) / max(total, 1.0))\n    correction = np.clip(\n        raw / max(normalization, 1.0e-12),\n        config.inbatch_correction_min,\n        config.inbatch_correction_max,\n    ).astype(np.float32)\n    mean_on_targets = float(np.sum(counts * correction) / max(total, 1.0))\n    log(\n        f\"inbatch correction: min={correction.min():.3f} \"\n        f\"mean_on_targets={mean_on_targets:.3f} max={correction.max():.3f}\"\n    )\n    return torch.from_numpy(correction)\n\n\ndef build_known_positive_filter(\n    prepared: SequenceData, training_counts: np.ndarray\n) -> np.ndarray:\n    \"\"\"Pack each user's complete public-training positive-item set.\"\"\"\n    width = (len(prepared.item_ids) + 7) // 8\n    packed = np.zeros((len(prepared.user_ids), width), dtype=np.uint8)\n    retained = 0\n    for user_row, target_count in enumerate(training_counts):\n        if not target_count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        # T adjacent targets consume sequence positions 0 through T.  The\n        # chronological BCE suffix starts at T + 1 and is intentionally absent.\n        items = np.unique(\n            prepared.sequence_items[\n                offset : offset + int(target_count) + 1\n            ].astype(np.int64)\n        )\n        byte_columns = items >> 3\n        bit_values = np.left_shift(\n            np.uint8(1), (items & 7).astype(np.uint8)\n        )\n        np.bitwise_or.at(packed[user_row], byte_columns, bit_values)\n        retained += len(items)\n    log(\n        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n        f\"unique_user_items={retained:,} bytes={packed.nbytes:,}\"\n    )\n    return packed\n\n\ndef invalid_full_history_negatives(\n    negatives: np.ndarray,\n    targets: np.ndarray,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray,\n    liked_items: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n    byte_columns = negatives >> 3\n    bit_columns = negatives & 7\n    known = known_positive_packed[user_rows[:, None], byte_columns]\n    invalid = ((known >> bit_columns) & 1).astype(bool)\n    invalid |= negatives == targets[:, None]\n    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= (\n            negatives[:, column, None] == negatives[:, :column]\n        ).any(axis=1)\n    return invalid\n\n\ndef draw_full_history_filtered_negatives(\n    targets: torch.Tensor,\n    user_rows: np.ndarray,\n    liked_items: torch.Tensor,\n    known_positive_packed: np.ndarray,\n    n_items: int,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n    targets_cpu = targets.detach().cpu().numpy().astype(np.int64, copy=False)\n    liked_cpu = liked_items.detach().cpu().numpy().astype(np.int64, copy=False)\n    batch_size = len(targets_cpu)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, config.uniform_negatives),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n    corrected_count = 0\n    if config.inbatch_negatives:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(\n            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n        )\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(\n                    torch.from_numpy(targets_cpu)[:, None]\n                ),\n                -1.0,\n            )\n            columns = torch.topk(\n                priorities, k=corrected_count, dim=1\n            ).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < config.inbatch_negatives:\n            filler = torch.randint(\n                n_items,\n                (batch_size, config.inbatch_negatives - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n    correction = np.ones_like(negatives, dtype=np.float32)\n    if corrected_count:\n        correction[\n            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]].numpy()\n    for _ in range(32):\n        invalid = invalid_full_history_negatives(\n            negatives,\n            targets_cpu,\n            user_rows,\n            known_positive_packed,\n            liked_cpu,\n        )\n        if not np.any(invalid):\n            return (\n                torch.from_numpy(negatives).to(device),\n                torch.from_numpy(correction).to(device),\n            )\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum()),),\n            generator=generator,\n            device=\"cpu\",\n        ).numpy()\n        negatives[invalid] = replacements\n        # Rejected in-batch items become ordinary uniform draws.\n        correction[invalid] = 1.0\n    invalid = invalid_full_history_negatives(\n        negatives,\n        targets_cpu,\n        user_rows,\n        known_positive_packed,\n        liked_cpu,\n    )\n    if np.any(invalid):\n        raise RuntimeError(\"full-history negative resampling failed\")\n    return (\n        torch.from_numpy(negatives).to(device),\n        torch.from_numpy(correction).to(device),\n    )\n\n\ndef draw_training_negatives(\n    positive_items: torch.Tensor,\n    known_history: torch.Tensor,\n    liked_items: torch.Tensor,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray | None,\n    prepared: SequenceData,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    if config.negative_filter_scope == \"full-training-history\":\n        if known_positive_packed is None:\n            raise RuntimeError(\"full-history negative filter was not built\")\n        return draw_full_history_filtered_negatives(\n            positive_items,\n            user_rows,\n            liked_items,\n            known_positive_packed,\n            len(prepared.item_ids),\n            config,\n            item_correction,\n            generator,\n            device,\n        )\n    return base.draw_filtered_mixed_negatives(\n        positive_items,\n        known_history,\n        liked_items,\n        len(prepared.item_ids),\n        config.uniform_negatives,\n        config.inbatch_negatives,\n        item_correction,\n        generator,\n        device,\n    )\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_1, config.item_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_2, dim),\n        )\n        nn.init.normal_(self.context_embedding.weight, std=0.02)\n        nn.init.normal_(self.candidate_embedding.weight, std=0.02)\n        with torch.no_grad():\n            self.context_embedding.weight[n_items].zero_()\n\n    def _mean_context_channel(self, items: torch.Tensor) -> torch.Tensor:\n        mask = items.ne(self.n_items)\n        vectors = self.context_embedding(items)\n        return (vectors * mask.unsqueeze(-1)).sum(dim=1) / mask.sum(\n            dim=1, keepdim=True\n        ).clamp_min(1)\n\n    def encode_items(self, items: torch.Tensor) -> torch.Tensor:\n        inputs = torch.cat(\n            [self.candidate_embedding(items), self.item_features[items]], dim=1\n        )\n        return self.item_tower(inputs)\n\n\ndef invalid_negative_mask(\n    negatives: torch.Tensor,\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n) -> torch.Tensor:\n    \"\"\"Identify targets, known positives, active likes, and row duplicates.\"\"\"\n    invalid = negatives.eq(targets[:, None])\n    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= negatives[:, column, None].eq(\n            negatives[:, :column]\n        ).any(dim=1)\n    return invalid\n\n\ndef draw_filtered_mixed_negatives(\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n    n_items: int,\n    uniform_count: int,\n    inbatch_count: int,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n    batch_size = len(targets)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, uniform_count),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long, device=\"cpu\")\n    corrected_count = 0\n    if inbatch_count:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(inbatch_count, max(len(unique_targets) - 1, 0))\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(targets.detach().cpu()[:, None]),\n                -1.0,\n            )\n            columns = torch.topk(priorities, k=corrected_count, dim=1).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < inbatch_count:\n            filler = torch.randint(\n                n_items,\n                (batch_size, inbatch_count - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n    if corrected_count:\n        correction_cpu[\n            :, uniform_count : uniform_count + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]]\n    negatives = negatives_cpu.to(device)\n    correction = correction_cpu.to(device)\n    for _ in range(32):\n        invalid = invalid_negative_mask(\n            negatives, targets, context_items, liked_items\n        )\n        if not bool(invalid.any()):\n            return negatives, correction\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum().detach().cpu()),),\n            generator=generator,\n            device=\"cpu\",\n        ).to(device)\n        negatives[invalid] = replacements\n        correction[invalid] = 1.0\n    invalid = invalid_negative_mask(\n        negatives, targets, context_items, liked_items\n    )\n    if bool(invalid.any()):\n        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n    return negatives, correction\n",
              "stderr": "",
              "aggregated_output": "/app/solution/two_tower_model.py:40:    uniform_negatives: int = 24\n/app/solution/two_tower_model.py:41:    inbatch_negatives: int = 8\n/app/solution/two_tower_model.py:73:    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n/app/solution/two_tower_model.py:79:            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n/app/solution/two_tower_model.py:346:def invalid_negative_mask(\n/app/solution/two_tower_model.py:347:    negatives: torch.Tensor,\n/app/solution/two_tower_model.py:353:    invalid = negatives.eq(targets[:, None])\n/app/solution/two_tower_model.py:354:    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:355:    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:356:    for column in range(1, negatives.shape[1]):\n/app/solution/two_tower_model.py:357:        invalid[:, column] |= negatives[:, column, None].eq(\n/app/solution/two_tower_model.py:358:            negatives[:, :column]\n/app/solution/two_tower_model.py:363:def draw_filtered_mixed_negatives(\n/app/solution/two_tower_model.py:374:    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n/app/solution/two_tower_model.py:406:    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n/app/solution/two_tower_model.py:407:    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n/app/solution/two_tower_model.py:412:    negatives = negatives_cpu.to(device)\n/app/solution/two_tower_model.py:415:        invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:416:            negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:419:            return negatives, correction\n/app/solution/two_tower_model.py:426:        negatives[invalid] = replacements\n/app/solution/two_tower_model.py:428:    invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:429:        negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:432:        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n/app/solution/two_tower_model.py:433:    return negatives, correction\n/app/solution/train_current_model.py:6:loss.  The fast default retains each user's most recent 128 training targets and\n/app/solution/train_current_model.py:9:computes all of its timestep losses and carries the detached GRU hidden state\n/app/solution/train_current_model.py:13:normalization, raw dot-product retrieval, sample-weighted binary cross entropy,\n/app/solution/train_current_model.py:14:and 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\n/app/solution/train_current_model.py:20:import argparse\n/app/solution/train_current_model.py:55:    loss_microbatch_size: int = 65_536\n/app/solution/train_current_model.py:56:    uniform_negatives: int = 24\n/app/solution/train_current_model.py:57:    inbatch_negatives: int = 8\n/app/solution/train_current_model.py:61:    negative_filter_scope: str = \"full-training-history\"\n/app/solution/train_current_model.py:152:    return base.TowerConfig(\n/app/solution/train_current_model.py:165:        uniform_negatives=config.uniform_negatives,\n/app/solution/train_current_model.py:166:        inbatch_negatives=config.inbatch_negatives,\n/app/solution/train_current_model.py:342:    public: Path, stage: str, config: Config\n/app/solution/train_current_model.py:346:        \"popularity_rank\"\n/app/solution/train_current_model.py:354:    if stage == \"validation\":\n/app/solution/train_current_model.py:463:        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:471:def cache_metadata(stage: str, config: Config) -> dict[str, object]:\n/app/solution/train_current_model.py:474:        \"stage\": stage,\n/app/solution/train_current_model.py:477:        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n/app/solution/train_current_model.py:482:    path: Path, prepared: SequenceData, stage: str, config: Config\n/app/solution/train_current_model.py:487:        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n/app/solution/train_current_model.py:493:def load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n/app/solution/train_current_model.py:496:        expected = cache_metadata(stage, config)\n/app/solution/train_current_model.py:513:    stage: str,\n/app/solution/train_current_model.py:519:        if stage == \"validation\"\n/app/solution/train_current_model.py:524:        prepared = load_cache(cache, stage, config)\n/app/solution/train_current_model.py:528:    prepared, built_eligibility = prepare_data(public, stage, config)\n/app/solution/train_current_model.py:530:        save_cache(cache, prepared, stage, config)\n/app/solution/train_current_model.py:603:        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:609:def invalid_full_history_negatives(\n/app/solution/train_current_model.py:610:    negatives: np.ndarray,\n/app/solution/train_current_model.py:616:    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n/app/solution/train_current_model.py:617:    byte_columns = negatives >> 3\n/app/solution/train_current_model.py:618:    bit_columns = negatives & 7\n/app/solution/train_current_model.py:621:    invalid |= negatives == targets[:, None]\n/app/solution/train_current_model.py:622:    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n/app/solution/train_current_model.py:623:    for column in range(1, negatives.shape[1]):\n/app/solution/train_current_model.py:625:            negatives[:, column, None] == negatives[:, :column]\n/app/solution/train_current_model.py:630:def draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:641:    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n/app/solution/train_current_model.py:647:        (batch_size, config.uniform_negatives),\n/app/solution/train_current_model.py:653:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:656:            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n/app/solution/train_current_model.py:672:        if corrected_count < config.inbatch_negatives:\n/app/solution/train_current_model.py:675:                (batch_size, config.inbatch_negatives - corrected_count),\n/app/solution/train_current_model.py:681:    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n/app/solution/train_current_model.py:682:    correction = np.ones_like(negatives, dtype=np.float32)\n/app/solution/train_current_model.py:685:            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n/app/solution/train_current_model.py:688:        invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:689:            negatives,\n/app/solution/train_current_model.py:697:                torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:706:        negatives[invalid] = replacements\n/app/solution/train_current_model.py:709:    invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:710:        negatives,\n/app/solution/train_current_model.py:717:        raise RuntimeError(\"full-history negative resampling failed\")\n/app/solution/train_current_model.py:719:        torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:724:def draw_training_negatives(\n/app/solution/train_current_model.py:736:    if config.negative_filter_scope == \"full-training-history\":\n/app/solution/train_current_model.py:738:            raise RuntimeError(\"full-history negative filter was not built\")\n/app/solution/train_current_model.py:739:        return draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:750:    return base.draw_filtered_mixed_negatives(\n/app/solution/train_current_model.py:755:        config.uniform_negatives,\n/app/solution/train_current_model.py:756:        config.inbatch_negatives,\n/app/solution/train_current_model.py:816:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:818:    all_items = torch.cat([positives, negatives.reshape(-1)])\n/app/solution/train_current_model.py:822:    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n/app/solution/train_current_model.py:823:        len(positives), negatives.shape[1], -1\n/app/solution/train_current_model.py:825:    return positive_vectors, negative_vectors\n/app/solution/train_current_model.py:845:def corrected_negative_loss(\n/app/solution/train_current_model.py:851:    total = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:853:    if config.uniform_negatives:\n/app/solution/train_current_model.py:854:        result += config.uniform_negatives * raw[\n/app/solution/train_current_model.py:855:            :, : config.uniform_negatives\n/app/solution/train_current_model.py:857:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:858:        selected = slice(config.uniform_negatives, total)\n/app/solution/train_current_model.py:860:        result += config.inbatch_negatives * (\n/app/solution/train_current_model.py:880:        raise RuntimeError(\"chronological target partition produced negative counts\")\n/app/solution/train_current_model.py:915:    public: Path, stage: str, item_ids: np.ndarray\n/app/solution/train_current_model.py:918:    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n/app/solution/train_current_model.py:957:    stage: str,\n/app/solution/train_current_model.py:978:                public, stage, prepared.item_ids\n/app/solution/train_current_model.py:981:                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n/app/solution/train_current_model.py:1119:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:1120:    negative_weights: torch.Tensor,\n/app/solution/train_current_model.py:1121:    sample_weights: np.ndarray,\n/app/solution/train_current_model.py:1127:    total_weight = float(sample_weights.sum())\n/app/solution/train_current_model.py:1129:        raise RuntimeError(\"target block has no positive sample weight\")\n/app/solution/train_current_model.py:1132:        \"loss_sum\": 0.0,\n/app/solution/train_current_model.py:1134:        \"negative_sum\": 0.0,\n/app/solution/train_current_model.py:1138:    for begin in range(0, target_count, config.loss_microbatch_size):\n/app/solution/train_current_model.py:1139:        end = min(begin + config.loss_microbatch_size, target_count)\n/app/solution/train_current_model.py:1162:        positive_vectors, negative_vectors = candidate_vectors(\n/app/solution/train_current_model.py:1165:            negatives[begin:end],\n/app/solution/train_current_model.py:1168:        negative_logits = torch.einsum(\n/app/solution/train_current_model.py:1169:            \"bd,bkd->bk\", query_vectors, negative_vectors\n/app/solution/train_current_model.py:1171:        positive_loss = F.softplus(-positive_logits)\n/app/solution/train_current_model.py:1172:        negative_loss = corrected_negative_loss(\n/app/solution/train_current_model.py:1173:            negative_logits, negative_weights[begin:end], config\n/app/solution/train_current_model.py:1176:            sample_weights[begin:end].astype(np.float32, copy=False)\n/app/solution/train_current_model.py:1178:        loss_sum = (\n/app/solution/train_current_model.py:1179:            selected_weights * (positive_loss + negative_loss) / 2.0\n/app/solution/train_current_model.py:1181:        if not bool(torch.isfinite(loss_sum)):\n/app/solution/train_current_model.py:1182:            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n/app/solution/train_current_model.py:1184:            (loss_sum / total_weight).backward()\n/app/solution/train_current_model.py:1188:        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n/app/solution/train_current_model.py:1190:        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n/app/solution/train_current_model.py:1192:            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n/app/solution/train_current_model.py:1227:    negative_count = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:1228:    total_loss = 0.0\n/app/solution/train_current_model.py:1232:    total_negative = 0.0\n/app/solution/train_current_model.py:1293:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1314:                negatives,\n/app/solution/train_current_model.py:1315:                negative_weights,\n/app/solution/train_current_model.py:1327:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1331:            total_negative += statistics[\"negative_sum\"]\n/app/solution/train_current_model.py:1337:                batch_bce = statistics[\"loss_sum\"] / max(\n/app/solution/train_current_model.py:1340:                running_bce = total_loss / max(total_weight, 1.0e-12)\n/app/solution/train_current_model.py:1351:        \"loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1353:        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1355:        / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1388:    total_loss = 0.0\n/app/solution/train_current_model.py:1449:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1469:                negatives,\n/app/solution/train_current_model.py:1470:                negative_weights,\n/app/solution/train_current_model.py:1475:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1481:        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1523:    stage: str,\n/app/solution/train_current_model.py:1560:        stage,\n/app/solution/train_current_model.py:1567:        if config.negative_filter_scope == \"full-training-history\"\n/app/solution/train_current_model.py:1571:    best_loss = float(\"inf\")\n/app/solution/train_current_model.py:1601:            \"negative_filter_scope\", \"last-100\"\n/app/solution/train_current_model.py:1629:            stored_filter_scope != config.negative_filter_scope\n/app/solution/train_current_model.py:1657:            prior.pop(\"validation_loss\", None)\n/app/solution/train_current_model.py:1660:                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n/app/solution/train_current_model.py:1666:        if \"validation_loss\" not in prior:\n/app/solution/train_current_model.py:1682:        best_loss = float(prior[\"validation_loss\"])\n/app/solution/train_current_model.py:1687:            f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1731:            diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1732:            < best_loss - config.early_stopping_min_delta\n/app/solution/train_current_model.py:1735:            best_loss = diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1754:            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n/app/solution/train_current_model.py:1755:            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n/app/solution/train_current_model.py:1766:                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1776:        f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1861:def rank_candidates(\n/app/solution/train_current_model.py:1867:    ranking_batch_size: int,\n/app/solution/train_current_model.py:1882:    for start in range(0, len(eligibility.uids), ranking_batch_size):\n/app/solution/train_current_model.py:1883:        end = min(start + ranking_batch_size, len(eligibility.uids))\n/app/solution/train_current_model.py:1896:                (uid, int(prepared.item_ids[column]), rank)\n/app/solution/train_current_model.py:1897:                for rank, column in enumerate(columns, start=1)\n/app/solution/train_current_model.py:1900:            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n/app/solution/train_current_model.py:1909:    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n/app/solution/train_current_model.py:1912:def write_ranking(frame: pd.DataFrame, output: Path) -> None:\n/app/solution/train_current_model.py:1923:    parser = argparse.ArgumentParser(description=__doc__)\n/app/solution/train_current_model.py:1925:        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n/app/solution/train_current_model.py:1939:        \"--loss-microbatch-size\",\n/app/solution/train_current_model.py:1941:        default=Config.loss_microbatch_size,\n/app/solution/train_current_model.py:1944:        \"--negative-filter-scope\",\n/app/solution/train_current_model.py:1946:        default=Config.negative_filter_scope,\n/app/solution/train_current_model.py:2003:    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n/app/solution/train_current_model.py:2012:        or args.loss_microbatch_size < 1\n/app/solution/train_current_model.py:2028:    config = Config(\n/app/solution/train_current_model.py:2033:        loss_microbatch_size=args.loss_microbatch_size,\n/app/solution/train_current_model.py:2034:        negative_filter_scope=args.negative_filter_scope,\n/app/solution/train_current_model.py:2057:        args.stage,\n/app/solution/train_current_model.py:2071:                    \"stage\": args.stage,\n/app/solution/train_current_model.py:2095:        args.stage,\n/app/solution/train_current_model.py:2102:    ranking, embedding_diagnostics = rank_candidates(\n/app/solution/train_current_model.py:2108:        args.ranking_batch_size,\n/app/solution/train_current_model.py:2110:    write_ranking(ranking, args.output.resolve())\n/app/solution/train_current_model.py:2115:                \"stage\": args.stage,\n/app/solution/train_current_model.py:2117:                \"rows\": len(ranking),\n/app/solution/train_current_model.py:2118:                \"users\": int(ranking.uid.nunique()),\n/app/solution/train_current_model.py:2126:                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n/app/solution/train_current_model.py:2129:                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n/app/solution/train_current_model.py:2135:                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n/app/solution/train_current_model.py:2136:                    \"negative_sampling\": (\n/app/solution/train_current_model.py:2139:                    \"false_negative_filter\": config.negative_filter_scope,\n    dislike_count: int,\n) -> np.ndarray:\n    start = int(\n        np.searchsorted(\n            timestamps,\n            history_end - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n            side=\"left\",\n        )\n    )\n    result = np.zeros(6, dtype=np.float32)\n    recent_items = items[start:]\n    if len(recent_items):\n        result[0] = np.log1p(len(recent_items)) / 8.0\n        result[1] = np.log1p(len(np.unique(recent_items))) / 6.0\n        result[2] = float(np.mean(event_features[start:, 0]))\n        result[3] = float(np.mean(event_features[start:, 1]))\n    result[4] = np.log1p(like_count) / 6.0\n    result[5] = np.log1p(dislike_count) / 4.0\n    return result\n\n\ndef prepare_data(\n    public: Path, stage: str, config: Config\n) -> tuple[SequenceData, CandidateSet]:\n    data = public / \"data\"\n    catalog = pd.read_parquet(data / \"candidate_catalog.parquet\").sort_values(\n        \"popularity_rank\"\n    )\n    item_ids = catalog.item_id.to_numpy(dtype=np.int64, copy=True)\n    item_index = pd.Index(item_ids)\n    n_items = len(item_ids)\n    if n_items >= np.iinfo(np.uint16).max:\n        raise RuntimeError(\"uint16 item storage is too small for this catalog\")\n\n    if stage == \"validation\":\n        prefixes = (\"train\",)\n        history_end = base.TRAIN_END\n        candidate_name = \"validation_eligible_candidates.npz\"\n        state_name = \"validation_preference_state.parquet\"\n    else:\n        prefixes = (\"train\", \"val\")\n        history_end = base.VALIDATION_END\n        candidate_name = \"test_eligible_candidates.npz\"\n        state_name = \"test_preference_state.parquet\"\n    eligibility = CandidateSet.read(data / candidate_name)\n    if not np.array_equal(eligibility.item_ids, item_ids):\n        raise RuntimeError(\"catalog and candidate artifact item order differ\")\n\n    explicit_by_user = base.load_explicit_events(data, prefixes, item_index)\n    inference_likes, inference_dislikes, like_counts, dislike_counts = (\n        base.load_inference_state(\n            data / state_name,\n            item_index,\n            eligibility.uids,\n            n_items,\n        )\n    )\n    inference_rows = {int(uid): row for row, uid in enumerate(eligibility.uids)}\n    inference_user_features = np.zeros((len(eligibility.uids), 6), dtype=np.float32)\n    inference_sequence_rows = np.full(len(eligibility.uids), -1, dtype=np.int32)\n\n    # Snapshot zero is the shared empty explicit state.\n    liked_states = [np.full(base.LIKE_ITEMS, n_items, dtype=np.uint16)]\n    disliked_states = [\n        np.full(base.DISLIKE_ITEMS, n_items, dtype=np.uint16)\n    ]\n    state_counts: list[tuple[int, int]] = [(0, 0)]\n    user_ids: list[int] = []\n    offsets = [0]\n    timestamp_parts: list[np.ndarray] = []\n    item_parts: list[np.ndarray] = []\n    event_parts: list[np.ndarray] = []\n    activity_parts: list[np.ndarray] = []\n    state_parts: list[np.ndarray] = []\n\n    listen_paths = [data / f\"{prefix}_listens.parquet\" for prefix in prefixes]\n    started = time.monotonic()\n    for seen_users, (uid, listens) in enumerate(\n        base.merge_listen_streams(listen_paths, item_index), start=1\n    ):\n        parts = build_sequence_parts(\n            listens,\n            explicit_by_user.get(uid, base.empty_explicit_events()),\n            n_items,\n            liked_states,\n            disliked_states,\n            state_counts,\n        )\n        if parts is None:\n            continue\n        sequence_row = len(user_ids)\n        user_ids.append(uid)\n        timestamp_parts.append(parts[0].astype(np.uint32, copy=False))\n        item_parts.append(parts[1])\n        event_parts.append(parts[2])\n        activity_parts.append(parts[3])\n        state_parts.append(parts[4])\n        offsets.append(offsets[-1] + len(parts[1]))\n        inference_row = inference_rows.get(uid)\n        if inference_row is not None:\n            inference_sequence_rows[inference_row] = sequence_row\n            inference_user_features[inference_row] = final_user_features(\n                parts[0],\n                parts[1],\n                parts[2],\n                history_end,\n                int(like_counts[inference_row]),\n                int(dislike_counts[inference_row]),\n            )\n        if seen_users % 1_000 == 0:\n            log(\n                f\"prepared users={seen_users:,} tokens={offsets[-1]:,} \"\n                f\"states={len(liked_states):,} \"\n                f\"elapsed={time.monotonic() - started:.1f}s\"\n            )\n\n    missing = np.flatnonzero(inference_sequence_rows < 0)\n    if len(missing):\n        inference_user_features[missing, 4] = np.log1p(like_counts[missing]) / 6.0\n        inference_user_features[missing, 5] = (\n            np.log1p(dislike_counts[missing]) / 4.0\n        )\n        log(f\"target users without qualifying catalog sequence={len(missing):,}\")\n\n    prepared = SequenceData(\n        item_ids=item_ids,\n        item_features=base.build_item_features(catalog),\n        user_ids=np.asarray(user_ids, dtype=np.int64),\n        offsets=np.asarray(offsets, dtype=np.int64),\n        sequence_timestamps=np.concatenate(timestamp_parts),\n        sequence_items=np.concatenate(item_parts),\n        event_features=np.concatenate(event_parts),\n        activity_features=np.concatenate(activity_parts),\n        state_ids=np.concatenate(state_parts),\n        liked_states=np.stack(liked_states),\n        disliked_states=np.stack(disliked_states),\n        state_counts=np.asarray(state_counts, dtype=np.int32),\n        inference_user_rows=inference_sequence_rows,\n        inference_liked_items=inference_likes,\n        inference_disliked_items=inference_dislikes,\n        inference_user_features=inference_user_features,\n    )\n    log(\n        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n        f\"tokens={len(prepared.sequence_items):,} \"\n        f\"next_item_targets={prepared.target_count:,} \"\n        f\"states={len(prepared.liked_states):,}\"\n    )\n    return prepared, eligibility\n\n\ndef cache_metadata(stage: str, config: Config) -> dict[str, object]:\n    return {\n        \"cache_version\": CACHE_VERSION,\n        \"stage\": stage,\n        \"positive_listen_threshold\": base.LISTEN_POSITIVE_THRESHOLD,\n        \"profile_lookback_days\": base.PROFILE_LOOKBACK_DAYS,\n        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n    }\n\n\ndef save_cache(\n    path: Path, prepared: SequenceData, stage: str, config: Config\n) -> None:\n    path.parent.mkdir(parents=True, exist_ok=True)\n    np.savez(\n        path,\n        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n        **prepared.__dict__,\n    )\n    log(f\"saved public-derived full-sequence cache: {path}\")\n\n\ndef load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n    with np.load(path, allow_pickle=False) as artifact:\n        actual = json.loads(str(artifact[\"metadata\"].item()))\n        expected = cache_metadata(stage, config)\n        if actual != expected:\n            raise RuntimeError(f\"sequence cache differs: {actual} != {expected}\")\n        values = {\n            field: artifact[field].copy()\n            for field in SequenceData.__dataclass_fields__\n        }\n    prepared = SequenceData(**values)\n    log(\n        f\"loaded full-sequence cache: tokens={len(prepared.sequence_items):,} \"\n        f\"targets={prepared.target_count:,}\"\n    )\n    return prepared\n\n\ndef load_or_prepare(\n    public: Path,\n    stage: str,\n    config: Config,\n    cache: Path | None,\n) -> tuple[SequenceData, CandidateSet]:\n    candidate_name = (\n        \"validation_eligible_candidates.npz\"\n        if stage == \"validation\"\n        else \"test_eligible_candidates.npz\"\n    )\n    eligibility = CandidateSet.read(public / \"data\" / candidate_name)\n    if cache is not None and cache.is_file():\n        prepared = load_cache(cache, stage, config)\n        if not np.array_equal(prepared.item_ids, eligibility.item_ids):\n            raise RuntimeError(\"cached catalog differs from candidate artifact\")\n        return prepared, eligibility\n    prepared, built_eligibility = prepare_data(public, stage, config)\n    if cache is not None:\n        save_cache(cache, prepared, stage, config)\n    return prepared, built_eligibility\n\n\ndef build_item_correction(\n    prepared: SequenceData,\n    config: Config,\n    target_starts: np.ndarray,\n    target_counts: np.ndarray,\n) -> torch.Tensor:\n    \"\"\"Estimate in-batch propensities from the selected training targets.\"\"\"\n    counts = np.zeros(len(prepared.item_ids), dtype=np.float64)\n    for user_row, count in enumerate(target_counts):\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        target_start = int(target_starts[user_row])\n        counts += np.bincount(\n            prepared.sequence_items[\n                offset\n                + target_start\n                + 1 : offset\n                + target_start\n                + int(count)\n                + 1\n            ].astype(np.int64),\n            minlength=len(prepared.item_ids),\n        )\n    total = float(counts.sum())\n    probabilities = (counts + 1.0) / (total + len(counts))\n    raw = np.power(\n        (1.0 / len(counts)) / probabilities,\n        config.inbatch_correction_power,\n    )\n    normalization = float(np.sum(counts * raw) / max(total, 1.0))\n    correction = np.clip(\n        raw / max(normalization, 1.0e-12),\n        config.inbatch_correction_min,\n        config.inbatch_correction_max,\n    ).astype(np.float32)\n    mean_on_targets = float(np.sum(counts * correction) / max(total, 1.0))\n    log(\n        f\"inbatch correction: min={correction.min():.3f} \"\n        f\"mean_on_targets={mean_on_targets:.3f} max={correction.max():.3f}\"\n    )\n    return torch.from_numpy(correction)\n\n\ndef build_known_positive_filter(\n    prepared: SequenceData, training_counts: np.ndarray\n) -> np.ndarray:\n    \"\"\"Pack each user's complete public-training positive-item set.\"\"\"\n    width = (len(prepared.item_ids) + 7) // 8\n    packed = np.zeros((len(prepared.user_ids), width), dtype=np.uint8)\n    retained = 0\n    for user_row, target_count in enumerate(training_counts):\n        if not target_count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        # T adjacent targets consume sequence positions 0 through T.  The\n        # chronological BCE suffix starts at T + 1 and is intentionally absent.\n        items = np.unique(\n            prepared.sequence_items[\n                offset : offset + int(target_count) + 1\n            ].astype(np.int64)\n        )\n        byte_columns = items >> 3\n        bit_values = np.left_shift(\n            np.uint8(1), (items & 7).astype(np.uint8)\n        )\n        np.bitwise_or.at(packed[user_row], byte_columns, bit_values)\n        retained += len(items)\n    log(\n        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n        f\"unique_user_items={retained:,} bytes={packed.nbytes:,}\"\n    )\n    return packed\n\n\ndef invalid_full_history_negatives(\n    negatives: np.ndarray,\n    targets: np.ndarray,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray,\n    liked_items: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n    byte_columns = negatives >> 3\n    bit_columns = negatives & 7\n    known = known_positive_packed[user_rows[:, None], byte_columns]\n    invalid = ((known >> bit_columns) & 1).astype(bool)\n    invalid |= negatives == targets[:, None]\n    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= (\n            negatives[:, column, None] == negatives[:, :column]\n        ).any(axis=1)\n    return invalid\n\n\ndef draw_full_history_filtered_negatives(\n    targets: torch.Tensor,\n    user_rows: np.ndarray,\n    liked_items: torch.Tensor,\n    known_positive_packed: np.ndarray,\n    n_items: int,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n    targets_cpu = targets.detach().cpu().numpy().astype(np.int64, copy=False)\n    liked_cpu = liked_items.detach().cpu().numpy().astype(np.int64, copy=False)\n    batch_size = len(targets_cpu)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, config.uniform_negatives),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n    corrected_count = 0\n    if config.inbatch_negatives:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(\n            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n        )\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(\n                    torch.from_numpy(targets_cpu)[:, None]\n                ),\n                -1.0,\n            )\n            columns = torch.topk(\n                priorities, k=corrected_count, dim=1\n            ).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < config.inbatch_negatives:\n            filler = torch.randint(\n                n_items,\n                (batch_size, config.inbatch_negatives - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n    correction = np.ones_like(negatives, dtype=np.float32)\n    if corrected_count:\n        correction[\n            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]].numpy()\n    for _ in range(32):\n        invalid = invalid_full_history_negatives(\n            negatives,\n            targets_cpu,\n            user_rows,\n            known_positive_packed,\n            liked_cpu,\n        )\n        if not np.any(invalid):\n            return (\n                torch.from_numpy(negatives).to(device),\n                torch.from_numpy(correction).to(device),\n            )\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum()),),\n            generator=generator,\n            device=\"cpu\",\n        ).numpy()\n        negatives[invalid] = replacements\n        # Rejected in-batch items become ordinary uniform draws.\n        correction[invalid] = 1.0\n    invalid = invalid_full_history_negatives(\n        negatives,\n        targets_cpu,\n        user_rows,\n        known_positive_packed,\n        liked_cpu,\n    )\n    if np.any(invalid):\n        raise RuntimeError(\"full-history negative resampling failed\")\n    return (\n        torch.from_numpy(negatives).to(device),\n        torch.from_numpy(correction).to(device),\n    )\n\n\ndef draw_training_negatives(\n    positive_items: torch.Tensor,\n    known_history: torch.Tensor,\n    liked_items: torch.Tensor,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray | None,\n    prepared: SequenceData,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    if config.negative_filter_scope == \"full-training-history\":\n        if known_positive_packed is None:\n            raise RuntimeError(\"full-history negative filter was not built\")\n        return draw_full_history_filtered_negatives(\n            positive_items,\n            user_rows,\n            liked_items,\n            known_positive_packed,\n            len(prepared.item_ids),\n            config,\n            item_correction,\n            generator,\n            device,\n        )\n    return base.draw_filtered_mixed_negatives(\n        positive_items,\n        known_history,\n        liked_items,\n        len(prepared.item_ids),\n        config.uniform_negatives,\n        config.inbatch_negatives,\n        item_correction,\n        generator,\n        device,\n    )\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_1, config.item_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_2, dim),\n        )\n        nn.init.normal_(self.context_embedding.weight, std=0.02)\n        nn.init.normal_(self.candidate_embedding.weight, std=0.02)\n        with torch.no_grad():\n            self.context_embedding.weight[n_items].zero_()\n\n    def _mean_context_channel(self, items: torch.Tensor) -> torch.Tensor:\n        mask = items.ne(self.n_items)\n        vectors = self.context_embedding(items)\n        return (vectors * mask.unsqueeze(-1)).sum(dim=1) / mask.sum(\n            dim=1, keepdim=True\n        ).clamp_min(1)\n\n    def encode_items(self, items: torch.Tensor) -> torch.Tensor:\n        inputs = torch.cat(\n            [self.candidate_embedding(items), self.item_features[items]], dim=1\n        )\n        return self.item_tower(inputs)\n\n\ndef invalid_negative_mask(\n    negatives: torch.Tensor,\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n) -> torch.Tensor:\n    \"\"\"Identify targets, known positives, active likes, and row duplicates.\"\"\"\n    invalid = negatives.eq(targets[:, None])\n    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= negatives[:, column, None].eq(\n            negatives[:, :column]\n        ).any(dim=1)\n    return invalid\n\n\ndef draw_filtered_mixed_negatives(\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n    n_items: int,\n    uniform_count: int,\n    inbatch_count: int,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n    batch_size = len(targets)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, uniform_count),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long, device=\"cpu\")\n    corrected_count = 0\n    if inbatch_count:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(inbatch_count, max(len(unique_targets) - 1, 0))\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(targets.detach().cpu()[:, None]),\n                -1.0,\n            )\n            columns = torch.topk(priorities, k=corrected_count, dim=1).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < inbatch_count:\n            filler = torch.randint(\n                n_items,\n                (batch_size, inbatch_count - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n    if corrected_count:\n        correction_cpu[\n            :, uniform_count : uniform_count + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]]\n    negatives = negatives_cpu.to(device)\n    correction = correction_cpu.to(device)\n    for _ in range(32):\n        invalid = invalid_negative_mask(\n            negatives, targets, context_items, liked_items\n        )\n        if not bool(invalid.any()):\n            return negatives, correction\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum().detach().cpu()),),\n            generator=generator,\n            device=\"cpu\",\n        ).to(device)\n        negatives[invalid] = replacements\n        correction[invalid] = 1.0\n    invalid = invalid_negative_mask(\n        negatives, targets, context_items, liked_items\n    )\n    if bool(invalid.any()):\n        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n    return negatives, correction\n",
              "exit_code": 0,
              "duration": {
                "secs": 0,
                "nanos": 4570
              },
              "formatted_output": "/app/solution/two_tower_model.py:40:    uniform_negatives: int = 24\n/app/solution/two_tower_model.py:41:    inbatch_negatives: int = 8\n/app/solution/two_tower_model.py:73:    popularity_rank = catalog.popularity_rank.to_numpy(dtype=np.float64, copy=False)\n/app/solution/two_tower_model.py:79:            1.0 - (popularity_rank - 1.0) / max(len(catalog) - 1, 1),\n/app/solution/two_tower_model.py:346:def invalid_negative_mask(\n/app/solution/two_tower_model.py:347:    negatives: torch.Tensor,\n/app/solution/two_tower_model.py:353:    invalid = negatives.eq(targets[:, None])\n/app/solution/two_tower_model.py:354:    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:355:    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n/app/solution/two_tower_model.py:356:    for column in range(1, negatives.shape[1]):\n/app/solution/two_tower_model.py:357:        invalid[:, column] |= negatives[:, column, None].eq(\n/app/solution/two_tower_model.py:358:            negatives[:, :column]\n/app/solution/two_tower_model.py:363:def draw_filtered_mixed_negatives(\n/app/solution/two_tower_model.py:374:    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n/app/solution/two_tower_model.py:406:    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n/app/solution/two_tower_model.py:407:    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n/app/solution/two_tower_model.py:412:    negatives = negatives_cpu.to(device)\n/app/solution/two_tower_model.py:415:        invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:416:            negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:419:            return negatives, correction\n/app/solution/two_tower_model.py:426:        negatives[invalid] = replacements\n/app/solution/two_tower_model.py:428:    invalid = invalid_negative_mask(\n/app/solution/two_tower_model.py:429:        negatives, targets, context_items, liked_items\n/app/solution/two_tower_model.py:432:        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n/app/solution/two_tower_model.py:433:    return negatives, correction\n/app/solution/train_current_model.py:6:loss.  The fast default retains each user's most recent 128 training targets and\n/app/solution/train_current_model.py:9:computes all of its timestep losses and carries the detached GRU hidden state\n/app/solution/train_current_model.py:13:normalization, raw dot-product retrieval, sample-weighted binary cross entropy,\n/app/solution/train_current_model.py:14:and 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\n/app/solution/train_current_model.py:20:import argparse\n/app/solution/train_current_model.py:55:    loss_microbatch_size: int = 65_536\n/app/solution/train_current_model.py:56:    uniform_negatives: int = 24\n/app/solution/train_current_model.py:57:    inbatch_negatives: int = 8\n/app/solution/train_current_model.py:61:    negative_filter_scope: str = \"full-training-history\"\n/app/solution/train_current_model.py:152:    return base.TowerConfig(\n/app/solution/train_current_model.py:165:        uniform_negatives=config.uniform_negatives,\n/app/solution/train_current_model.py:166:        inbatch_negatives=config.inbatch_negatives,\n/app/solution/train_current_model.py:342:    public: Path, stage: str, config: Config\n/app/solution/train_current_model.py:346:        \"popularity_rank\"\n/app/solution/train_current_model.py:354:    if stage == \"validation\":\n/app/solution/train_current_model.py:463:        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:471:def cache_metadata(stage: str, config: Config) -> dict[str, object]:\n/app/solution/train_current_model.py:474:        \"stage\": stage,\n/app/solution/train_current_model.py:477:        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n/app/solution/train_current_model.py:482:    path: Path, prepared: SequenceData, stage: str, config: Config\n/app/solution/train_current_model.py:487:        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n/app/solution/train_current_model.py:493:def load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n/app/solution/train_current_model.py:496:        expected = cache_metadata(stage, config)\n/app/solution/train_current_model.py:513:    stage: str,\n/app/solution/train_current_model.py:519:        if stage == \"validation\"\n/app/solution/train_current_model.py:524:        prepared = load_cache(cache, stage, config)\n/app/solution/train_current_model.py:528:    prepared, built_eligibility = prepare_data(public, stage, config)\n/app/solution/train_current_model.py:530:        save_cache(cache, prepared, stage, config)\n/app/solution/train_current_model.py:603:        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n/app/solution/train_current_model.py:609:def invalid_full_history_negatives(\n/app/solution/train_current_model.py:610:    negatives: np.ndarray,\n/app/solution/train_current_model.py:616:    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n/app/solution/train_current_model.py:617:    byte_columns = negatives >> 3\n/app/solution/train_current_model.py:618:    bit_columns = negatives & 7\n/app/solution/train_current_model.py:621:    invalid |= negatives == targets[:, None]\n/app/solution/train_current_model.py:622:    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n/app/solution/train_current_model.py:623:    for column in range(1, negatives.shape[1]):\n/app/solution/train_current_model.py:625:            negatives[:, column, None] == negatives[:, :column]\n/app/solution/train_current_model.py:630:def draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:641:    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n/app/solution/train_current_model.py:647:        (batch_size, config.uniform_negatives),\n/app/solution/train_current_model.py:653:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:656:            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n/app/solution/train_current_model.py:672:        if corrected_count < config.inbatch_negatives:\n/app/solution/train_current_model.py:675:                (batch_size, config.inbatch_negatives - corrected_count),\n/app/solution/train_current_model.py:681:    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n/app/solution/train_current_model.py:682:    correction = np.ones_like(negatives, dtype=np.float32)\n/app/solution/train_current_model.py:685:            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n/app/solution/train_current_model.py:688:        invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:689:            negatives,\n/app/solution/train_current_model.py:697:                torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:706:        negatives[invalid] = replacements\n/app/solution/train_current_model.py:709:    invalid = invalid_full_history_negatives(\n/app/solution/train_current_model.py:710:        negatives,\n/app/solution/train_current_model.py:717:        raise RuntimeError(\"full-history negative resampling failed\")\n/app/solution/train_current_model.py:719:        torch.from_numpy(negatives).to(device),\n/app/solution/train_current_model.py:724:def draw_training_negatives(\n/app/solution/train_current_model.py:736:    if config.negative_filter_scope == \"full-training-history\":\n/app/solution/train_current_model.py:738:            raise RuntimeError(\"full-history negative filter was not built\")\n/app/solution/train_current_model.py:739:        return draw_full_history_filtered_negatives(\n/app/solution/train_current_model.py:750:    return base.draw_filtered_mixed_negatives(\n/app/solution/train_current_model.py:755:        config.uniform_negatives,\n/app/solution/train_current_model.py:756:        config.inbatch_negatives,\n/app/solution/train_current_model.py:816:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:818:    all_items = torch.cat([positives, negatives.reshape(-1)])\n/app/solution/train_current_model.py:822:    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n/app/solution/train_current_model.py:823:        len(positives), negatives.shape[1], -1\n/app/solution/train_current_model.py:825:    return positive_vectors, negative_vectors\n/app/solution/train_current_model.py:845:def corrected_negative_loss(\n/app/solution/train_current_model.py:851:    total = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:853:    if config.uniform_negatives:\n/app/solution/train_current_model.py:854:        result += config.uniform_negatives * raw[\n/app/solution/train_current_model.py:855:            :, : config.uniform_negatives\n/app/solution/train_current_model.py:857:    if config.inbatch_negatives:\n/app/solution/train_current_model.py:858:        selected = slice(config.uniform_negatives, total)\n/app/solution/train_current_model.py:860:        result += config.inbatch_negatives * (\n/app/solution/train_current_model.py:880:        raise RuntimeError(\"chronological target partition produced negative counts\")\n/app/solution/train_current_model.py:915:    public: Path, stage: str, item_ids: np.ndarray\n/app/solution/train_current_model.py:918:    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n/app/solution/train_current_model.py:957:    stage: str,\n/app/solution/train_current_model.py:978:                public, stage, prepared.item_ids\n/app/solution/train_current_model.py:981:                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n/app/solution/train_current_model.py:1119:    negatives: torch.Tensor,\n/app/solution/train_current_model.py:1120:    negative_weights: torch.Tensor,\n/app/solution/train_current_model.py:1121:    sample_weights: np.ndarray,\n/app/solution/train_current_model.py:1127:    total_weight = float(sample_weights.sum())\n/app/solution/train_current_model.py:1129:        raise RuntimeError(\"target block has no positive sample weight\")\n/app/solution/train_current_model.py:1132:        \"loss_sum\": 0.0,\n/app/solution/train_current_model.py:1134:        \"negative_sum\": 0.0,\n/app/solution/train_current_model.py:1138:    for begin in range(0, target_count, config.loss_microbatch_size):\n/app/solution/train_current_model.py:1139:        end = min(begin + config.loss_microbatch_size, target_count)\n/app/solution/train_current_model.py:1162:        positive_vectors, negative_vectors = candidate_vectors(\n/app/solution/train_current_model.py:1165:            negatives[begin:end],\n/app/solution/train_current_model.py:1168:        negative_logits = torch.einsum(\n/app/solution/train_current_model.py:1169:            \"bd,bkd->bk\", query_vectors, negative_vectors\n/app/solution/train_current_model.py:1171:        positive_loss = F.softplus(-positive_logits)\n/app/solution/train_current_model.py:1172:        negative_loss = corrected_negative_loss(\n/app/solution/train_current_model.py:1173:            negative_logits, negative_weights[begin:end], config\n/app/solution/train_current_model.py:1176:            sample_weights[begin:end].astype(np.float32, copy=False)\n/app/solution/train_current_model.py:1178:        loss_sum = (\n/app/solution/train_current_model.py:1179:            selected_weights * (positive_loss + negative_loss) / 2.0\n/app/solution/train_current_model.py:1181:        if not bool(torch.isfinite(loss_sum)):\n/app/solution/train_current_model.py:1182:            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n/app/solution/train_current_model.py:1184:            (loss_sum / total_weight).backward()\n/app/solution/train_current_model.py:1188:        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n/app/solution/train_current_model.py:1190:        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n/app/solution/train_current_model.py:1192:            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n/app/solution/train_current_model.py:1227:    negative_count = config.uniform_negatives + config.inbatch_negatives\n/app/solution/train_current_model.py:1228:    total_loss = 0.0\n/app/solution/train_current_model.py:1232:    total_negative = 0.0\n/app/solution/train_current_model.py:1293:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1314:                negatives,\n/app/solution/train_current_model.py:1315:                negative_weights,\n/app/solution/train_current_model.py:1327:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1331:            total_negative += statistics[\"negative_sum\"]\n/app/solution/train_current_model.py:1337:                batch_bce = statistics[\"loss_sum\"] / max(\n/app/solution/train_current_model.py:1340:                running_bce = total_loss / max(total_weight, 1.0e-12)\n/app/solution/train_current_model.py:1351:        \"loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1353:        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1355:        / max(total_targets * negative_count, 1),\n/app/solution/train_current_model.py:1388:    total_loss = 0.0\n/app/solution/train_current_model.py:1449:            negatives, negative_weights = draw_training_negatives(\n/app/solution/train_current_model.py:1469:                negatives,\n/app/solution/train_current_model.py:1470:                negative_weights,\n/app/solution/train_current_model.py:1475:            total_loss += statistics[\"loss_sum\"]\n/app/solution/train_current_model.py:1481:        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n/app/solution/train_current_model.py:1523:    stage: str,\n/app/solution/train_current_model.py:1560:        stage,\n/app/solution/train_current_model.py:1567:        if config.negative_filter_scope == \"full-training-history\"\n/app/solution/train_current_model.py:1571:    best_loss = float(\"inf\")\n/app/solution/train_current_model.py:1601:            \"negative_filter_scope\", \"last-100\"\n/app/solution/train_current_model.py:1629:            stored_filter_scope != config.negative_filter_scope\n/app/solution/train_current_model.py:1657:            prior.pop(\"validation_loss\", None)\n/app/solution/train_current_model.py:1660:                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n/app/solution/train_current_model.py:1666:        if \"validation_loss\" not in prior:\n/app/solution/train_current_model.py:1682:        best_loss = float(prior[\"validation_loss\"])\n/app/solution/train_current_model.py:1687:            f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1731:            diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1732:            < best_loss - config.early_stopping_min_delta\n/app/solution/train_current_model.py:1735:            best_loss = diagnostics[\"validation_loss\"]\n/app/solution/train_current_model.py:1754:            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n/app/solution/train_current_model.py:1755:            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n/app/solution/train_current_model.py:1766:                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1776:        f\"loss={best_loss:.6f}\"\n/app/solution/train_current_model.py:1861:def rank_candidates(\n/app/solution/train_current_model.py:1867:    ranking_batch_size: int,\n/app/solution/train_current_model.py:1882:    for start in range(0, len(eligibility.uids), ranking_batch_size):\n/app/solution/train_current_model.py:1883:        end = min(start + ranking_batch_size, len(eligibility.uids))\n/app/solution/train_current_model.py:1896:                (uid, int(prepared.item_ids[column]), rank)\n/app/solution/train_current_model.py:1897:                for rank, column in enumerate(columns, start=1)\n/app/solution/train_current_model.py:1900:            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n/app/solution/train_current_model.py:1909:    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n/app/solution/train_current_model.py:1912:def write_ranking(frame: pd.DataFrame, output: Path) -> None:\n/app/solution/train_current_model.py:1923:    parser = argparse.ArgumentParser(description=__doc__)\n/app/solution/train_current_model.py:1925:        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n/app/solution/train_current_model.py:1939:        \"--loss-microbatch-size\",\n/app/solution/train_current_model.py:1941:        default=Config.loss_microbatch_size,\n/app/solution/train_current_model.py:1944:        \"--negative-filter-scope\",\n/app/solution/train_current_model.py:1946:        default=Config.negative_filter_scope,\n/app/solution/train_current_model.py:2003:    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n/app/solution/train_current_model.py:2012:        or args.loss_microbatch_size < 1\n/app/solution/train_current_model.py:2028:    config = Config(\n/app/solution/train_current_model.py:2033:        loss_microbatch_size=args.loss_microbatch_size,\n/app/solution/train_current_model.py:2034:        negative_filter_scope=args.negative_filter_scope,\n/app/solution/train_current_model.py:2057:        args.stage,\n/app/solution/train_current_model.py:2071:                    \"stage\": args.stage,\n/app/solution/train_current_model.py:2095:        args.stage,\n/app/solution/train_current_model.py:2102:    ranking, embedding_diagnostics = rank_candidates(\n/app/solution/train_current_model.py:2108:        args.ranking_batch_size,\n/app/solution/train_current_model.py:2110:    write_ranking(ranking, args.output.resolve())\n/app/solution/train_current_model.py:2115:                \"stage\": args.stage,\n/app/solution/train_current_model.py:2117:                \"rows\": len(ranking),\n/app/solution/train_current_model.py:2118:                \"users\": int(ranking.uid.nunique()),\n/app/solution/train_current_model.py:2126:                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n/app/solution/train_current_model.py:2129:                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n/app/solution/train_current_model.py:2135:                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n/app/solution/train_current_model.py:2136:                    \"negative_sampling\": (\n/app/solution/train_current_model.py:2139:                    \"false_negative_filter\": config.negative_filter_scope,\n    dislike_count: int,\n) -> np.ndarray:\n    start = int(\n        np.searchsorted(\n            timestamps,\n            history_end - base.PROFILE_LOOKBACK_DAYS * base.DAY,\n            side=\"left\",\n        )\n    )\n    result = np.zeros(6, dtype=np.float32)\n    recent_items = items[start:]\n    if len(recent_items):\n        result[0] = np.log1p(len(recent_items)) / 8.0\n        result[1] = np.log1p(len(np.unique(recent_items))) / 6.0\n        result[2] = float(np.mean(event_features[start:, 0]))\n        result[3] = float(np.mean(event_features[start:, 1]))\n    result[4] = np.log1p(like_count) / 6.0\n    result[5] = np.log1p(dislike_count) / 4.0\n    return result\n\n\ndef prepare_data(\n    public: Path, stage: str, config: Config\n) -> tuple[SequenceData, CandidateSet]:\n    data = public / \"data\"\n    catalog = pd.read_parquet(data / \"candidate_catalog.parquet\").sort_values(\n        \"popularity_rank\"\n    )\n    item_ids = catalog.item_id.to_numpy(dtype=np.int64, copy=True)\n    item_index = pd.Index(item_ids)\n    n_items = len(item_ids)\n    if n_items >= np.iinfo(np.uint16).max:\n        raise RuntimeError(\"uint16 item storage is too small for this catalog\")\n\n    if stage == \"validation\":\n        prefixes = (\"train\",)\n        history_end = base.TRAIN_END\n        candidate_name = \"validation_eligible_candidates.npz\"\n        state_name = \"validation_preference_state.parquet\"\n    else:\n        prefixes = (\"train\", \"val\")\n        history_end = base.VALIDATION_END\n        candidate_name = \"test_eligible_candidates.npz\"\n        state_name = \"test_preference_state.parquet\"\n    eligibility = CandidateSet.read(data / candidate_name)\n    if not np.array_equal(eligibility.item_ids, item_ids):\n        raise RuntimeError(\"catalog and candidate artifact item order differ\")\n\n    explicit_by_user = base.load_explicit_events(data, prefixes, item_index)\n    inference_likes, inference_dislikes, like_counts, dislike_counts = (\n        base.load_inference_state(\n            data / state_name,\n            item_index,\n            eligibility.uids,\n            n_items,\n        )\n    )\n    inference_rows = {int(uid): row for row, uid in enumerate(eligibility.uids)}\n    inference_user_features = np.zeros((len(eligibility.uids), 6), dtype=np.float32)\n    inference_sequence_rows = np.full(len(eligibility.uids), -1, dtype=np.int32)\n\n    # Snapshot zero is the shared empty explicit state.\n    liked_states = [np.full(base.LIKE_ITEMS, n_items, dtype=np.uint16)]\n    disliked_states = [\n        np.full(base.DISLIKE_ITEMS, n_items, dtype=np.uint16)\n    ]\n    state_counts: list[tuple[int, int]] = [(0, 0)]\n    user_ids: list[int] = []\n    offsets = [0]\n    timestamp_parts: list[np.ndarray] = []\n    item_parts: list[np.ndarray] = []\n    event_parts: list[np.ndarray] = []\n    activity_parts: list[np.ndarray] = []\n    state_parts: list[np.ndarray] = []\n\n    listen_paths = [data / f\"{prefix}_listens.parquet\" for prefix in prefixes]\n    started = time.monotonic()\n    for seen_users, (uid, listens) in enumerate(\n        base.merge_listen_streams(listen_paths, item_index), start=1\n    ):\n        parts = build_sequence_parts(\n            listens,\n            explicit_by_user.get(uid, base.empty_explicit_events()),\n            n_items,\n            liked_states,\n            disliked_states,\n            state_counts,\n        )\n        if parts is None:\n            continue\n        sequence_row = len(user_ids)\n        user_ids.append(uid)\n        timestamp_parts.append(parts[0].astype(np.uint32, copy=False))\n        item_parts.append(parts[1])\n        event_parts.append(parts[2])\n        activity_parts.append(parts[3])\n        state_parts.append(parts[4])\n        offsets.append(offsets[-1] + len(parts[1]))\n        inference_row = inference_rows.get(uid)\n        if inference_row is not None:\n            inference_sequence_rows[inference_row] = sequence_row\n            inference_user_features[inference_row] = final_user_features(\n                parts[0],\n                parts[1],\n                parts[2],\n                history_end,\n                int(like_counts[inference_row]),\n                int(dislike_counts[inference_row]),\n            )\n        if seen_users % 1_000 == 0:\n            log(\n                f\"prepared users={seen_users:,} tokens={offsets[-1]:,} \"\n                f\"states={len(liked_states):,} \"\n                f\"elapsed={time.monotonic() - started:.1f}s\"\n            )\n\n    missing = np.flatnonzero(inference_sequence_rows < 0)\n    if len(missing):\n        inference_user_features[missing, 4] = np.log1p(like_counts[missing]) / 6.0\n        inference_user_features[missing, 5] = (\n            np.log1p(dislike_counts[missing]) / 4.0\n        )\n        log(f\"target users without qualifying catalog sequence={len(missing):,}\")\n\n    prepared = SequenceData(\n        item_ids=item_ids,\n        item_features=base.build_item_features(catalog),\n        user_ids=np.asarray(user_ids, dtype=np.int64),\n        offsets=np.asarray(offsets, dtype=np.int64),\n        sequence_timestamps=np.concatenate(timestamp_parts),\n        sequence_items=np.concatenate(item_parts),\n        event_features=np.concatenate(event_parts),\n        activity_features=np.concatenate(activity_parts),\n        state_ids=np.concatenate(state_parts),\n        liked_states=np.stack(liked_states),\n        disliked_states=np.stack(disliked_states),\n        state_counts=np.asarray(state_counts, dtype=np.int32),\n        inference_user_rows=inference_sequence_rows,\n        inference_liked_items=inference_likes,\n        inference_disliked_items=inference_dislikes,\n        inference_user_features=inference_user_features,\n    )\n    log(\n        f\"prepared stage={stage} sequence_users={len(prepared.user_ids):,} \"\n        f\"tokens={len(prepared.sequence_items):,} \"\n        f\"next_item_targets={prepared.target_count:,} \"\n        f\"states={len(prepared.liked_states):,}\"\n    )\n    return prepared, eligibility\n\n\ndef cache_metadata(stage: str, config: Config) -> dict[str, object]:\n    return {\n        \"cache_version\": CACHE_VERSION,\n        \"stage\": stage,\n        \"positive_listen_threshold\": base.LISTEN_POSITIVE_THRESHOLD,\n        \"profile_lookback_days\": base.PROFILE_LOOKBACK_DAYS,\n        \"event_time_feature\": \"exp-negative-gap-over-60-days\",\n    }\n\n\ndef save_cache(\n    path: Path, prepared: SequenceData, stage: str, config: Config\n) -> None:\n    path.parent.mkdir(parents=True, exist_ok=True)\n    np.savez(\n        path,\n        metadata=np.asarray(json.dumps(cache_metadata(stage, config), sort_keys=True)),\n        **prepared.__dict__,\n    )\n    log(f\"saved public-derived full-sequence cache: {path}\")\n\n\ndef load_cache(path: Path, stage: str, config: Config) -> SequenceData:\n    with np.load(path, allow_pickle=False) as artifact:\n        actual = json.loads(str(artifact[\"metadata\"].item()))\n        expected = cache_metadata(stage, config)\n        if actual != expected:\n            raise RuntimeError(f\"sequence cache differs: {actual} != {expected}\")\n        values = {\n            field: artifact[field].copy()\n            for field in SequenceData.__dataclass_fields__\n        }\n    prepared = SequenceData(**values)\n    log(\n        f\"loaded full-sequence cache: tokens={len(prepared.sequence_items):,} \"\n        f\"targets={prepared.target_count:,}\"\n    )\n    return prepared\n\n\ndef load_or_prepare(\n    public: Path,\n    stage: str,\n    config: Config,\n    cache: Path | None,\n) -> tuple[SequenceData, CandidateSet]:\n    candidate_name = (\n        \"validation_eligible_candidates.npz\"\n        if stage == \"validation\"\n        else \"test_eligible_candidates.npz\"\n    )\n    eligibility = CandidateSet.read(public / \"data\" / candidate_name)\n    if cache is not None and cache.is_file():\n        prepared = load_cache(cache, stage, config)\n        if not np.array_equal(prepared.item_ids, eligibility.item_ids):\n            raise RuntimeError(\"cached catalog differs from candidate artifact\")\n        return prepared, eligibility\n    prepared, built_eligibility = prepare_data(public, stage, config)\n    if cache is not None:\n        save_cache(cache, prepared, stage, config)\n    return prepared, built_eligibility\n\n\ndef build_item_correction(\n    prepared: SequenceData,\n    config: Config,\n    target_starts: np.ndarray,\n    target_counts: np.ndarray,\n) -> torch.Tensor:\n    \"\"\"Estimate in-batch propensities from the selected training targets.\"\"\"\n    counts = np.zeros(len(prepared.item_ids), dtype=np.float64)\n    for user_row, count in enumerate(target_counts):\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        target_start = int(target_starts[user_row])\n        counts += np.bincount(\n            prepared.sequence_items[\n                offset\n                + target_start\n                + 1 : offset\n                + target_start\n                + int(count)\n                + 1\n            ].astype(np.int64),\n            minlength=len(prepared.item_ids),\n        )\n    total = float(counts.sum())\n    probabilities = (counts + 1.0) / (total + len(counts))\n    raw = np.power(\n        (1.0 / len(counts)) / probabilities,\n        config.inbatch_correction_power,\n    )\n    normalization = float(np.sum(counts * raw) / max(total, 1.0))\n    correction = np.clip(\n        raw / max(normalization, 1.0e-12),\n        config.inbatch_correction_min,\n        config.inbatch_correction_max,\n    ).astype(np.float32)\n    mean_on_targets = float(np.sum(counts * correction) / max(total, 1.0))\n    log(\n        f\"inbatch correction: min={correction.min():.3f} \"\n        f\"mean_on_targets={mean_on_targets:.3f} max={correction.max():.3f}\"\n    )\n    return torch.from_numpy(correction)\n\n\ndef build_known_positive_filter(\n    prepared: SequenceData, training_counts: np.ndarray\n) -> np.ndarray:\n    \"\"\"Pack each user's complete public-training positive-item set.\"\"\"\n    width = (len(prepared.item_ids) + 7) // 8\n    packed = np.zeros((len(prepared.user_ids), width), dtype=np.uint8)\n    retained = 0\n    for user_row, target_count in enumerate(training_counts):\n        if not target_count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        # T adjacent targets consume sequence positions 0 through T.  The\n        # chronological BCE suffix starts at T + 1 and is intentionally absent.\n        items = np.unique(\n            prepared.sequence_items[\n                offset : offset + int(target_count) + 1\n            ].astype(np.int64)\n        )\n        byte_columns = items >> 3\n        bit_values = np.left_shift(\n            np.uint8(1), (items & 7).astype(np.uint8)\n        )\n        np.bitwise_or.at(packed[user_row], byte_columns, bit_values)\n        retained += len(items)\n    log(\n        f\"full-history false-negative filter: users={len(prepared.user_ids):,} \"\n        f\"unique_user_items={retained:,} bytes={packed.nbytes:,}\"\n    )\n    return packed\n\n\ndef invalid_full_history_negatives(\n    negatives: np.ndarray,\n    targets: np.ndarray,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray,\n    liked_items: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return row-level invalid negatives using the complete training prefix.\"\"\"\n    byte_columns = negatives >> 3\n    bit_columns = negatives & 7\n    known = known_positive_packed[user_rows[:, None], byte_columns]\n    invalid = ((known >> bit_columns) & 1).astype(bool)\n    invalid |= negatives == targets[:, None]\n    invalid |= (negatives[:, :, None] == liked_items[:, None, :]).any(axis=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= (\n            negatives[:, column, None] == negatives[:, :column]\n        ).any(axis=1)\n    return invalid\n\n\ndef draw_full_history_filtered_negatives(\n    targets: torch.Tensor,\n    user_rows: np.ndarray,\n    liked_items: torch.Tensor,\n    known_positive_packed: np.ndarray,\n    n_items: int,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n    targets_cpu = targets.detach().cpu().numpy().astype(np.int64, copy=False)\n    liked_cpu = liked_items.detach().cpu().numpy().astype(np.int64, copy=False)\n    batch_size = len(targets_cpu)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, config.uniform_negatives),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n    corrected_count = 0\n    if config.inbatch_negatives:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(\n            config.inbatch_negatives, max(len(unique_targets) - 1, 0)\n        )\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(\n                    torch.from_numpy(targets_cpu)[:, None]\n                ),\n                -1.0,\n            )\n            columns = torch.topk(\n                priorities, k=corrected_count, dim=1\n            ).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < config.inbatch_negatives:\n            filler = torch.randint(\n                n_items,\n                (batch_size, config.inbatch_negatives - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives = torch.cat([uniform, inbatch], dim=1).numpy()\n    correction = np.ones_like(negatives, dtype=np.float32)\n    if corrected_count:\n        correction[\n            :, config.uniform_negatives : config.uniform_negatives + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]].numpy()\n    for _ in range(32):\n        invalid = invalid_full_history_negatives(\n            negatives,\n            targets_cpu,\n            user_rows,\n            known_positive_packed,\n            liked_cpu,\n        )\n        if not np.any(invalid):\n            return (\n                torch.from_numpy(negatives).to(device),\n                torch.from_numpy(correction).to(device),\n            )\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum()),),\n            generator=generator,\n            device=\"cpu\",\n        ).numpy()\n        negatives[invalid] = replacements\n        # Rejected in-batch items become ordinary uniform draws.\n        correction[invalid] = 1.0\n    invalid = invalid_full_history_negatives(\n        negatives,\n        targets_cpu,\n        user_rows,\n        known_positive_packed,\n        liked_cpu,\n    )\n    if np.any(invalid):\n        raise RuntimeError(\"full-history negative resampling failed\")\n    return (\n        torch.from_numpy(negatives).to(device),\n        torch.from_numpy(correction).to(device),\n    )\n\n\ndef draw_training_negatives(\n    positive_items: torch.Tensor,\n    known_history: torch.Tensor,\n    liked_items: torch.Tensor,\n    user_rows: np.ndarray,\n    known_positive_packed: np.ndarray | None,\n    prepared: SequenceData,\n    config: Config,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    if config.negative_filter_scope == \"full-training-history\":\n        if known_positive_packed is None:\n            raise RuntimeError(\"full-history negative filter was not built\")\n        return draw_full_history_filtered_negatives(\n            positive_items,\n            user_rows,\n            liked_items,\n            known_positive_packed,\n            len(prepared.item_ids),\n            config,\n            item_correction,\n            generator,\n            device,\n        )\n    return base.draw_filtered_mixed_negatives(\n        positive_items,\n        known_history,\n        liked_items,\n        len(prepared.item_ids),\n        config.uniform_negatives,\n        config.inbatch_negatives,\n        item_correction,\n        generator,\n        device,\n    )\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_1, config.item_hidden_2),\n            nn.GELU(),\n            nn.Dropout(config.dropout),\n            nn.Linear(config.item_hidden_2, dim),\n        )\n        nn.init.normal_(self.context_embedding.weight, std=0.02)\n        nn.init.normal_(self.candidate_embedding.weight, std=0.02)\n        with torch.no_grad():\n            self.context_embedding.weight[n_items].zero_()\n\n    def _mean_context_channel(self, items: torch.Tensor) -> torch.Tensor:\n        mask = items.ne(self.n_items)\n        vectors = self.context_embedding(items)\n        return (vectors * mask.unsqueeze(-1)).sum(dim=1) / mask.sum(\n            dim=1, keepdim=True\n        ).clamp_min(1)\n\n    def encode_items(self, items: torch.Tensor) -> torch.Tensor:\n        inputs = torch.cat(\n            [self.candidate_embedding(items), self.item_features[items]], dim=1\n        )\n        return self.item_tower(inputs)\n\n\ndef invalid_negative_mask(\n    negatives: torch.Tensor,\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n) -> torch.Tensor:\n    \"\"\"Identify targets, known positives, active likes, and row duplicates.\"\"\"\n    invalid = negatives.eq(targets[:, None])\n    invalid |= negatives[:, :, None].eq(context_items[:, None, :]).any(dim=2)\n    invalid |= negatives[:, :, None].eq(liked_items[:, None, :]).any(dim=2)\n    for column in range(1, negatives.shape[1]):\n        invalid[:, column] |= negatives[:, column, None].eq(\n            negatives[:, :column]\n        ).any(dim=1)\n    return invalid\n\n\ndef draw_filtered_mixed_negatives(\n    targets: torch.Tensor,\n    context_items: torch.Tensor,\n    liked_items: torch.Tensor,\n    n_items: int,\n    uniform_count: int,\n    inbatch_count: int,\n    item_correction: torch.Tensor,\n    generator: torch.Generator,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    \"\"\"Draw uniform and unique-target in-batch negatives.\"\"\"\n    batch_size = len(targets)\n    uniform = torch.randint(\n        n_items,\n        (batch_size, uniform_count),\n        generator=generator,\n        device=\"cpu\",\n    )\n    inbatch = torch.empty((batch_size, 0), dtype=torch.long, device=\"cpu\")\n    corrected_count = 0\n    if inbatch_count:\n        unique_targets = torch.unique(targets.detach().cpu())\n        corrected_count = min(inbatch_count, max(len(unique_targets) - 1, 0))\n        if corrected_count:\n            priorities = torch.rand(\n                (batch_size, len(unique_targets)), generator=generator\n            )\n            priorities.masked_fill_(\n                unique_targets[None, :].eq(targets.detach().cpu()[:, None]),\n                -1.0,\n            )\n            columns = torch.topk(priorities, k=corrected_count, dim=1).indices\n            inbatch = unique_targets[columns]\n        if corrected_count < inbatch_count:\n            filler = torch.randint(\n                n_items,\n                (batch_size, inbatch_count - corrected_count),\n                generator=generator,\n                device=\"cpu\",\n            )\n            inbatch = torch.cat([inbatch, filler], dim=1)\n\n    negatives_cpu = torch.cat([uniform, inbatch], dim=1)\n    correction_cpu = torch.ones_like(negatives_cpu, dtype=torch.float32)\n    if corrected_count:\n        correction_cpu[\n            :, uniform_count : uniform_count + corrected_count\n        ] = item_correction[inbatch[:, :corrected_count]]\n    negatives = negatives_cpu.to(device)\n    correction = correction_cpu.to(device)\n    for _ in range(32):\n        invalid = invalid_negative_mask(\n            negatives, targets, context_items, liked_items\n        )\n        if not bool(invalid.any()):\n            return negatives, correction\n        replacements = torch.randint(\n            n_items,\n            (int(invalid.sum().detach().cpu()),),\n            generator=generator,\n            device=\"cpu\",\n        ).to(device)\n        negatives[invalid] = replacements\n        correction[invalid] = 1.0\n    invalid = invalid_negative_mask(\n        negatives, targets, context_items, liked_items\n    )\n    if bool(invalid.any()):\n        raise RuntimeError(\"mixed negative resampling failed false-negative filter\")\n    return negatives, correction\n"
            }
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:39:59.945Z",
          "data": {
            "type": "token_usage_record",
            "thread_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "session_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "response_id": "resp_038c43f9aa686cae016ab4472a90ec87d2bbedb6edc9ce12ff",
            "usage": {
              "input_tokens": 20138,
              "cached_input_tokens": 14720,
              "cache_write_input_tokens": 0,
              "output_tokens": 135,
              "reasoning_output_tokens": 8,
              "total_tokens": 20273
            },
            "turn_token_usage": {
              "input_tokens": 35038,
              "cached_input_tokens": 25856,
              "cache_write_input_tokens": 0,
              "output_tokens": 362,
              "reasoning_output_tokens": 31,
              "total_tokens": 35400
            },
            "thread_token_usage": {
              "input_tokens": 35038,
              "cached_input_tokens": 25856,
              "cache_write_input_tokens": 0,
              "output_tokens": 362,
              "reasoning_output_tokens": 31,
              "total_tokens": 35400
            }
          }
        }
      ]
    },
    {
      "id": 9,
      "role": "agent",
      "timestamp": "2026-09-23T21:40:02.596Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:40:02.596Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:40:05.621Z",
          "callId": "call_Z5aQzx3fJyRKS9aWn52DpioS",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"sed -n '760,1185p' /app/solution/train_current_model.py && sed -n '1185,1785p' /app/solution/train_current_model.py && sed -n '1860,2160p' /app/solution/train_current_model.py\",workdir:\"/app\",yield_time_ms:10000,max_output_tokens:50000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:40:05.681Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\nWarning: truncated output (original token count: 12540)\nTotal output lines: 1328\n\n    )\n\n\ndef event_sequence(\n    model: base.SequentialTwoTower,\n    items: torch.Tensor,\n    features: torch.Tensor,\n    hidden: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    inputs = torch.cat([model.context_embedding(items), features], dim=-1)\n    projected = model.event_projection(inputs)\n    return model.sequence_encoder(projected, hidden)\n\n\ndef pool_explicit_states(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    state_ids: np.ndarray,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:\n    unique_states, inverse = np.unique(state_ids, return_inverse=True)\n    liked_items = torch.from_numpy(\n        prepared.liked_states[unique_states].astype(np.int64)\n    ).to(device)\n    disliked_items = torch.from_numpy(\n        prepared.disliked_states[unique_states].astype(np.int64)\n    ).to(device)\n    liked_vectors = model._mean_context_channel(liked_items)\n    disliked_vectors = model._mean_context_channel(disliked_items)\n    inverse_rows = torch.from_numpy(inverse.astype(np.int64)).to(device)\n    counts = prepared.state_counts[state_ids]\n    return (\n        liked_vectors[inverse_rows],\n        disliked_vectors[inverse_rows],\n        torch.from_numpy(counts.astype(np.float32)).to(device),\n    )\n\n\ndef user_queries(\n    model: base.SequentialTwoTower,\n    sequence_vectors: torch.Tensor,\n    liked_vectors: torch.Tensor,\n    disliked_vectors: torch.Tensor,\n    user_features: torch.Tensor,\n) -> torch.Tensor:\n    return model.user_tower(\n        torch.cat(\n            [sequence_vectors, liked_vectors, disliked_vectors, user_features],\n            dim=1,\n        )\n    )\n\n\ndef candidate_vectors(\n    model: base.SequentialTwoTower,\n    positives: torch.Tensor,\n    negatives: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    all_items = torch.cat([positives, negatives.reshape(-1)])\n    unique_items, inverse = torch.unique(all_items, return_inverse=True)\n    encoded = model.encode_items(unique_items)\n    positive_vectors = encoded[inverse[: len(positives)]]\n    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n        len(positives), negatives.shape[1], -1\n    )\n    return positive_vectors, negative_vectors\n\n\ndef history_windows(\n    sequence: np.ndarray,\n    start: int,\n    count: int,\n    width: int,\n    padding_item: int,\n) -> np.ndarray:\n    base_start = max(0, start - width + 1)\n    segment = sequence[base_start : start + count]\n    padded = np.concatenate(\n        [np.full(width - 1, padding_item, dtype=np.uint16), segment]\n    )\n    windows = np.lib.stride_tricks.sliding_window_view(padded, width)\n    offset = start - base_start\n    return windows[offset : offset + count].copy()\n\n\ndef corrected_negative_loss(\n    logits: torch.Tensor,\n    correction: torch.Tensor,\n    config: Config,\n) -> torch.Tensor:\n    raw = F.softplus(logits)\n    total = config.uniform_negatives + config.inbatch_negatives\n    result = torch.zeros(len(logits), device=logits.device)\n    if config.uniform_negatives:\n        result += config.uniform_negatives * raw[\n            :, : config.uniform_negatives\n        ].mean(dim=1)\n    if config.inbatch_negatives:\n        selected = slice(config.uniform_negatives, total)\n        weights = correction[:, selected]\n        result += config.inbatch_negatives * (\n            (raw[:, selected] * weights).sum(dim=1)\n            / weights.sum(dim=1).clamp_min(1.0e-6)\n        )\n    return result / total\n\n\ndef retained_target_window_starts(\n    total_targets: np.ndarray,\n    validation_counts: np.ndarray,\n    training_counts: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return the discarded prefix before the retained chronological suffix.\"\"\"\n    training_region_ends = total_targets - validation_counts\n    window_starts = training_region_ends - training_counts\n    if (\n        np.any(window_starts < 0)\n        or np.any(training_counts < 0)\n        or np.any(validation_counts < 0)\n    ):\n        raise RuntimeError(\"chronological target partition produced negative counts\")\n    if not np.array_equal(\n        window_starts + training_counts + validation_counts, total_targets\n    ):\n        raise RuntimeError(\"chronological target window is not a final contiguous suffix\")\n    return window_starts\n\n\ndef chronological_target_partition(\n    prepared: SequenceData,\n    validation_fraction: float,\n    max_train_targets_per_user: int,\n    max_validation_targets_per_user: int,\n) -> TargetPartition:\n    \"\"\"Select a recent contiguous window with a final out-of-time BCE suffix.\"\"\"\n    totals = np.maximum(prepared.lengths - 1, 0).astype(np.int64)\n    validation = np.floor(totals * validation_fraction).astype(np.int64)\n    validation[(totals >= 2) & (validation == 0)] = 1\n    if max_validation_targets_per_user:\n        validation = np.minimum(validation, max_validation_targets_per_user)\n\n    history_training = totals - validation\n    training = history_training.copy()\n    if max_train_targets_per_user:\n        training = np.minimum(training, max_train_targets_per_user)\n    window_starts = retained_target_window_starts(totals, validation, training)\n    return TargetPartition(\n        window_starts=window_starts,\n        training_counts=training,\n        validation_counts=validation,\n        history_training_counts=history_training,\n    )\n\n\ndef load_organic_like_outcomes(\n    public: Path, stage: str, item_ids: np.ndarray\n) -> dict[int, dict[int, np.ndarray]]:\n    \"\"\"Load mapped organic-like timestamps from public fitting history.\"\"\"\n    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n    frames = [\n        pd.read_parquet(\n            public / \"data\" / f\"{prefix}_likes.parquet\",\n            columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n        )\n        for prefix in prefixes\n    ]\n    likes = pd.concat(frames, ignore_index=True)\n    likes = likes[likes.is_organic == 1].copy()\n    mapped = pd.Index(item_ids).get_indexer(\n        likes.item_id.to_numpy(dtype=np.int64)\n    )\n    likes = likes.loc[mapped >= 0, [\"uid\", \"timestamp\"]].copy()\n    likes[\"item\"] = mapped[mapped >= 0].astype(np.int32, copy=False)\n    likes = likes.sort_values([\"uid\", \"item\", \"timestamp\"], kind=\"stable\")\n    nested: dict[int, dict[int, list[int]]] = {}\n    for raw_uid, raw_timestamp, raw_item in likes.itertuples(\n        index=False, name=None\n    ):\n        nested.setdefault(int(raw_uid), {}).setdefault(int(raw_item), []).append(\n            int(raw_timestamp)\n        )\n    result = {\n        uid: {\n            item: np.asarray(timestamps, dtype=np.int64)\n            for item, timestamps in items.items()\n        }\n        for uid, items in nested.items()\n    }\n    log(\n        f\"loaded organic-like outcomes: rows={len(likes):,} \"\n        f\"users={len(result):,}\"\n    )\n    return result\n\n\ndef build_target_weights(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    training_counts: np.ndarray,\n    config: Config,\n) -> np.ndarray:\n    \"\"\"Build nonzero per-token weights without dropping adjacent targets.\"\"\"\n    if config.target_weighting == \"uniform\":\n        weights = np.ones(len(prepared.sequence_items), dtype=np.float32)\n    else:\n        weights = np.full(\n            len(prepared.sequence_items),\n            config.ordinary_target_weight,\n            dtype=np.float32,\n        )\n        organic_strong = (\n            (prepared.event_features[:, 0] > 0.5)\n            & (prepared.event_features[:, 1] >= 0.8)\n        )\n        weights[organic_strong] = config.organic_strong_target_weight\n        if config.target_weighting == \"discovery-graded\":\n            like_outcomes = load_organic_like_outcomes(\n                public, stage, prepared.item_ids\n            )\n            history_end = (\n                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n            )\n            horizon = config.discovery_horizon_days * base.DAY\n            grade_three = 0\n            for user_row, uid in enumerate(prepared.user_ids):\n                start = int(prepared.offsets[user_row])\n                end = int(prepared.offsets[user_row + 1])\n                if end - start < 2:\n                    continue\n                last_training_target = start + int(training_counts[user_row])\n                first_validation_target = last_training_target + 1\n                split_timestamp = (\n                    int(prepared.sequence_timestamps[first_validation_target])\n                    if first_validation_target < end\n                    else history_end\n                )\n                user_likes = like_outcomes.get(int(uid), {})\n                seen = {int(prepared.sequence_items[start])}\n                for position in range(start + 1, end):\n                    item = int(prepared.sequence_items[position])\n                    novel = item not in seen\n                    seen.add(item)\n                    if not novel:\n                        # Repeats remain training examples, but they cannot be\n                        # eligible discovery outcomes at the corresponding\n                        # cutoff and therefore keep only the ordinary weight.\n                        weights[position] = config.ordinary_target_weight\n                        continue\n                    timestamps = user_likes.get(item)\n                    if timestamps is None:\n                        continue\n                    timestamp = int(prepared.sequence_timestamps[position])\n                    upper = min(\n                        timestamp + horizon,\n                        split_timestamp\n                        if position <= last_training_target\n                        else history_end,\n                    )\n                    outcome = int(np.searchsorted(timestamps, timestamp, side=\"left\"))\n                    if outcome < len(timestamps) and int(timestamps[outcome]) < upper:\n                        weights[position] = config.organic_like_target_weight\n                        grade_three += 1\n            log(\n                f\"grade-3 first-encounter targets={grade_three:,} \"\n                f\"horizon_days={config.discovery_horizon_days}\"\n            )\n    log(\n        f\"target weighting={config.target_weighting} \"\n        f\"min={weights.min():.3f} mean={weights.mean():.3f} \"\n        f\"max={weights.max():.3f}\"\n    )\n    return weights\n\n\ndef build_dense_block(\n    prepared: SequenceData,\n    target_weights: np.ndarray,\n    users: np.ndarray,\n    window_starts: np.ndarray,\n    process_counts: np.ndarray,\n    score_starts: np.ndarray,\n    start: int,\n    steps: int,\n    config: Config,\n) -> tuple[np.ndarray, ...]:\n    \"\"\"Build one causal sequence block and mark the target rows to score.\"\"\"\n    batch_size = len(users)\n    padding_item = len(prepared.item_ids)\n    input_items = np.full((batch_size, steps), padding_item, dtype=np.uint16)\n    event_features = np.zeros((batch_size, steps, 3), dtype=np.float16)\n    activity_features = np.zeros((batch_size, steps, 4), dtype=np.float16)\n    state_ids = np.zeros((batch_size, steps), dtype=np.uint32)\n    targets = np.zeros((batch_size, steps), dtype=np.uint16)\n    weights = np.ones((batch_size, steps), dtype=np.float32)\n    scored = np.zeros((batch_size, steps), dtype=bool)\n    histories = np.full(\n        (batch_size, steps, config.bptt_steps),\n        padding_item,\n        dtype=np.uint16,\n    )\n    processed = np.zeros(batch_size, dtype=np.int32)\n\n    lengths = prepared.lengths\n    for row, user_row in enumerate(users):\n        count = min(steps, max(int(process_counts[row]) - start, 0))\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        window_start = int(window_starts[row])\n        absolute_start = window_start + start\n        positions = slice(\n            offset + absolute_start,\n            offset + absolute_start + count,\n        )\n        target_positions = slice(\n            offset + absolute_start + 1,\n            offset + absolute_start + count + 1,\n        )\n        input_items[row, :count] = prepared.sequence_items[positions]\n        event_features[row, :count] = prepared.event_features[positions]\n        activity_features[row, :count] = prepared.activity_features[positions]\n        state_ids[row, :count] = prepared.state_ids[positions]\n        targets[row, :count] = prepared.sequence_items[target_positions]\n        weights[row, :count] = target_weights[target_positions]\n        score_from = min(count, max(int(score_starts[row]) - start, 0))\n        scored[row, score_from:count] = True\n        processed[row] = count\n        user_sequence = prepared.sequence_items[\n            offset : offset + int(lengths[user_row])\n        ]\n        histories[row, :count] = history_windows(\n            user_sequence,\n            absolute_start,\n            count,\n            config.bptt_steps,\n            padding_item,\n        )\n    return (\n        input_items,\n        event_features,\n        activity_features,\n        state_ids,\n        targets,\n        scored,\n        histories,\n        processed,\n        weights,\n    )\n\n\ndef score_target_microbatches(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    sequence_vectors: torch.Tensor,\n    flat_states: np.ndarray,\n    flat_activity: np.ndarray,\n    positive_items: torch.Tensor,\n    negatives: torch.Tensor,\n    negative_weights: torch.Tensor,\n    sample_weights: np.ndarray,\n    device: torch.device,\n    backward: bool,\n) -> tuple[dict[str, float], torch.Tensor | None]:\n    \"\"\"Compute one logical block's exact BCE in bounded-memory slices.\"\"\"\n    target_count = len(positive_items)\n    total_weight = float(sample_weights.sum())\n    if total_weight <= 0:\n        raise RuntimeError(\"target block has no positive sample weight\")\n    sequence_gradient = torch.zeros_like(sequence_vectors) if backward else None\n    statistics = {\n        \"loss_sum\": 0.0,\n        \"positive_sum\": 0.0,\n        \"negative_sum\": 0.0,\n        \"pair_correct\": 0.0,\n        \"weight_sum\": 0.0,\n    }\n    for begin in range(0, target_count, config.loss_microbatch_size):\n        end = min(begin + config.loss_microbatch_size, target_count)\n        selected_states = flat_states[begin:end]\n        if backward:\n            sequence_input = (\n                sequence_vectors[begin:end].detach().requires_grad_(True)\n            )\n        else:\n            sequence_input = sequence_vectors[begin:end]\n        liked_vectors, disliked_vectors, _ = pool_explicit_states(\n            model, prepared, selected_states, device\n        )\n        counts = prepared.state_counts[selected_states]\n        numeric = np.zeros((end - begin, 6), dtype=np.float32)\n        numeric[:, :4] = flat_activity[begin:end]\n        numeric[:, 4] = np.log1p(counts[:, 0]) / 6.0\n        numeric[:, 5] = np.log1p(counts[:, 1]) / 4.0\n        query_vectors = user_queries(\n            model,\n            sequence_input,\n            liked_vectors,\n            disliked_vectors,\n            torch.from_numpy(numeric).to(device),\n        )\n        positive_vectors, negative_vectors = candidate_vectors(\n            model,\n            positive_items[begin:end],\n            negatives[begin:end],\n        )\n        positive_logits = (query_vectors * positive_vectors).sum(dim=1)\n        negative_logits = torch.einsum(\n            \"bd,bkd->bk\", query_vectors, negative_vectors\n        )\n        positive_loss = F.softplus(-positive_logits)\n        negative_loss = corrected_negative_loss(\n            negative_logits, negative_weights[begin:end], config\n        )\n        selected_weights = torch.from_numpy(\n            sample_weights[begin:end].astype(np.float32, copy=False)\n        ).to(device)\n        loss_sum = (\n            selected_weights * (positive_loss + negative_loss) / 2.0\n        ).sum()\n        if not bool(torch.isfinite(loss_sum)):\n            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n        if backward:\n            (loss_sum / total_weight).backward()\n            if sequence_input.grad is None:\n            if sequence_input.grad is None:\n                raise RuntimeError(\"sequence microbatch did not produce a gradient\")\n            sequence_gradient[begin:end] = sequence_input.grad\n        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n        statistics[\"positive_sum\"] += float(positive_logits.detach().sum().cpu())\n        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n        statistics[\"pair_correct\"] += float(\n            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n        )\n        statistics[\"weight_sum\"] += float(selected_weights.sum().detach().cpu())\n    return statistics, sequence_gradient\n\n\ndef release_accelerator_cache(device: torch.device) -> None:\n    if device.type == \"mps\":\n        torch.mps.empty_cache()\n\n\ndef run_training_epoch(\n    model: base.SequentialTwoTower,\n    optimizer: torch.optim.Optimizer,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    target_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    generator: torch.Generator,\n    device: torch.device,\n    epoch: int,\n) -> dict[str, float]:\n    model.train()\n    train_users = np.flatnonzero(target_counts > 0)\n    sorted_users = train_users[\n        np.argsort(target_counts[train_users], kind=\"stable\")\n    ]\n    groups = [\n        sorted_users[start : start + config.user_batch_size]\n        for start in range(0, len(sorted_users), config.user_batch_size)\n    ]\n    group_order = torch.randperm(len(groups), generator=generator).numpy()\n    negative_count = config.uniform_negatives + config.inbatch_negatives\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    total_positive = 0.0\n    total_negative = 0.0\n    total_pair_correct = 0.0\n    batches = 0\n    started = time.monotonic()\n\n    for group_number in group_order:\n        users = groups[int(group_number)]\n        group_counts = target_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_counts.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_counts,\n                np.zeros(len(users), dtype=np.int64),\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n …2540 tokens truncated…\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n            stored_config.get(\"max_validation_targets_per_user\", 0),\n        )\n        current_window_values = (\n            config.validation_fraction,\n            config.max_train_targets_per_user,\n            config.max_validation_targets_per_user,\n        )\n        objective_changed = (\n            stored_filter_scope != config.negative_filter_scope\n            or stored_target_weighting != config.target_weighting\n            or stored_weight_values != current_weight_values\n            or stored_window_values != current_window_values\n        )\n        model.load_state_dict(payload[\"model_state\"])\n        if \"optimizer_state\" in payload and not objective_changed:\n            optimizer.load_state_dict(payload[\"optimizer_state\"])\n            for group in optimizer.param_groups:\n                group[\"lr\"] = config.learning_rate\n                group[\"weight_decay\"] = config.weight_decay\n            log(f\"restored optimizer state from {resume_checkpoint}\")\n        else:\n            log(\n                f\"using a fresh AdamW optimizer after loading {resume_checkpoint}\"\n            )\n        if \"generator_state\" in payload and not objective_changed:\n            generator.set_state(payload[\"generator_state\"])\n        start_epoch = int(payload[\"epoch\"])\n        if start_epoch >= config.epochs:\n            raise RuntimeError(\n                f\"resume epoch {start_epoch} must be below --epochs {config.epochs}\"\n            )\n        prior = {\n            str(name): float(value)\n            for name, value in payload.get(\"diagnostics\", {}).items()\n        }\n        if objective_changed:\n            prior.pop(\"validation_loss\", None)\n            log(\n                \"BCE objective changed: filter \"\n                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n                \"target weighting \"\n                f\"{stored_target_weighting}->{config.target_weighting}, \"\n                f\"target window {stored_window_values}->{current_window_values}; \"\n                \"recomputing the resume checkpoint's validation BCE\"\n            )\n        if \"validation_loss\" not in prior:\n            prior.update(\n                evaluate_validation_bce(\n                    model,\n                    prepared,\n                    config,\n                    target_weights,\n                    partition.window_starts,\n                    training_counts,\n                    validation_counts,\n                    item_correction,\n                    known_positive_packed,\n                    device,\n                )\n            )\n        history.append(prior)\n        best_loss = float(prior[\"validation_loss\"])\n        best_epoch = start_epoch\n        best_state = snapshot_model(model)\n        log(\n            f\"resumed validation-BCE training: epoch={start_epoch} \"\n            f\"loss={best_loss:.6f}\"\n        )\n\n    for epoch in range(start_epoch + 1, config.epochs + 1):\n        diagnostics = run_training_epoch(\n            model,\n            optimizer,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            item_correction,\n            known_positive_packed,\n            generator,\n            device,\n            epoch,\n        )\n        validation = evaluate_validation_bce(\n            model,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            validation_counts,\n            item_correction,\n            known_positive_packed,\n            device,\n        )\n        diagnostics.update(validation)\n        history.append(diagnostics)\n        current_state = snapshot_model(model)\n        if checkpoint_dir is not None:\n            save_epoch_checkpoint(\n                checkpoint_dir,\n                epoch,\n                current_state,\n                config,\n                diagnostics,\n                optimizer,\n                generator,\n            )\n        improved = (\n            diagnostics[\"validation_loss\"]\n            < best_loss - config.early_stopping_min_delta\n        )\n        if improved:\n            best_loss = diagnostics[\"validation_loss\"]\n            best_epoch = epoch\n            best_state = current_state\n            epochs_without_improvement = 0\n            if checkpoint_dir is not None:\n                torch.save(\n                    {\n                        \"epoch\": epoch,\n                        \"config\": asdict(config),\n                        \"diagnostics\": diagnostics,\n                        \"model_state\": current_state,\n                        \"optimizer_state\": optimizer.state_dict(),\n                        \"generator_state\": generator.get_state(),\n                    },\n                    checkpoint_dir / \"best.pt\",\n                )\n        else:\n            epochs_without_improvement += 1\n        log(\n            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n            f\"pair_accuracy={diagnostics['pair_accuracy']:.3f} \"\n            f\"train_targets={int(diagnostics['targets']):,} \"\n            f\"validation_targets={int(diagnostics['validation_targets']):,} \"\n            f\"train_seconds={diagnostics['seconds']:.1f} \"\n            f\"validation_seconds={diagnostics['validation_seconds']:.1f}\"\n        )\n        release_accelerator_cache(device)\n        if epochs_without_improvement >= config.early_stopping_patience:\n            log(\n                f\"early stopping after epoch={epoch}; \"\n                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n            )\n            break\n\n    if best_state is None:\n        raise RuntimeError(\"training did not produce a valid checkpoint\")\n    model.load_state_dict(best_state)\n    model.to(device).eval()\n    log(\n        f\"restored best validation-BCE checkpoint: epoch={best_epoch} \"\n        f\"loss={best_loss:.6f}\"\n    )\n    return model, history\n\n\n@torch.inference_mode()\ndef inference_queries(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n    device: torch.device,\n    ranking_batch_size: int,\n) -> tuple[pd.DataFrame, dict[str, float]]:\n    model.eval()\n    queries = inference_queries(model, prepared, config, device)\n    item_parts: list[torch.Tensor] = []\n    for start in range(0, len(prepared.item_ids), 2_048):\n        rows = torch.arange(\n            start,\n            min(start + 2_048, len(prepared.item_ids)),\n            dtype=torch.long,\n            device=device,\n        )\n        item_parts.append(model.encode_items(rows).cpu())\n    items = torch.cat(item_parts)\n    rows: list[tuple[int, int, int]] = []\n    for start in range(0, len(eligibility.uids), ranking_batch_size):\n        end = min(start + ranking_batch_size, len(eligibility.uids))\n        scores = queries[start:end] @ items.T\n        eligible = np.unpackbits(\n            eligibility.packed[start:end],\n            axis=1,\n            count=len(prepared.item_ids),\n            bitorder=\"little\",\n        ).astype(bool, copy=False)\n        scores.masked_fill_(~torch.from_numpy(eligible), -torch.inf)\n        selected = torch.topk(scores, k=base.TOP_N, dim=1).indices.numpy()\n        for local_row, columns in enumerate(selected):\n            uid = int(eligibility.uids[start + local_row])\n            rows.extend(\n                (uid, int(prepared.item_ids[column]), rank)\n                for rank, column in enumerate(columns, start=1)\n            )\n        if end == len(eligibility.uids) or end % 1_024 == 0:\n            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n    query_norm = torch.linalg.vector_norm(queries, dim=1).numpy()\n    item_norm = torch.linalg.vector_norm(items, dim=1).numpy()\n    diagnostics = {\n        \"query_norm_mean\": float(query_norm.mean()),\n        \"query_norm_std\": float(query_norm.std()),\n        \"item_norm_mean\": float(item_norm.mean()),\n        \"item_norm_std\": float(item_norm.std()),\n    }\n    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n\n\ndef write_ranking(frame: pd.DataFrame, output: Path) -> None:\n    output.parent.mkdir(parents=True, exist_ok=True)\n    if output.suffix == \".parquet\":\n        frame.to_parquet(output, index=False, compression=\"zstd\")\n    elif output.suffix == \".csv\":\n        frame.to_csv(output, index=False)\n    else:\n        raise ValueError(\"--output must end in .parquet or .csv\")\n\n\ndef main() -> int:\n    parser = argparse.ArgumentParser(description=__doc__)\n    parser.add_argument(\n        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n    )\n    parser.add_argument(\"--output\", type=Path, required=True)\n    parser.add_argument(\"--public-dir\", type=Path, required=True)\n    parser.add_argument(\"--prepared-cache\", type=Path)\n    parser.add_argument(\"--device\", choices=(\"cpu\", \"mps\"), default=\"cpu\")\n    parser.add_argument(\"--threads\", type=int, default=8)\n    parser.add_argument(\"--bptt-steps\", type=int, default=Config.bptt_steps)\n    parser.add_argument(\n        \"--user-batch-size\", type=int, default=Config.user_batch_size\n    )\n    parser.add_argument(\"--epochs\", type=int, default=Config.epochs)\n    parser.add_argument(\"--learning-rate\", type=float, default=Config.learning_rate)\n    parser.add_argument(\n        \"--loss-microbatch-size\",\n        type=int,\n        default=Config.loss_microbatch_size,\n    )\n    parser.add_argument(\n        \"--negative-filter-scope\",\n        choices=(\"full-training-history\", \"last-100\"),\n        default=Config.negative_filter_scope,\n    )\n    parser.add_argument(\n        \"--target-weighting\",\n        choices=(\"discovery-graded\", \"organic-strong\", \"uniform\"),\n        default=Config.target_weighting,\n    )\n    parser.add_argument(\n        \"--ordinary-target-weight\",\n        type=float,\n        default=Config.ordinary_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-strong-target-weight\",\n        type=float,\n        default=Config.organic_strong_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-like-target-weight\",\n        type=float,\n        default=Config.organic_like_target_weight,\n    )\n    parser.add_argument(\n        \"--discovery-horizon-days\",\n        type=int,\n        default=Config.discovery_horizon_days,\n    )\n    parser.add_argument(\n        \"--validation-fraction\",\n        type=float,\n        default=Config.validation_fraction,\n    )\n    parser.add_argument(\n        \"--max-train-targets-per-user\",\n        type=int,\n        default=Config.max_train_targets_per_user,\n        help=\"retain this many recent pre-validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--max-validation-targets-per-user\",\n        type=int,\n        default=Config.max_validation_targets_per_user,\n        help=\"retain this many final validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--early-stopping-patience\",\n        type=int,\n        default=Config.early_stopping_patience,\n    )\n    parser.add_argument(\n        \"--early-stopping-min-delta\",\n        type=float,\n        default=Config.early_stopping_min_delta,\n    )\n    parser.add_argument(\"--checkpoint-dir\", type=Path)\n    parser.add_argument(\"--resume-checkpoint\", type=Path)\n    parser.add_argument(\"--seed\", type=int, default=Config.seed)\n    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n    parser.add_argument(\"--prepare-only\", action=\"store_true\")\n    args = parser.parse_args()\n\n    if args.threads < 1 or args.bptt_steps < 2 or args.user_batch_size < 1:\n        parser.error(\"threads, BPTT steps, and user batch size must be positive\")\n    if (\n        args.epochs < 1\n        or args.learning_rate <= 0\n        or args.loss_microbatch_size < 1\n        or args.early_stopping_patience < 1\n        or args.early_stopping_min_delta < 0\n        or args.ordinary_target_weight <= 0\n        or args.organic_strong_target_weight <= 0\n        or args.organic_like_target_weight <= 0\n        or args.discovery_horizon_days < 1\n        or args.max_train_targets_per_user < 0\n        or args.max_validation_targets_per_user < 0\n    ):\n        parser.error(\"training counts, learning rate, and patience are invalid\")\n    if not 0.0 < args.validation_fraction < 1.0:\n        parser.error(\"validation fraction must be strictly between zero and one\")\n    public = args.public_dir.resolve()\n    if not (public / \"data\" / \"candidate_catalog.parquet\").is_file():\n        parser.error(f\"public task data not found under {public}\")\n    config = Config(\n        bptt_steps=args.bptt_steps,\n        user_batch_size=args.user_batch_size,\n        epochs=args.epochs,\n        learning_rate=args.learning_rate,\n        loss_microbatch_size=args.loss_microbatch_size,\n        negative_filter_scope=args.negative_filter_scope,\n        target_weighting=args.target_weighting,\n        ordinary_target_weight=args.ordinary_target_weight,\n        organic_strong_target_weight=args.organic_strong_target_weight,\n        organic_like_target_weight=args.organic_like_target_weight,\n        discovery_horizon_days=args.discovery_horizon_days,\n        validation_fraction=args.validation_fraction,\n        max_train_targets_per_user=args.max_train_targets_per_user,\n        max_validation_targets_per_user=args.max_validation_targets_per_user,\n        early_stopping_patience=args.early_stopping_patience,\n        early_stopping_min_delta=args.early_stopping_min_delta,\n        seed=args.seed,\n    )\n    torch.set_num_threads(args.threads)\n    torch.set_num_interop_threads(1)\n    seed_everything(config.seed)\n    device = torch.device(args.device)\n    if device.type == \"mps\" and not torch.backends.mps.is_available():\n        parser.error(\"MPS was requested but is unavailable\")\n\n    started = time.monotonic()\n    prepared, eligibility = load_or_prepare(\n        public,\n        args.stage,\n        config,\n        args.prepared_cache.resolve() if args.prepared_cache else None,\n    )\n    target_partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    if args.prepare_only:\n        print(\n            json.dumps(\n                {\n                    \"stage\": args.stage,\n                    \"sequence_users\": len(prepared.user_ids),\n                    \"sequence_tokens\": len(prepared.sequence_items),\n                    \"next_item_targets\": prepared.target_count,\n                    \"selected_training_targets\": int(\n                        target_partition.training_counts.sum()\n                    ),\n                    \"selected_validation_targets\": int(\n                        target_partition.validation_counts.sum()\n                    ),\n                    \"discarded_old_targets\": int(\n                        target_partition.window_starts.sum()\n                    ),\n                    \"target_users\": len(eligibility.uids),\n                    \"runtime_seconds\": round(time.monotonic() - started, 3),\n                    \"config\": asdict(config),\n                },\n                indent=2,\n            )\n        )\n        return 0\n\n    model, training_history = train_model(\n        public,\n        args.stage,\n        prepared,\n        config,\n        device,\n        args.checkpoint_dir.resolve() if args.checkpoint_dir else None,\n        args.resume_checkpoint.resolve() if args.resume_checkpoint else None,\n    )\n    ranking, embedding_diagnostics = rank_candidates(\n        model,\n        prepared,\n        eligibility,\n        config,\n        device,\n        args.ranking_batch_size,\n    )\n    write_ranking(ranking, args.output.resolve())\n    print(\n        json.dumps(\n            {\n                \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n                \"stage\": args.stage,\n                \"output\": str(args.output.resolve()),\n                \"rows\": len(ranking),\n                \"users\": int(ranking.uid.nunique()),\n                \"runtime_seconds\": round(time.monotonic() - started, 3),\n                \"public_inputs_only\": True,\n                \"architecture\": {\n                    \"family\": \"pure-windowed-sequence-two-tower\",\n                    \"sequence_training\": (\n                        \"every-adjacent-target-within-recent-chronological-window\"\n                    ),\n                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n                    \"bptt_hidden_state\": \"carried-and-detached\",\n                    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n                    \"user_id_embedding\": False,\n                    \"user_mlp\": \"582-512-256-192\",\n                    \"item_mlp\": \"196-512-256-192\",\n                    \"normalization\": \"none\",\n                    \"score\": \"raw-dot-product\",\n                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n                    \"negative_sampling\": (\n                        \"24-uniform-plus-8-propensity-corrected-inbatch\"\n                    ),\n                    \"false_negative_filter\": config.negative_filter_scope,\n                    \"target_weighting\": config.target_weighting,\n                },\n                \"config\": asdict(config),\n                \"sequence_tokens\": len(prepared.sequence_items),\n                \"all_next_item_targets\": prepared.target_count,\n                \"selected_training_targets\": int(\n                    target_partition.training_counts.sum()\n                ),\n                \"selected_validation_targets\": int(\n                    target_partition.validation_counts.sum()\n                ),\n                \"discarded_old_targets\": int(target_partition.window_starts.sum()),\n                \"training_history\": training_history,\n                \"embedding_diagnostics\": embedding_diagnostics,\n                \"torch_version\": torch.__version__,\n                \"device\": str(device),\n            },\n            indent=2,\n        )\n    )\n    return 0\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:40:05.663Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-919f056d-0825-4432-9977-f1c2bcb4597b",
              "process_id": "51779",
              "command": [
                "/bin/sh",
                "-lc",
                "sed -n '760,1185p' /app/solution/train_current_model.py && sed -n '1185,1785p' /app/solution/train_current_model.py && sed -n '1860,2160p' /app/solution/train_current_model.py"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "read",
                  "cmd": "sed -n '760,1185p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                },
                {
                  "type": "read",
                  "cmd": "sed -n '1185,1785p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                },
                {
                  "type": "read",
                  "cmd": "sed -n '1860,2160p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "    )\n\n\ndef event_sequence(\n    model: base.SequentialTwoTower,\n    items: torch.Tensor,\n    features: torch.Tensor,\n    hidden: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    inputs = torch.cat([model.context_embedding(items), features], dim=-1)\n    projected = model.event_projection(inputs)\n    return model.sequence_encoder(projected, hidden)\n\n\ndef pool_explicit_states(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    state_ids: np.ndarray,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:\n    unique_states, inverse = np.unique(state_ids, return_inverse=True)\n    liked_items = torch.from_numpy(\n        prepared.liked_states[unique_states].astype(np.int64)\n    ).to(device)\n    disliked_items = torch.from_numpy(\n        prepared.disliked_states[unique_states].astype(np.int64)\n    ).to(device)\n    liked_vectors = model._mean_context_channel(liked_items)\n    disliked_vectors = model._mean_context_channel(disliked_items)\n    inverse_rows = torch.from_numpy(inverse.astype(np.int64)).to(device)\n    counts = prepared.state_counts[state_ids]\n    return (\n        liked_vectors[inverse_rows],\n        disliked_vectors[inverse_rows],\n        torch.from_numpy(counts.astype(np.float32)).to(device),\n    )\n\n\ndef user_queries(\n    model: base.SequentialTwoTower,\n    sequence_vectors: torch.Tensor,\n    liked_vectors: torch.Tensor,\n    disliked_vectors: torch.Tensor,\n    user_features: torch.Tensor,\n) -> torch.Tensor:\n    return model.user_tower(\n        torch.cat(\n            [sequence_vectors, liked_vectors, disliked_vectors, user_features],\n            dim=1,\n        )\n    )\n\n\ndef candidate_vectors(\n    model: base.SequentialTwoTower,\n    positives: torch.Tensor,\n    negatives: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    all_items = torch.cat([positives, negatives.reshape(-1)])\n    unique_items, inverse = torch.unique(all_items, return_inverse=True)\n    encoded = model.encode_items(unique_items)\n    positive_vectors = encoded[inverse[: len(positives)]]\n    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n        len(positives), negatives.shape[1], -1\n    )\n    return positive_vectors, negative_vectors\n\n\ndef history_windows(\n    sequence: np.ndarray,\n    start: int,\n    count: int,\n    width: int,\n    padding_item: int,\n) -> np.ndarray:\n    base_start = max(0, start - width + 1)\n    segment = sequence[base_start : start + count]\n    padded = np.concatenate(\n        [np.full(width - 1, padding_item, dtype=np.uint16), segment]\n    )\n    windows = np.lib.stride_tricks.sliding_window_view(padded, width)\n    offset = start - base_start\n    return windows[offset : offset + count].copy()\n\n\ndef corrected_negative_loss(\n    logits: torch.Tensor,\n    correction: torch.Tensor,\n    config: Config,\n) -> torch.Tensor:\n    raw = F.softplus(logits)\n    total = config.uniform_negatives + config.inbatch_negatives\n    result = torch.zeros(len(logits), device=logits.device)\n    if config.uniform_negatives:\n        result += config.uniform_negatives * raw[\n            :, : config.uniform_negatives\n        ].mean(dim=1)\n    if config.inbatch_negatives:\n        selected = slice(config.uniform_negatives, total)\n        weights = correction[:, selected]\n        result += config.inbatch_negatives * (\n            (raw[:, selected] * weights).sum(dim=1)\n            / weights.sum(dim=1).clamp_min(1.0e-6)\n        )\n    return result / total\n\n\ndef retained_target_window_starts(\n    total_targets: np.ndarray,\n    validation_counts: np.ndarray,\n    training_counts: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return the discarded prefix before the retained chronological suffix.\"\"\"\n    training_region_ends = total_targets - validation_counts\n    window_starts = training_region_ends - training_counts\n    if (\n        np.any(window_starts < 0)\n        or np.any(training_counts < 0)\n        or np.any(validation_counts < 0)\n    ):\n        raise RuntimeError(\"chronological target partition produced negative counts\")\n    if not np.array_equal(\n        window_starts + training_counts + validation_counts, total_targets\n    ):\n        raise RuntimeError(\"chronological target window is not a final contiguous suffix\")\n    return window_starts\n\n\ndef chronological_target_partition(\n    prepared: SequenceData,\n    validation_fraction: float,\n    max_train_targets_per_user: int,\n    max_validation_targets_per_user: int,\n) -> TargetPartition:\n    \"\"\"Select a recent contiguous window with a final out-of-time BCE suffix.\"\"\"\n    totals = np.maximum(prepared.lengths - 1, 0).astype(np.int64)\n    validation = np.floor(totals * validation_fraction).astype(np.int64)\n    validation[(totals >= 2) & (validation == 0)] = 1\n    if max_validation_targets_per_user:\n        validation = np.minimum(validation, max_validation_targets_per_user)\n\n    history_training = totals - validation\n    training = history_training.copy()\n    if max_train_targets_per_user:\n        training = np.minimum(training, max_train_targets_per_user)\n    window_starts = retained_target_window_starts(totals, validation, training)\n    return TargetPartition(\n        window_starts=window_starts,\n        training_counts=training,\n        validation_counts=validation,\n        history_training_counts=history_training,\n    )\n\n\ndef load_organic_like_outcomes(\n    public: Path, stage: str, item_ids: np.ndarray\n) -> dict[int, dict[int, np.ndarray]]:\n    \"\"\"Load mapped organic-like timestamps from public fitting history.\"\"\"\n    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n    frames = [\n        pd.read_parquet(\n            public / \"data\" / f\"{prefix}_likes.parquet\",\n            columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n        )\n        for prefix in prefixes\n    ]\n    likes = pd.concat(frames, ignore_index=True)\n    likes = likes[likes.is_organic == 1].copy()\n    mapped = pd.Index(item_ids).get_indexer(\n        likes.item_id.to_numpy(dtype=np.int64)\n    )\n    likes = likes.loc[mapped >= 0, [\"uid\", \"timestamp\"]].copy()\n    likes[\"item\"] = mapped[mapped >= 0].astype(np.int32, copy=False)\n    likes = likes.sort_values([\"uid\", \"item\", \"timestamp\"], kind=\"stable\")\n    nested: dict[int, dict[int, list[int]]] = {}\n    for raw_uid, raw_timestamp, raw_item in likes.itertuples(\n        index=False, name=None\n    ):\n        nested.setdefault(int(raw_uid), {}).setdefault(int(raw_item), []).append(\n            int(raw_timestamp)\n        )\n    result = {\n        uid: {\n            item: np.asarray(timestamps, dtype=np.int64)\n            for item, timestamps in items.items()\n        }\n        for uid, items in nested.items()\n    }\n    log(\n        f\"loaded organic-like outcomes: rows={len(likes):,} \"\n        f\"users={len(result):,}\"\n    )\n    return result\n\n\ndef build_target_weights(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    training_counts: np.ndarray,\n    config: Config,\n) -> np.ndarray:\n    \"\"\"Build nonzero per-token weights without dropping adjacent targets.\"\"\"\n    if config.target_weighting == \"uniform\":\n        weights = np.ones(len(prepared.sequence_items), dtype=np.float32)\n    else:\n        weights = np.full(\n            len(prepared.sequence_items),\n            config.ordinary_target_weight,\n            dtype=np.float32,\n        )\n        organic_strong = (\n            (prepared.event_features[:, 0] > 0.5)\n            & (prepared.event_features[:, 1] >= 0.8)\n        )\n        weights[organic_strong] = config.organic_strong_target_weight\n        if config.target_weighting == \"discovery-graded\":\n            like_outcomes = load_organic_like_outcomes(\n                public, stage, prepared.item_ids\n            )\n            history_end = (\n                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n            )\n            horizon = config.discovery_horizon_days * base.DAY\n            grade_three = 0\n            for user_row, uid in enumerate(prepared.user_ids):\n                start = int(prepared.offsets[user_row])\n                end = int(prepared.offsets[user_row + 1])\n                if end - start < 2:\n                    continue\n                last_training_target = start + int(training_counts[user_row])\n                first_validation_target = last_training_target + 1\n                split_timestamp = (\n                    int(prepared.sequence_timestamps[first_validation_target])\n                    if first_validation_target < end\n                    else history_end\n                )\n                user_likes = like_outcomes.get(int(uid), {})\n                seen = {int(prepared.sequence_items[start])}\n                for position in range(start + 1, end):\n                    item = int(prepared.sequence_items[position])\n                    novel = item not in seen\n                    seen.add(item)\n                    if not novel:\n                        # Repeats remain training examples, but they cannot be\n                        # eligible discovery outcomes at the corresponding\n                        # cutoff and therefore keep only the ordinary weight.\n                        weights[position] = config.ordinary_target_weight\n                        continue\n                    timestamps = user_likes.get(item)\n                    if timestamps is None:\n                        continue\n                    timestamp = int(prepared.sequence_timestamps[position])\n                    upper = min(\n                        timestamp + horizon,\n                        split_timestamp\n                        if position <= last_training_target\n                        else history_end,\n                    )\n                    outcome = int(np.searchsorted(timestamps, timestamp, side=\"left\"))\n                    if outcome < len(timestamps) and int(timestamps[outcome]) < upper:\n                        weights[position] = config.organic_like_target_weight\n                        grade_three += 1\n            log(\n                f\"grade-3 first-encounter targets={grade_three:,} \"\n                f\"horizon_days={config.discovery_horizon_days}\"\n            )\n    log(\n        f\"target weighting={config.target_weighting} \"\n        f\"min={weights.min():.3f} mean={weights.mean():.3f} \"\n        f\"max={weights.max():.3f}\"\n    )\n    return weights\n\n\ndef build_dense_block(\n    prepared: SequenceData,\n    target_weights: np.ndarray,\n    users: np.ndarray,\n    window_starts: np.ndarray,\n    process_counts: np.ndarray,\n    score_starts: np.ndarray,\n    start: int,\n    steps: int,\n    config: Config,\n) -> tuple[np.ndarray, ...]:\n    \"\"\"Build one causal sequence block and mark the target rows to score.\"\"\"\n    batch_size = len(users)\n    padding_item = len(prepared.item_ids)\n    input_items = np.full((batch_size, steps), padding_item, dtype=np.uint16)\n    event_features = np.zeros((batch_size, steps, 3), dtype=np.float16)\n    activity_features = np.zeros((batch_size, steps, 4), dtype=np.float16)\n    state_ids = np.zeros((batch_size, steps), dtype=np.uint32)\n    targets = np.zeros((batch_size, steps), dtype=np.uint16)\n    weights = np.ones((batch_size, steps), dtype=np.float32)\n    scored = np.zeros((batch_size, steps), dtype=bool)\n    histories = np.full(\n        (batch_size, steps, config.bptt_steps),\n        padding_item,\n        dtype=np.uint16,\n    )\n    processed = np.zeros(batch_size, dtype=np.int32)\n\n    lengths = prepared.lengths\n    for row, user_row in enumerate(users):\n        count = min(steps, max(int(process_counts[row]) - start, 0))\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        window_start = int(window_starts[row])\n        absolute_start = window_start + start\n        positions = slice(\n            offset + absolute_start,\n            offset + absolute_start + count,\n        )\n        target_positions = slice(\n            offset + absolute_start + 1,\n            offset + absolute_start + count + 1,\n        )\n        input_items[row, :count] = prepared.sequence_items[positions]\n        event_features[row, :count] = prepared.event_features[positions]\n        activity_features[row, :count] = prepared.activity_features[positions]\n        state_ids[row, :count] = prepared.state_ids[positions]\n        targets[row, :count] = prepared.sequence_items[target_positions]\n        weights[row, :count] = target_weights[target_positions]\n        score_from = min(count, max(int(score_starts[row]) - start, 0))\n        scored[row, score_from:count] = True\n        processed[row] = count\n        user_sequence = prepared.sequence_items[\n            offset : offset + int(lengths[user_row])\n        ]\n        histories[row, :count] = history_windows(\n            user_sequence,\n            absolute_start,\n            count,\n            config.bptt_steps,\n            padding_item,\n        )\n    return (\n        input_items,\n        event_features,\n        activity_features,\n        state_ids,\n        targets,\n        scored,\n        histories,\n        processed,\n        weights,\n    )\n\n\ndef score_target_microbatches(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    sequence_vectors: torch.Tensor,\n    flat_states: np.ndarray,\n    flat_activity: np.ndarray,\n    positive_items: torch.Tensor,\n    negatives: torch.Tensor,\n    negative_weights: torch.Tensor,\n    sample_weights: np.ndarray,\n    device: torch.device,\n    backward: bool,\n) -> tuple[dict[str, float], torch.Tensor | None]:\n    \"\"\"Compute one logical block's exact BCE in bounded-memory slices.\"\"\"\n    target_count = len(positive_items)\n    total_weight = float(sample_weights.sum())\n    if total_weight <= 0:\n        raise RuntimeError(\"target block has no positive sample weight\")\n    sequence_gradient = torch.zeros_like(sequence_vectors) if backward else None\n    statistics = {\n        \"loss_sum\": 0.0,\n        \"positive_sum\": 0.0,\n        \"negative_sum\": 0.0,\n        \"pair_correct\": 0.0,\n        \"weight_sum\": 0.0,\n    }\n    for begin in range(0, target_count, config.loss_microbatch_size):\n        end = min(begin + config.loss_microbatch_size, target_count)\n        selected_states = flat_states[begin:end]\n        if backward:\n            sequence_input = (\n                sequence_vectors[begin:end].detach().requires_grad_(True)\n            )\n        else:\n            sequence_input = sequence_vectors[begin:end]\n        liked_vectors, disliked_vectors, _ = pool_explicit_states(\n            model, prepared, selected_states, device\n        )\n        counts = prepared.state_counts[selected_states]\n        numeric = np.zeros((end - begin, 6), dtype=np.float32)\n        numeric[:, :4] = flat_activity[begin:end]\n        numeric[:, 4] = np.log1p(counts[:, 0]) / 6.0\n        numeric[:, 5] = np.log1p(counts[:, 1]) / 4.0\n        query_vectors = user_queries(\n            model,\n            sequence_input,\n            liked_vectors,\n            disliked_vectors,\n            torch.from_numpy(numeric).to(device),\n        )\n        positive_vectors, negative_vectors = candidate_vectors(\n            model,\n            positive_items[begin:end],\n            negatives[begin:end],\n        )\n        positive_logits = (query_vectors * positive_vectors).sum(dim=1)\n        negative_logits = torch.einsum(\n            \"bd,bkd->bk\", query_vectors, negative_vectors\n        )\n        positive_loss = F.softplus(-positive_logits)\n        negative_loss = corrected_negative_loss(\n            negative_logits, negative_weights[begin:end], config\n        )\n        selected_weights = torch.from_numpy(\n            sample_weights[begin:end].astype(np.float32, copy=False)\n        ).to(device)\n        loss_sum = (\n            selected_weights * (positive_loss + negative_loss) / 2.0\n        ).sum()\n        if not bool(torch.isfinite(loss_sum)):\n            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n        if backward:\n            (loss_sum / total_weight).backward()\n            if sequence_input.grad is None:\n            if sequence_input.grad is None:\n                raise RuntimeError(\"sequence microbatch did not produce a gradient\")\n            sequence_gradient[begin:end] = sequence_input.grad\n        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n        statistics[\"positive_sum\"] += float(positive_logits.detach().sum().cpu())\n        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n        statistics[\"pair_correct\"] += float(\n            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n        )\n        statistics[\"weight_sum\"] += float(selected_weights.sum().detach().cpu())\n    return statistics, sequence_gradient\n\n\ndef release_accelerator_cache(device: torch.device) -> None:\n    if device.type == \"mps\":\n        torch.mps.empty_cache()\n\n\ndef run_training_epoch(\n    model: base.SequentialTwoTower,\n    optimizer: torch.optim.Optimizer,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    target_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    generator: torch.Generator,\n    device: torch.device,\n    epoch: int,\n) -> dict[str, float]:\n    model.train()\n    train_users = np.flatnonzero(target_counts > 0)\n    sorted_users = train_users[\n        np.argsort(target_counts[train_users], kind=\"stable\")\n    ]\n    groups = [\n        sorted_users[start : start + config.user_batch_size]\n        for start in range(0, len(sorted_users), config.user_batch_size)\n    ]\n    group_order = torch.randperm(len(groups), generator=generator).numpy()\n    negative_count = config.uniform_negatives + config.inbatch_negatives\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    total_positive = 0.0\n    total_negative = 0.0\n    total_pair_correct = 0.0\n    batches = 0\n    started = time.monotonic()\n\n    for group_number in group_order:\n        users = groups[int(group_number)]\n        group_counts = target_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_counts.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_counts,\n                np.zeros(len(users), dtype=np.int64),\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            optimizer.zero_grad(set_to_none=True)\n            statistics, sequence_gradient = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=True,\n            )\n            if sequence_gradient is None:\n                raise RuntimeError(\"training block omitted its sequence gradient\")\n            sequence_vectors.backward(sequence_gradient)\n            nn.utils.clip_grad_norm_(model.parameters(), config.gradient_clip)\n            optimizer.step()\n\n            count = len(positive_items)\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += count\n            total_weight += statistics[\"weight_sum\"]\n            total_positive += statistics[\"positive_sum\"]\n            total_negative += statistics[\"negative_sum\"]\n            total_pair_correct += statistics[\"pair_correct\"]\n            batches += 1\n            if batches % 25 == 0:\n                release_accelerator_cache(device)\n            if batches % 250 == 0:\n                batch_bce = statistics[\"loss_sum\"] / max(\n                    statistics[\"weight_sum\"], 1.0e-12\n                )\n                running_bce = total_loss / max(total_weight, 1.0e-12)\n                log(\n                    f\"epoch={epoch}/{config.epochs} batches={batches:,} \"\n                    f\"targets={total_targets:,} \"\n                    f\"batch_bce={batch_bce:.6f} \"\n                    f\"running_bce={running_bce:.6f} \"\n                    f\"elapsed={time.monotonic() - started:.1f}s\"\n                )\n\n    return {\n        \"epoch\": float(epoch),\n        \"loss\": total_loss / max(total_weight, 1.0e-12),\n        \"positive_logit\": total_positive / max(total_targets, 1),\n        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n        \"pair_accuracy\": total_pair_correct\n        / max(total_targets * negative_count, 1),\n        \"targets\": float(total_targets),\n        \"target_weight_sum\": total_weight,\n        \"batches\": float(batches),\n        \"seconds\": time.monotonic() - started,\n    }\n\n\n@torch.no_grad()\ndef evaluate_validation_bce(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    training_counts: np.ndarray,\n    validation_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    device: torch.device,\n) -> dict[str, float]:\n    \"\"\"Measure deterministic BCE on each user's chronological target suffix.\"\"\"\n    model.eval()\n    totals = training_counts + validation_counts\n    users_with_validation = np.flatnonzero(validation_counts > 0)\n    ordered = users_with_validation[\n        np.argsort(totals[users_with_validation], kind=\"stable\")\n    ]\n    groups = [\n        ordered[start : start + config.user_batch_size]\n        for start in range(0, len(ordered), config.user_batch_size)\n    ]\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 20_000)\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    started = time.monotonic()\n\n    for group_number, users in enumerate(groups, start=1):\n        group_totals = totals[users]\n        group_starts = training_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_totals.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_totals,\n                group_starts,\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0)\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            statistics, _ = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=False,\n            )\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += len(positive_items)\n            total_weight += statistics[\"weight_sum\"]\n        if group_number % 25 == 0:\n            release_accelerator_cache(device)\n    return {\n        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n        \"validation_targets\": float(total_targets),\n        \"validation_target_weight_sum\": total_weight,\n        \"validation_seconds\": time.monotonic() - started,\n    }\n\n\ndef snapshot_model(model: nn.Module) -> dict[str, torch.Tensor]:\n    return {\n        name: value.detach().cpu().clone()\n        for name, value in model.state_dict().items()\n    }\n\n\ndef save_epoch_checkpoint(\n    checkpoint_dir: Path,\n    epoch: int,\n    model_state: dict[str, torch.Tensor],\n    config: Config,\n    diagnostics: dict[str, float],\n    optimizer: torch.optim.Optimizer,\n    generator: torch.Generator,\n) -> Path:\n    checkpoint_dir.mkdir(parents=True, exist_ok=True)\n    path = checkpoint_dir / f\"epoch-{epoch:02d}.pt\"\n    torch.save(\n        {\n            \"epoch\": epoch,\n            \"config\": asdict(config),\n            \"diagnostics\": diagnostics,\n            \"model_state\": model_state,\n            \"optimizer_state\": optimizer.state_dict(),\n            \"generator_state\": generator.get_state(),\n        },\n        path,\n    )\n    log(f\"saved epoch checkpoint: {path}\")\n    return path\n\n\ndef train_model(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    config: Config,\n    device: torch.device,\n    checkpoint_dir: Path | None,\n    resume_checkpoint: Path | None,\n) -> tuple[base.SequentialTwoTower, list[dict[str, float]]]:\n    partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    training_counts = partition.training_counts\n    validation_counts = partition.validation_counts\n    log(\n        f\"chronological BCE window: train={int(training_counts.sum()):,} \"\n        f\"validation={int(validation_counts.sum()):,} \"\n        f\"selected={partition.selected_count:,} \"\n        f\"discarded_old_targets={int(partition.window_starts.sum()):,} \"\n        f\"all={prepared.target_count:,}\"\n    )\n    model = base.SequentialTwoTower(prepared.item_features, model_config(config)).to(\n        device\n    )\n    optimizer = torch.optim.AdamW(\n        model.parameters(), lr=config.learning_rate, weight_decay=config.weight_decay\n    )\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 10_000)\n    item_correction = build_item_correction(\n        prepared,\n        config,\n        partition.window_starts,\n        training_counts,\n    )\n    target_weights = build_target_weights(\n        public,\n        stage,\n        prepared,\n        partition.history_training_counts,\n        config,\n    )\n    known_positive_packed = (\n        build_known_positive_filter(prepared, partition.history_training_counts)\n        if config.negative_filter_scope == \"full-training-history\"\n        else None\n    )\n    history: list[dict[str, float]] = []\n    best_loss = float(\"inf\")\n    best_epoch = 0\n    best_state: dict[str, torch.Tensor] | None = None\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n            stored_config.get(\"max_validation_targets_per_user\", 0),\n        )\n        current_window_values = (\n            config.validation_fraction,\n            config.max_train_targets_per_user,\n            config.max_validation_targets_per_user,\n        )\n        objective_changed = (\n            stored_filter_scope != config.negative_filter_scope\n            or stored_target_weighting != config.target_weighting\n            or stored_weight_values != current_weight_values\n            or stored_window_values != current_window_values\n        )\n        model.load_state_dict(payload[\"model_state\"])\n        if \"optimizer_state\" in payload and not objective_changed:\n            optimizer.load_state_dict(payload[\"optimizer_state\"])\n            for group in optimizer.param_groups:\n                group[\"lr\"] = config.learning_rate\n                group[\"weight_decay\"] = config.weight_decay\n            log(f\"restored optimizer state from {resume_checkpoint}\")\n        else:\n            log(\n                f\"using a fresh AdamW optimizer after loading {resume_checkpoint}\"\n            )\n        if \"generator_state\" in payload and not objective_changed:\n            generator.set_state(payload[\"generator_state\"])\n        start_epoch = int(payload[\"epoch\"])\n        if start_epoch >= config.epochs:\n            raise RuntimeError(\n                f\"resume epoch {start_epoch} must be below --epochs {config.epochs}\"\n            )\n        prior = {\n            str(name): float(value)\n            for name, value in payload.get(\"diagnostics\", {}).items()\n        }\n        if objective_changed:\n            prior.pop(\"validation_loss\", None)\n            log(\n                \"BCE objective changed: filter \"\n                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n                \"target weighting \"\n                f\"{stored_target_weighting}->{config.target_weighting}, \"\n                f\"target window {stored_window_values}->{current_window_values}; \"\n                \"recomputing the resume checkpoint's validation BCE\"\n            )\n        if \"validation_loss\" not in prior:\n            prior.update(\n                evaluate_validation_bce(\n                    model,\n                    prepared,\n                    config,\n                    target_weights,\n                    partition.window_starts,\n                    training_counts,\n                    validation_counts,\n                    item_correction,\n                    known_positive_packed,\n                    device,\n                )\n            )\n        history.append(prior)\n        best_loss = float(prior[\"validation_loss\"])\n        best_epoch = start_epoch\n        best_state = snapshot_model(model)\n        log(\n            f\"resumed validation-BCE training: epoch={start_epoch} \"\n            f\"loss={best_loss:.6f}\"\n        )\n\n    for epoch in range(start_epoch + 1, config.epochs + 1):\n        diagnostics = run_training_epoch(\n            model,\n            optimizer,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            item_correction,\n            known_positive_packed,\n            generator,\n            device,\n            epoch,\n        )\n        validation = evaluate_validation_bce(\n            model,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            validation_counts,\n            item_correction,\n            known_positive_packed,\n            device,\n        )\n        diagnostics.update(validation)\n        history.append(diagnostics)\n        current_state = snapshot_model(model)\n        if checkpoint_dir is not None:\n            save_epoch_checkpoint(\n                checkpoint_dir,\n                epoch,\n                current_state,\n                config,\n                diagnostics,\n                optimizer,\n                generator,\n            )\n        improved = (\n            diagnostics[\"validation_loss\"]\n            < best_loss - config.early_stopping_min_delta\n        )\n        if improved:\n            best_loss = diagnostics[\"validation_loss\"]\n            best_epoch = epoch\n            best_state = current_state\n            epochs_without_improvement = 0\n            if checkpoint_dir is not None:\n                torch.save(\n                    {\n                        \"epoch\": epoch,\n                        \"config\": asdict(config),\n                        \"diagnostics\": diagnostics,\n                        \"model_state\": current_state,\n                        \"optimizer_state\": optimizer.state_dict(),\n                        \"generator_state\": generator.get_state(),\n                    },\n                    checkpoint_dir / \"best.pt\",\n                )\n        else:\n            epochs_without_improvement += 1\n        log(\n            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n            f\"pair_accuracy={diagnostics['pair_accuracy']:.3f} \"\n            f\"train_targets={int(diagnostics['targets']):,} \"\n            f\"validation_targets={int(diagnostics['validation_targets']):,} \"\n            f\"train_seconds={diagnostics['seconds']:.1f} \"\n            f\"validation_seconds={diagnostics['validation_seconds']:.1f}\"\n        )\n        release_accelerator_cache(device)\n        if epochs_without_improvement >= config.early_stopping_patience:\n            log(\n                f\"early stopping after epoch={epoch}; \"\n                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n            )\n            break\n\n    if best_state is None:\n        raise RuntimeError(\"training did not produce a valid checkpoint\")\n    model.load_state_dict(best_state)\n    model.to(device).eval()\n    log(\n        f\"restored best validation-BCE checkpoint: epoch={best_epoch} \"\n        f\"loss={best_loss:.6f}\"\n    )\n    return model, history\n\n\n@torch.inference_mode()\ndef inference_queries(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n    device: torch.device,\n    ranking_batch_size: int,\n) -> tuple[pd.DataFrame, dict[str, float]]:\n    model.eval()\n    queries = inference_queries(model, prepared, config, device)\n    item_parts: list[torch.Tensor] = []\n    for start in range(0, len(prepared.item_ids), 2_048):\n        rows = torch.arange(\n            start,\n            min(start + 2_048, len(prepared.item_ids)),\n            dtype=torch.long,\n            device=device,\n        )\n        item_parts.append(model.encode_items(rows).cpu())\n    items = torch.cat(item_parts)\n    rows: list[tuple[int, int, int]] = []\n    for start in range(0, len(eligibility.uids), ranking_batch_size):\n        end = min(start + ranking_batch_size, len(eligibility.uids))\n        scores = queries[start:end] @ items.T\n        eligible = np.unpackbits(\n            eligibility.packed[start:end],\n            axis=1,\n            count=len(prepared.item_ids),\n            bitorder=\"little\",\n        ).astype(bool, copy=False)\n        scores.masked_fill_(~torch.from_numpy(eligible), -torch.inf)\n        selected = torch.topk(scores, k=base.TOP_N, dim=1).indices.numpy()\n        for local_row, columns in enumerate(selected):\n            uid = int(eligibility.uids[start + local_row])\n            rows.extend(\n                (uid, int(prepared.item_ids[column]), rank)\n                for rank, column in enumerate(columns, start=1)\n            )\n        if end == len(eligibility.uids) or end % 1_024 == 0:\n            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n    query_norm = torch.linalg.vector_norm(queries, dim=1).numpy()\n    item_norm = torch.linalg.vector_norm(items, dim=1).numpy()\n    diagnostics = {\n        \"query_norm_mean\": float(query_norm.mean()),\n        \"query_norm_std\": float(query_norm.std()),\n        \"item_norm_mean\": float(item_norm.mean()),\n        \"item_norm_std\": float(item_norm.std()),\n    }\n    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n\n\ndef write_ranking(frame: pd.DataFrame, output: Path) -> None:\n    output.parent.mkdir(parents=True, exist_ok=True)\n    if output.suffix == \".parquet\":\n        frame.to_parquet(output, index=False, compression=\"zstd\")\n    elif output.suffix == \".csv\":\n        frame.to_csv(output, index=False)\n    else:\n        raise ValueError(\"--output must end in .parquet or .csv\")\n\n\ndef main() -> int:\n    parser = argparse.ArgumentParser(description=__doc__)\n    parser.add_argument(\n        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n    )\n    parser.add_argument(\"--output\", type=Path, required=True)\n    parser.add_argument(\"--public-dir\", type=Path, required=True)\n    parser.add_argument(\"--prepared-cache\", type=Path)\n    parser.add_argument(\"--device\", choices=(\"cpu\", \"mps\"), default=\"cpu\")\n    parser.add_argument(\"--threads\", type=int, default=8)\n    parser.add_argument(\"--bptt-steps\", type=int, default=Config.bptt_steps)\n    parser.add_argument(\n        \"--user-batch-size\", type=int, default=Config.user_batch_size\n    )\n    parser.add_argument(\"--epochs\", type=int, default=Config.epochs)\n    parser.add_argument(\"--learning-rate\", type=float, default=Config.learning_rate)\n    parser.add_argument(\n        \"--loss-microbatch-size\",\n        type=int,\n        default=Config.loss_microbatch_size,\n    )\n    parser.add_argument(\n        \"--negative-filter-scope\",\n        choices=(\"full-training-history\", \"last-100\"),\n        default=Config.negative_filter_scope,\n    )\n    parser.add_argument(\n        \"--target-weighting\",\n        choices=(\"discovery-graded\", \"organic-strong\", \"uniform\"),\n        default=Config.target_weighting,\n    )\n    parser.add_argument(\n        \"--ordinary-target-weight\",\n        type=float,\n        default=Config.ordinary_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-strong-target-weight\",\n        type=float,\n        default=Config.organic_strong_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-like-target-weight\",\n        type=float,\n        default=Config.organic_like_target_weight,\n    )\n    parser.add_argument(\n        \"--discovery-horizon-days\",\n        type=int,\n        default=Config.discovery_horizon_days,\n    )\n    parser.add_argument(\n        \"--validation-fraction\",\n        type=float,\n        default=Config.validation_fraction,\n    )\n    parser.add_argument(\n        \"--max-train-targets-per-user\",\n        type=int,\n        default=Config.max_train_targets_per_user,\n        help=\"retain this many recent pre-validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--max-validation-targets-per-user\",\n        type=int,\n        default=Config.max_validation_targets_per_user,\n        help=\"retain this many final validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--early-stopping-patience\",\n        type=int,\n        default=Config.early_stopping_patience,\n    )\n    parser.add_argument(\n        \"--early-stopping-min-delta\",\n        type=float,\n        default=Config.early_stopping_min_delta,\n    )\n    parser.add_argument(\"--checkpoint-dir\", type=Path)\n    parser.add_argument(\"--resume-checkpoint\", type=Path)\n    parser.add_argument(\"--seed\", type=int, default=Config.seed)\n    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n    parser.add_argument(\"--prepare-only\", action=\"store_true\")\n    args = parser.parse_args()\n\n    if args.threads < 1 or args.bptt_steps < 2 or args.user_batch_size < 1:\n        parser.error(\"threads, BPTT steps, and user batch size must be positive\")\n    if (\n        args.epochs < 1\n        or args.learning_rate <= 0\n        or args.loss_microbatch_size < 1\n        or args.early_stopping_patience < 1\n        or args.early_stopping_min_delta < 0\n        or args.ordinary_target_weight <= 0\n        or args.organic_strong_target_weight <= 0\n        or args.organic_like_target_weight <= 0\n        or args.discovery_horizon_days < 1\n        or args.max_train_targets_per_user < 0\n        or args.max_validation_targets_per_user < 0\n    ):\n        parser.error(\"training counts, learning rate, and patience are invalid\")\n    if not 0.0 < args.validation_fraction < 1.0:\n        parser.error(\"validation fraction must be strictly between zero and one\")\n    public = args.public_dir.resolve()\n    if not (public / \"data\" / \"candidate_catalog.parquet\").is_file():\n        parser.error(f\"public task data not found under {public}\")\n    config = Config(\n        bptt_steps=args.bptt_steps,\n        user_batch_size=args.user_batch_size,\n        epochs=args.epochs,\n        learning_rate=args.learning_rate,\n        loss_microbatch_size=args.loss_microbatch_size,\n        negative_filter_scope=args.negative_filter_scope,\n        target_weighting=args.target_weighting,\n        ordinary_target_weight=args.ordinary_target_weight,\n        organic_strong_target_weight=args.organic_strong_target_weight,\n        organic_like_target_weight=args.organic_like_target_weight,\n        discovery_horizon_days=args.discovery_horizon_days,\n        validation_fraction=args.validation_fraction,\n        max_train_targets_per_user=args.max_train_targets_per_user,\n        max_validation_targets_per_user=args.max_validation_targets_per_user,\n        early_stopping_patience=args.early_stopping_patience,\n        early_stopping_min_delta=args.early_stopping_min_delta,\n        seed=args.seed,\n    )\n    torch.set_num_threads(args.threads)\n    torch.set_num_interop_threads(1)\n    seed_everything(config.seed)\n    device = torch.device(args.device)\n    if device.type == \"mps\" and not torch.backends.mps.is_available():\n        parser.error(\"MPS was requested but is unavailable\")\n\n    started = time.monotonic()\n    prepared, eligibility = load_or_prepare(\n        public,\n        args.stage,\n        config,\n        args.prepared_cache.resolve() if args.prepared_cache else None,\n    )\n    target_partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    if args.prepare_only:\n        print(\n            json.dumps(\n                {\n                    \"stage\": args.stage,\n                    \"sequence_users\": len(prepared.user_ids),\n                    \"sequence_tokens\": len(prepared.sequence_items),\n                    \"next_item_targets\": prepared.target_count,\n                    \"selected_training_targets\": int(\n                        target_partition.training_counts.sum()\n                    ),\n                    \"selected_validation_targets\": int(\n                        target_partition.validation_counts.sum()\n                    ),\n                    \"discarded_old_targets\": int(\n                        target_partition.window_starts.sum()\n                    ),\n                    \"target_users\": len(eligibility.uids),\n                    \"runtime_seconds\": round(time.monotonic() - started, 3),\n                    \"config\": asdict(config),\n                },\n                indent=2,\n            )\n        )\n        return 0\n\n    model, training_history = train_model(\n        public,\n        args.stage,\n        prepared,\n        config,\n        device,\n        args.checkpoint_dir.resolve() if args.checkpoint_dir else None,\n        args.resume_checkpoint.resolve() if args.resume_checkpoint else None,\n    )\n    ranking, embedding_diagnostics = rank_candidates(\n        model,\n        prepared,\n        eligibility,\n        config,\n        device,\n        args.ranking_batch_size,\n    )\n    write_ranking(ranking, args.output.resolve())\n    print(\n        json.dumps(\n            {\n                \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n                \"stage\": args.stage,\n                \"output\": str(args.output.resolve()),\n                \"rows\": len(ranking),\n                \"users\": int(ranking.uid.nunique()),\n                \"runtime_seconds\": round(time.monotonic() - started, 3),\n                \"public_inputs_only\": True,\n                \"architecture\": {\n                    \"family\": \"pure-windowed-sequence-two-tower\",\n                    \"sequence_training\": (\n                        \"every-adjacent-target-within-recent-chronological-window\"\n                    ),\n                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n                    \"bptt_hidden_state\": \"carried-and-detached\",\n                    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n                    \"user_id_embedding\": False,\n                    \"user_mlp\": \"582-512-256-192\",\n                    \"item_mlp\": \"196-512-256-192\",\n                    \"normalization\": \"none\",\n                    \"score\": \"raw-dot-product\",\n                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n                    \"negative_sampling\": (\n                        \"24-uniform-plus-8-propensity-corrected-inbatch\"\n                    ),\n                    \"false_negative_filter\": config.negative_filter_scope,\n                    \"target_weighting\": config.target_weighting,\n                },\n                \"config\": asdict(config),\n                \"sequence_tokens\": len(prepared.sequence_items),\n                \"all_next_item_targets\": prepared.target_count,\n                \"selected_training_targets\": int(\n                    target_partition.training_counts.sum()\n                ),\n                \"selected_validation_targets\": int(\n                    target_partition.validation_counts.sum()\n                ),\n                \"discarded_old_targets\": int(target_partition.window_starts.sum()),\n                \"training_history\": training_history,\n                \"embedding_diagnostics\": embedding_diagnostics,\n                \"torch_version\": torch.__version__,\n                \"device\": str(device),\n            },\n            indent=2,\n        )\n    )\n    return 0\n",
              "stderr": "",
              "aggregated_output": "    )\n\n\ndef event_sequence(\n    model: base.SequentialTwoTower,\n    items: torch.Tensor,\n    features: torch.Tensor,\n    hidden: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    inputs = torch.cat([model.context_embedding(items), features], dim=-1)\n    projected = model.event_projection(inputs)\n    return model.sequence_encoder(projected, hidden)\n\n\ndef pool_explicit_states(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    state_ids: np.ndarray,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:\n    unique_states, inverse = np.unique(state_ids, return_inverse=True)\n    liked_items = torch.from_numpy(\n        prepared.liked_states[unique_states].astype(np.int64)\n    ).to(device)\n    disliked_items = torch.from_numpy(\n        prepared.disliked_states[unique_states].astype(np.int64)\n    ).to(device)\n    liked_vectors = model._mean_context_channel(liked_items)\n    disliked_vectors = model._mean_context_channel(disliked_items)\n    inverse_rows = torch.from_numpy(inverse.astype(np.int64)).to(device)\n    counts = prepared.state_counts[state_ids]\n    return (\n        liked_vectors[inverse_rows],\n        disliked_vectors[inverse_rows],\n        torch.from_numpy(counts.astype(np.float32)).to(device),\n    )\n\n\ndef user_queries(\n    model: base.SequentialTwoTower,\n    sequence_vectors: torch.Tensor,\n    liked_vectors: torch.Tensor,\n    disliked_vectors: torch.Tensor,\n    user_features: torch.Tensor,\n) -> torch.Tensor:\n    return model.user_tower(\n        torch.cat(\n            [sequence_vectors, liked_vectors, disliked_vectors, user_features],\n            dim=1,\n        )\n    )\n\n\ndef candidate_vectors(\n    model: base.SequentialTwoTower,\n    positives: torch.Tensor,\n    negatives: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    all_items = torch.cat([positives, negatives.reshape(-1)])\n    unique_items, inverse = torch.unique(all_items, return_inverse=True)\n    encoded = model.encode_items(unique_items)\n    positive_vectors = encoded[inverse[: len(positives)]]\n    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n        len(positives), negatives.shape[1], -1\n    )\n    return positive_vectors, negative_vectors\n\n\ndef history_windows(\n    sequence: np.ndarray,\n    start: int,\n    count: int,\n    width: int,\n    padding_item: int,\n) -> np.ndarray:\n    base_start = max(0, start - width + 1)\n    segment = sequence[base_start : start + count]\n    padded = np.concatenate(\n        [np.full(width - 1, padding_item, dtype=np.uint16), segment]\n    )\n    windows = np.lib.stride_tricks.sliding_window_view(padded, width)\n    offset = start - base_start\n    return windows[offset : offset + count].copy()\n\n\ndef corrected_negative_loss(\n    logits: torch.Tensor,\n    correction: torch.Tensor,\n    config: Config,\n) -> torch.Tensor:\n    raw = F.softplus(logits)\n    total = config.uniform_negatives + config.inbatch_negatives\n    result = torch.zeros(len(logits), device=logits.device)\n    if config.uniform_negatives:\n        result += config.uniform_negatives * raw[\n            :, : config.uniform_negatives\n        ].mean(dim=1)\n    if config.inbatch_negatives:\n        selected = slice(config.uniform_negatives, total)\n        weights = correction[:, selected]\n        result += config.inbatch_negatives * (\n            (raw[:, selected] * weights).sum(dim=1)\n            / weights.sum(dim=1).clamp_min(1.0e-6)\n        )\n    return result / total\n\n\ndef retained_target_window_starts(\n    total_targets: np.ndarray,\n    validation_counts: np.ndarray,\n    training_counts: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return the discarded prefix before the retained chronological suffix.\"\"\"\n    training_region_ends = total_targets - validation_counts\n    window_starts = training_region_ends - training_counts\n    if (\n        np.any(window_starts < 0)\n        or np.any(training_counts < 0)\n        or np.any(validation_counts < 0)\n    ):\n        raise RuntimeError(\"chronological target partition produced negative counts\")\n    if not np.array_equal(\n        window_starts + training_counts + validation_counts, total_targets\n    ):\n        raise RuntimeError(\"chronological target window is not a final contiguous suffix\")\n    return window_starts\n\n\ndef chronological_target_partition(\n    prepared: SequenceData,\n    validation_fraction: float,\n    max_train_targets_per_user: int,\n    max_validation_targets_per_user: int,\n) -> TargetPartition:\n    \"\"\"Select a recent contiguous window with a final out-of-time BCE suffix.\"\"\"\n    totals = np.maximum(prepared.lengths - 1, 0).astype(np.int64)\n    validation = np.floor(totals * validation_fraction).astype(np.int64)\n    validation[(totals >= 2) & (validation == 0)] = 1\n    if max_validation_targets_per_user:\n        validation = np.minimum(validation, max_validation_targets_per_user)\n\n    history_training = totals - validation\n    training = history_training.copy()\n    if max_train_targets_per_user:\n        training = np.minimum(training, max_train_targets_per_user)\n    window_starts = retained_target_window_starts(totals, validation, training)\n    return TargetPartition(\n        window_starts=window_starts,\n        training_counts=training,\n        validation_counts=validation,\n        history_training_counts=history_training,\n    )\n\n\ndef load_organic_like_outcomes(\n    public: Path, stage: str, item_ids: np.ndarray\n) -> dict[int, dict[int, np.ndarray]]:\n    \"\"\"Load mapped organic-like timestamps from public fitting history.\"\"\"\n    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n    frames = [\n        pd.read_parquet(\n            public / \"data\" / f\"{prefix}_likes.parquet\",\n            columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n        )\n        for prefix in prefixes\n    ]\n    likes = pd.concat(frames, ignore_index=True)\n    likes = likes[likes.is_organic == 1].copy()\n    mapped = pd.Index(item_ids).get_indexer(\n        likes.item_id.to_numpy(dtype=np.int64)\n    )\n    likes = likes.loc[mapped >= 0, [\"uid\", \"timestamp\"]].copy()\n    likes[\"item\"] = mapped[mapped >= 0].astype(np.int32, copy=False)\n    likes = likes.sort_values([\"uid\", \"item\", \"timestamp\"], kind=\"stable\")\n    nested: dict[int, dict[int, list[int]]] = {}\n    for raw_uid, raw_timestamp, raw_item in likes.itertuples(\n        index=False, name=None\n    ):\n        nested.setdefault(int(raw_uid), {}).setdefault(int(raw_item), []).append(\n            int(raw_timestamp)\n        )\n    result = {\n        uid: {\n            item: np.asarray(timestamps, dtype=np.int64)\n            for item, timestamps in items.items()\n        }\n        for uid, items in nested.items()\n    }\n    log(\n        f\"loaded organic-like outcomes: rows={len(likes):,} \"\n        f\"users={len(result):,}\"\n    )\n    return result\n\n\ndef build_target_weights(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    training_counts: np.ndarray,\n    config: Config,\n) -> np.ndarray:\n    \"\"\"Build nonzero per-token weights without dropping adjacent targets.\"\"\"\n    if config.target_weighting == \"uniform\":\n        weights = np.ones(len(prepared.sequence_items), dtype=np.float32)\n    else:\n        weights = np.full(\n            len(prepared.sequence_items),\n            config.ordinary_target_weight,\n            dtype=np.float32,\n        )\n        organic_strong = (\n            (prepared.event_features[:, 0] > 0.5)\n            & (prepared.event_features[:, 1] >= 0.8)\n        )\n        weights[organic_strong] = config.organic_strong_target_weight\n        if config.target_weighting == \"discovery-graded\":\n            like_outcomes = load_organic_like_outcomes(\n                public, stage, prepared.item_ids\n            )\n            history_end = (\n                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n            )\n            horizon = config.discovery_horizon_days * base.DAY\n            grade_three = 0\n            for user_row, uid in enumerate(prepared.user_ids):\n                start = int(prepared.offsets[user_row])\n                end = int(prepared.offsets[user_row + 1])\n                if end - start < 2:\n                    continue\n                last_training_target = start + int(training_counts[user_row])\n                first_validation_target = last_training_target + 1\n                split_timestamp = (\n                    int(prepared.sequence_timestamps[first_validation_target])\n                    if first_validation_target < end\n                    else history_end\n                )\n                user_likes = like_outcomes.get(int(uid), {})\n                seen = {int(prepared.sequence_items[start])}\n                for position in range(start + 1, end):\n                    item = int(prepared.sequence_items[position])\n                    novel = item not in seen\n                    seen.add(item)\n                    if not novel:\n                        # Repeats remain training examples, but they cannot be\n                        # eligible discovery outcomes at the corresponding\n                        # cutoff and therefore keep only the ordinary weight.\n                        weights[position] = config.ordinary_target_weight\n                        continue\n                    timestamps = user_likes.get(item)\n                    if timestamps is None:\n                        continue\n                    timestamp = int(prepared.sequence_timestamps[position])\n                    upper = min(\n                        timestamp + horizon,\n                        split_timestamp\n                        if position <= last_training_target\n                        else history_end,\n                    )\n                    outcome = int(np.searchsorted(timestamps, timestamp, side=\"left\"))\n                    if outcome < len(timestamps) and int(timestamps[outcome]) < upper:\n                        weights[position] = config.organic_like_target_weight\n                        grade_three += 1\n            log(\n                f\"grade-3 first-encounter targets={grade_three:,} \"\n                f\"horizon_days={config.discovery_horizon_days}\"\n            )\n    log(\n        f\"target weighting={config.target_weighting} \"\n        f\"min={weights.min():.3f} mean={weights.mean():.3f} \"\n        f\"max={weights.max():.3f}\"\n    )\n    return weights\n\n\ndef build_dense_block(\n    prepared: SequenceData,\n    target_weights: np.ndarray,\n    users: np.ndarray,\n    window_starts: np.ndarray,\n    process_counts: np.ndarray,\n    score_starts: np.ndarray,\n    start: int,\n    steps: int,\n    config: Config,\n) -> tuple[np.ndarray, ...]:\n    \"\"\"Build one causal sequence block and mark the target rows to score.\"\"\"\n    batch_size = len(users)\n    padding_item = len(prepared.item_ids)\n    input_items = np.full((batch_size, steps), padding_item, dtype=np.uint16)\n    event_features = np.zeros((batch_size, steps, 3), dtype=np.float16)\n    activity_features = np.zeros((batch_size, steps, 4), dtype=np.float16)\n    state_ids = np.zeros((batch_size, steps), dtype=np.uint32)\n    targets = np.zeros((batch_size, steps), dtype=np.uint16)\n    weights = np.ones((batch_size, steps), dtype=np.float32)\n    scored = np.zeros((batch_size, steps), dtype=bool)\n    histories = np.full(\n        (batch_size, steps, config.bptt_steps),\n        padding_item,\n        dtype=np.uint16,\n    )\n    processed = np.zeros(batch_size, dtype=np.int32)\n\n    lengths = prepared.lengths\n    for row, user_row in enumerate(users):\n        count = min(steps, max(int(process_counts[row]) - start, 0))\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        window_start = int(window_starts[row])\n        absolute_start = window_start + start\n        positions = slice(\n            offset + absolute_start,\n            offset + absolute_start + count,\n        )\n        target_positions = slice(\n            offset + absolute_start + 1,\n            offset + absolute_start + count + 1,\n        )\n        input_items[row, :count] = prepared.sequence_items[positions]\n        event_features[row, :count] = prepared.event_features[positions]\n        activity_features[row, :count] = prepared.activity_features[positions]\n        state_ids[row, :count] = prepared.state_ids[positions]\n        targets[row, :count] = prepared.sequence_items[target_positions]\n        weights[row, :count] = target_weights[target_positions]\n        score_from = min(count, max(int(score_starts[row]) - start, 0))\n        scored[row, score_from:count] = True\n        processed[row] = count\n        user_sequence = prepared.sequence_items[\n            offset : offset + int(lengths[user_row])\n        ]\n        histories[row, :count] = history_windows(\n            user_sequence,\n            absolute_start,\n            count,\n            config.bptt_steps,\n            padding_item,\n        )\n    return (\n        input_items,\n        event_features,\n        activity_features,\n        state_ids,\n        targets,\n        scored,\n        histories,\n        processed,\n        weights,\n    )\n\n\ndef score_target_microbatches(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    sequence_vectors: torch.Tensor,\n    flat_states: np.ndarray,\n    flat_activity: np.ndarray,\n    positive_items: torch.Tensor,\n    negatives: torch.Tensor,\n    negative_weights: torch.Tensor,\n    sample_weights: np.ndarray,\n    device: torch.device,\n    backward: bool,\n) -> tuple[dict[str, float], torch.Tensor | None]:\n    \"\"\"Compute one logical block's exact BCE in bounded-memory slices.\"\"\"\n    target_count = len(positive_items)\n    total_weight = float(sample_weights.sum())\n    if total_weight <= 0:\n        raise RuntimeError(\"target block has no positive sample weight\")\n    sequence_gradient = torch.zeros_like(sequence_vectors) if backward else None\n    statistics = {\n        \"loss_sum\": 0.0,\n        \"positive_sum\": 0.0,\n        \"negative_sum\": 0.0,\n        \"pair_correct\": 0.0,\n        \"weight_sum\": 0.0,\n    }\n    for begin in range(0, target_count, config.loss_microbatch_size):\n        end = min(begin + config.loss_microbatch_size, target_count)\n        selected_states = flat_states[begin:end]\n        if backward:\n            sequence_input = (\n                sequence_vectors[begin:end].detach().requires_grad_(True)\n            )\n        else:\n            sequence_input = sequence_vectors[begin:end]\n        liked_vectors, disliked_vectors, _ = pool_explicit_states(\n            model, prepared, selected_states, device\n        )\n        counts = prepared.state_counts[selected_states]\n        numeric = np.zeros((end - begin, 6), dtype=np.float32)\n        numeric[:, :4] = flat_activity[begin:end]\n        numeric[:, 4] = np.log1p(counts[:, 0]) / 6.0\n        numeric[:, 5] = np.log1p(counts[:, 1]) / 4.0\n        query_vectors = user_queries(\n            model,\n            sequence_input,\n            liked_vectors,\n            disliked_vectors,\n            torch.from_numpy(numeric).to(device),\n        )\n        positive_vectors, negative_vectors = candidate_vectors(\n            model,\n            positive_items[begin:end],\n            negatives[begin:end],\n        )\n        positive_logits = (query_vectors * positive_vectors).sum(dim=1)\n        negative_logits = torch.einsum(\n            \"bd,bkd->bk\", query_vectors, negative_vectors\n        )\n        positive_loss = F.softplus(-positive_logits)\n        negative_loss = corrected_negative_loss(\n            negative_logits, negative_weights[begin:end], config\n        )\n        selected_weights = torch.from_numpy(\n            sample_weights[begin:end].astype(np.float32, copy=False)\n        ).to(device)\n        loss_sum = (\n            selected_weights * (positive_loss + negative_loss) / 2.0\n        ).sum()\n        if not bool(torch.isfinite(loss_sum)):\n            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n        if backward:\n            (loss_sum / total_weight).backward()\n            if sequence_input.grad is None:\n            if sequence_input.grad is None:\n                raise RuntimeError(\"sequence microbatch did not produce a gradient\")\n            sequence_gradient[begin:end] = sequence_input.grad\n        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n        statistics[\"positive_sum\"] += float(positive_logits.detach().sum().cpu())\n        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n        statistics[\"pair_correct\"] += float(\n            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n        )\n        statistics[\"weight_sum\"] += float(selected_weights.sum().detach().cpu())\n    return statistics, sequence_gradient\n\n\ndef release_accelerator_cache(device: torch.device) -> None:\n    if device.type == \"mps\":\n        torch.mps.empty_cache()\n\n\ndef run_training_epoch(\n    model: base.SequentialTwoTower,\n    optimizer: torch.optim.Optimizer,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    target_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    generator: torch.Generator,\n    device: torch.device,\n    epoch: int,\n) -> dict[str, float]:\n    model.train()\n    train_users = np.flatnonzero(target_counts > 0)\n    sorted_users = train_users[\n        np.argsort(target_counts[train_users], kind=\"stable\")\n    ]\n    groups = [\n        sorted_users[start : start + config.user_batch_size]\n        for start in range(0, len(sorted_users), config.user_batch_size)\n    ]\n    group_order = torch.randperm(len(groups), generator=generator).numpy()\n    negative_count = config.uniform_negatives + config.inbatch_negatives\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    total_positive = 0.0\n    total_negative = 0.0\n    total_pair_correct = 0.0\n    batches = 0\n    started = time.monotonic()\n\n    for group_number in group_order:\n        users = groups[int(group_number)]\n        group_counts = target_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_counts.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_counts,\n                np.zeros(len(users), dtype=np.int64),\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            optimizer.zero_grad(set_to_none=True)\n            statistics, sequence_gradient = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=True,\n            )\n            if sequence_gradient is None:\n                raise RuntimeError(\"training block omitted its sequence gradient\")\n            sequence_vectors.backward(sequence_gradient)\n            nn.utils.clip_grad_norm_(model.parameters(), config.gradient_clip)\n            optimizer.step()\n\n            count = len(positive_items)\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += count\n            total_weight += statistics[\"weight_sum\"]\n            total_positive += statistics[\"positive_sum\"]\n            total_negative += statistics[\"negative_sum\"]\n            total_pair_correct += statistics[\"pair_correct\"]\n            batches += 1\n            if batches % 25 == 0:\n                release_accelerator_cache(device)\n            if batches % 250 == 0:\n                batch_bce = statistics[\"loss_sum\"] / max(\n                    statistics[\"weight_sum\"], 1.0e-12\n                )\n                running_bce = total_loss / max(total_weight, 1.0e-12)\n                log(\n                    f\"epoch={epoch}/{config.epochs} batches={batches:,} \"\n                    f\"targets={total_targets:,} \"\n                    f\"batch_bce={batch_bce:.6f} \"\n                    f\"running_bce={running_bce:.6f} \"\n                    f\"elapsed={time.monotonic() - started:.1f}s\"\n                )\n\n    return {\n        \"epoch\": float(epoch),\n        \"loss\": total_loss / max(total_weight, 1.0e-12),\n        \"positive_logit\": total_positive / max(total_targets, 1),\n        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n        \"pair_accuracy\": total_pair_correct\n        / max(total_targets * negative_count, 1),\n        \"targets\": float(total_targets),\n        \"target_weight_sum\": total_weight,\n        \"batches\": float(batches),\n        \"seconds\": time.monotonic() - started,\n    }\n\n\n@torch.no_grad()\ndef evaluate_validation_bce(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    training_counts: np.ndarray,\n    validation_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    device: torch.device,\n) -> dict[str, float]:\n    \"\"\"Measure deterministic BCE on each user's chronological target suffix.\"\"\"\n    model.eval()\n    totals = training_counts + validation_counts\n    users_with_validation = np.flatnonzero(validation_counts > 0)\n    ordered = users_with_validation[\n        np.argsort(totals[users_with_validation], kind=\"stable\")\n    ]\n    groups = [\n        ordered[start : start + config.user_batch_size]\n        for start in range(0, len(ordered), config.user_batch_size)\n    ]\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 20_000)\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    started = time.monotonic()\n\n    for group_number, users in enumerate(groups, start=1):\n        group_totals = totals[users]\n        group_starts = training_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_totals.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_totals,\n                group_starts,\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0)\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            statistics, _ = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=False,\n            )\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += len(positive_items)\n            total_weight += statistics[\"weight_sum\"]\n        if group_number % 25 == 0:\n            release_accelerator_cache(device)\n    return {\n        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n        \"validation_targets\": float(total_targets),\n        \"validation_target_weight_sum\": total_weight,\n        \"validation_seconds\": time.monotonic() - started,\n    }\n\n\ndef snapshot_model(model: nn.Module) -> dict[str, torch.Tensor]:\n    return {\n        name: value.detach().cpu().clone()\n        for name, value in model.state_dict().items()\n    }\n\n\ndef save_epoch_checkpoint(\n    checkpoint_dir: Path,\n    epoch: int,\n    model_state: dict[str, torch.Tensor],\n    config: Config,\n    diagnostics: dict[str, float],\n    optimizer: torch.optim.Optimizer,\n    generator: torch.Generator,\n) -> Path:\n    checkpoint_dir.mkdir(parents=True, exist_ok=True)\n    path = checkpoint_dir / f\"epoch-{epoch:02d}.pt\"\n    torch.save(\n        {\n            \"epoch\": epoch,\n            \"config\": asdict(config),\n            \"diagnostics\": diagnostics,\n            \"model_state\": model_state,\n            \"optimizer_state\": optimizer.state_dict(),\n            \"generator_state\": generator.get_state(),\n        },\n        path,\n    )\n    log(f\"saved epoch checkpoint: {path}\")\n    return path\n\n\ndef train_model(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    config: Config,\n    device: torch.device,\n    checkpoint_dir: Path | None,\n    resume_checkpoint: Path | None,\n) -> tuple[base.SequentialTwoTower, list[dict[str, float]]]:\n    partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    training_counts = partition.training_counts\n    validation_counts = partition.validation_counts\n    log(\n        f\"chronological BCE window: train={int(training_counts.sum()):,} \"\n        f\"validation={int(validation_counts.sum()):,} \"\n        f\"selected={partition.selected_count:,} \"\n        f\"discarded_old_targets={int(partition.window_starts.sum()):,} \"\n        f\"all={prepared.target_count:,}\"\n    )\n    model = base.SequentialTwoTower(prepared.item_features, model_config(config)).to(\n        device\n    )\n    optimizer = torch.optim.AdamW(\n        model.parameters(), lr=config.learning_rate, weight_decay=config.weight_decay\n    )\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 10_000)\n    item_correction = build_item_correction(\n        prepared,\n        config,\n        partition.window_starts,\n        training_counts,\n    )\n    target_weights = build_target_weights(\n        public,\n        stage,\n        prepared,\n        partition.history_training_counts,\n        config,\n    )\n    known_positive_packed = (\n        build_known_positive_filter(prepared, partition.history_training_counts)\n        if config.negative_filter_scope == \"full-training-history\"\n        else None\n    )\n    history: list[dict[str, float]] = []\n    best_loss = float(\"inf\")\n    best_epoch = 0\n    best_state: dict[str, torch.Tensor] | None = None\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n            stored_config.get(\"max_validation_targets_per_user\", 0),\n        )\n        current_window_values = (\n            config.validation_fraction,\n            config.max_train_targets_per_user,\n            config.max_validation_targets_per_user,\n        )\n        objective_changed = (\n            stored_filter_scope != config.negative_filter_scope\n            or stored_target_weighting != config.target_weighting\n            or stored_weight_values != current_weight_values\n            or stored_window_values != current_window_values\n        )\n        model.load_state_dict(payload[\"model_state\"])\n        if \"optimizer_state\" in payload and not objective_changed:\n            optimizer.load_state_dict(payload[\"optimizer_state\"])\n            for group in optimizer.param_groups:\n                group[\"lr\"] = config.learning_rate\n                group[\"weight_decay\"] = config.weight_decay\n            log(f\"restored optimizer state from {resume_checkpoint}\")\n        else:\n            log(\n                f\"using a fresh AdamW optimizer after loading {resume_checkpoint}\"\n            )\n        if \"generator_state\" in payload and not objective_changed:\n            generator.set_state(payload[\"generator_state\"])\n        start_epoch = int(payload[\"epoch\"])\n        if start_epoch >= config.epochs:\n            raise RuntimeError(\n                f\"resume epoch {start_epoch} must be below --epochs {config.epochs}\"\n            )\n        prior = {\n            str(name): float(value)\n            for name, value in payload.get(\"diagnostics\", {}).items()\n        }\n        if objective_changed:\n            prior.pop(\"validation_loss\", None)\n            log(\n                \"BCE objective changed: filter \"\n                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n                \"target weighting \"\n                f\"{stored_target_weighting}->{config.target_weighting}, \"\n                f\"target window {stored_window_values}->{current_window_values}; \"\n                \"recomputing the resume checkpoint's validation BCE\"\n            )\n        if \"validation_loss\" not in prior:\n            prior.update(\n                evaluate_validation_bce(\n                    model,\n                    prepared,\n                    config,\n                    target_weights,\n                    partition.window_starts,\n                    training_counts,\n                    validation_counts,\n                    item_correction,\n                    known_positive_packed,\n                    device,\n                )\n            )\n        history.append(prior)\n        best_loss = float(prior[\"validation_loss\"])\n        best_epoch = start_epoch\n        best_state = snapshot_model(model)\n        log(\n            f\"resumed validation-BCE training: epoch={start_epoch} \"\n            f\"loss={best_loss:.6f}\"\n        )\n\n    for epoch in range(start_epoch + 1, config.epochs + 1):\n        diagnostics = run_training_epoch(\n            model,\n            optimizer,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            item_correction,\n            known_positive_packed,\n            generator,\n            device,\n            epoch,\n        )\n        validation = evaluate_validation_bce(\n            model,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            validation_counts,\n            item_correction,\n            known_positive_packed,\n            device,\n        )\n        diagnostics.update(validation)\n        history.append(diagnostics)\n        current_state = snapshot_model(model)\n        if checkpoint_dir is not None:\n            save_epoch_checkpoint(\n                checkpoint_dir,\n                epoch,\n                current_state,\n                config,\n                diagnostics,\n                optimizer,\n                generator,\n            )\n        improved = (\n            diagnostics[\"validation_loss\"]\n            < best_loss - config.early_stopping_min_delta\n        )\n        if improved:\n            best_loss = diagnostics[\"validation_loss\"]\n            best_epoch = epoch\n            best_state = current_state\n            epochs_without_improvement = 0\n            if checkpoint_dir is not None:\n                torch.save(\n                    {\n                        \"epoch\": epoch,\n                        \"config\": asdict(config),\n                        \"diagnostics\": diagnostics,\n                        \"model_state\": current_state,\n                        \"optimizer_state\": optimizer.state_dict(),\n                        \"generator_state\": generator.get_state(),\n                    },\n                    checkpoint_dir / \"best.pt\",\n                )\n        else:\n            epochs_without_improvement += 1\n        log(\n            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n            f\"pair_accuracy={diagnostics['pair_accuracy']:.3f} \"\n            f\"train_targets={int(diagnostics['targets']):,} \"\n            f\"validation_targets={int(diagnostics['validation_targets']):,} \"\n            f\"train_seconds={diagnostics['seconds']:.1f} \"\n            f\"validation_seconds={diagnostics['validation_seconds']:.1f}\"\n        )\n        release_accelerator_cache(device)\n        if epochs_without_improvement >= config.early_stopping_patience:\n            log(\n                f\"early stopping after epoch={epoch}; \"\n                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n            )\n            break\n\n    if best_state is None:\n        raise RuntimeError(\"training did not produce a valid checkpoint\")\n    model.load_state_dict(best_state)\n    model.to(device).eval()\n    log(\n        f\"restored best validation-BCE checkpoint: epoch={best_epoch} \"\n        f\"loss={best_loss:.6f}\"\n    )\n    return model, history\n\n\n@torch.inference_mode()\ndef inference_queries(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n    device: torch.device,\n    ranking_batch_size: int,\n) -> tuple[pd.DataFrame, dict[str, float]]:\n    model.eval()\n    queries = inference_queries(model, prepared, config, device)\n    item_parts: list[torch.Tensor] = []\n    for start in range(0, len(prepared.item_ids), 2_048):\n        rows = torch.arange(\n            start,\n            min(start + 2_048, len(prepared.item_ids)),\n            dtype=torch.long,\n            device=device,\n        )\n        item_parts.append(model.encode_items(rows).cpu())\n    items = torch.cat(item_parts)\n    rows: list[tuple[int, int, int]] = []\n    for start in range(0, len(eligibility.uids), ranking_batch_size):\n        end = min(start + ranking_batch_size, len(eligibility.uids))\n        scores = queries[start:end] @ items.T\n        eligible = np.unpackbits(\n            eligibility.packed[start:end],\n            axis=1,\n            count=len(prepared.item_ids),\n            bitorder=\"little\",\n        ).astype(bool, copy=False)\n        scores.masked_fill_(~torch.from_numpy(eligible), -torch.inf)\n        selected = torch.topk(scores, k=base.TOP_N, dim=1).indices.numpy()\n        for local_row, columns in enumerate(selected):\n            uid = int(eligibility.uids[start + local_row])\n            rows.extend(\n                (uid, int(prepared.item_ids[column]), rank)\n                for rank, column in enumerate(columns, start=1)\n            )\n        if end == len(eligibility.uids) or end % 1_024 == 0:\n            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n    query_norm = torch.linalg.vector_norm(queries, dim=1).numpy()\n    item_norm = torch.linalg.vector_norm(items, dim=1).numpy()\n    diagnostics = {\n        \"query_norm_mean\": float(query_norm.mean()),\n        \"query_norm_std\": float(query_norm.std()),\n        \"item_norm_mean\": float(item_norm.mean()),\n        \"item_norm_std\": float(item_norm.std()),\n    }\n    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n\n\ndef write_ranking(frame: pd.DataFrame, output: Path) -> None:\n    output.parent.mkdir(parents=True, exist_ok=True)\n    if output.suffix == \".parquet\":\n        frame.to_parquet(output, index=False, compression=\"zstd\")\n    elif output.suffix == \".csv\":\n        frame.to_csv(output, index=False)\n    else:\n        raise ValueError(\"--output must end in .parquet or .csv\")\n\n\ndef main() -> int:\n    parser = argparse.ArgumentParser(description=__doc__)\n    parser.add_argument(\n        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n    )\n    parser.add_argument(\"--output\", type=Path, required=True)\n    parser.add_argument(\"--public-dir\", type=Path, required=True)\n    parser.add_argument(\"--prepared-cache\", type=Path)\n    parser.add_argument(\"--device\", choices=(\"cpu\", \"mps\"), default=\"cpu\")\n    parser.add_argument(\"--threads\", type=int, default=8)\n    parser.add_argument(\"--bptt-steps\", type=int, default=Config.bptt_steps)\n    parser.add_argument(\n        \"--user-batch-size\", type=int, default=Config.user_batch_size\n    )\n    parser.add_argument(\"--epochs\", type=int, default=Config.epochs)\n    parser.add_argument(\"--learning-rate\", type=float, default=Config.learning_rate)\n    parser.add_argument(\n        \"--loss-microbatch-size\",\n        type=int,\n        default=Config.loss_microbatch_size,\n    )\n    parser.add_argument(\n        \"--negative-filter-scope\",\n        choices=(\"full-training-history\", \"last-100\"),\n        default=Config.negative_filter_scope,\n    )\n    parser.add_argument(\n        \"--target-weighting\",\n        choices=(\"discovery-graded\", \"organic-strong\", \"uniform\"),\n        default=Config.target_weighting,\n    )\n    parser.add_argument(\n        \"--ordinary-target-weight\",\n        type=float,\n        default=Config.ordinary_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-strong-target-weight\",\n        type=float,\n        default=Config.organic_strong_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-like-target-weight\",\n        type=float,\n        default=Config.organic_like_target_weight,\n    )\n    parser.add_argument(\n        \"--discovery-horizon-days\",\n        type=int,\n        default=Config.discovery_horizon_days,\n    )\n    parser.add_argument(\n        \"--validation-fraction\",\n        type=float,\n        default=Config.validation_fraction,\n    )\n    parser.add_argument(\n        \"--max-train-targets-per-user\",\n        type=int,\n        default=Config.max_train_targets_per_user,\n        help=\"retain this many recent pre-validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--max-validation-targets-per-user\",\n        type=int,\n        default=Config.max_validation_targets_per_user,\n        help=\"retain this many final validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--early-stopping-patience\",\n        type=int,\n        default=Config.early_stopping_patience,\n    )\n    parser.add_argument(\n        \"--early-stopping-min-delta\",\n        type=float,\n        default=Config.early_stopping_min_delta,\n    )\n    parser.add_argument(\"--checkpoint-dir\", type=Path)\n    parser.add_argument(\"--resume-checkpoint\", type=Path)\n    parser.add_argument(\"--seed\", type=int, default=Config.seed)\n    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n    parser.add_argument(\"--prepare-only\", action=\"store_true\")\n    args = parser.parse_args()\n\n    if args.threads < 1 or args.bptt_steps < 2 or args.user_batch_size < 1:\n        parser.error(\"threads, BPTT steps, and user batch size must be positive\")\n    if (\n        args.epochs < 1\n        or args.learning_rate <= 0\n        or args.loss_microbatch_size < 1\n        or args.early_stopping_patience < 1\n        or args.early_stopping_min_delta < 0\n        or args.ordinary_target_weight <= 0\n        or args.organic_strong_target_weight <= 0\n        or args.organic_like_target_weight <= 0\n        or args.discovery_horizon_days < 1\n        or args.max_train_targets_per_user < 0\n        or args.max_validation_targets_per_user < 0\n    ):\n        parser.error(\"training counts, learning rate, and patience are invalid\")\n    if not 0.0 < args.validation_fraction < 1.0:\n        parser.error(\"validation fraction must be strictly between zero and one\")\n    public = args.public_dir.resolve()\n    if not (public / \"data\" / \"candidate_catalog.parquet\").is_file():\n        parser.error(f\"public task data not found under {public}\")\n    config = Config(\n        bptt_steps=args.bptt_steps,\n        user_batch_size=args.user_batch_size,\n        epochs=args.epochs,\n        learning_rate=args.learning_rate,\n        loss_microbatch_size=args.loss_microbatch_size,\n        negative_filter_scope=args.negative_filter_scope,\n        target_weighting=args.target_weighting,\n        ordinary_target_weight=args.ordinary_target_weight,\n        organic_strong_target_weight=args.organic_strong_target_weight,\n        organic_like_target_weight=args.organic_like_target_weight,\n        discovery_horizon_days=args.discovery_horizon_days,\n        validation_fraction=args.validation_fraction,\n        max_train_targets_per_user=args.max_train_targets_per_user,\n        max_validation_targets_per_user=args.max_validation_targets_per_user,\n        early_stopping_patience=args.early_stopping_patience,\n        early_stopping_min_delta=args.early_stopping_min_delta,\n        seed=args.seed,\n    )\n    torch.set_num_threads(args.threads)\n    torch.set_num_interop_threads(1)\n    seed_everything(config.seed)\n    device = torch.device(args.device)\n    if device.type == \"mps\" and not torch.backends.mps.is_available():\n        parser.error(\"MPS was requested but is unavailable\")\n\n    started = time.monotonic()\n    prepared, eligibility = load_or_prepare(\n        public,\n        args.stage,\n        config,\n        args.prepared_cache.resolve() if args.prepared_cache else None,\n    )\n    target_partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    if args.prepare_only:\n        print(\n            json.dumps(\n                {\n                    \"stage\": args.stage,\n                    \"sequence_users\": len(prepared.user_ids),\n                    \"sequence_tokens\": len(prepared.sequence_items),\n                    \"next_item_targets\": prepared.target_count,\n                    \"selected_training_targets\": int(\n                        target_partition.training_counts.sum()\n                    ),\n                    \"selected_validation_targets\": int(\n                        target_partition.validation_counts.sum()\n                    ),\n                    \"discarded_old_targets\": int(\n                        target_partition.window_starts.sum()\n                    ),\n                    \"target_users\": len(eligibility.uids),\n                    \"runtime_seconds\": round(time.monotonic() - started, 3),\n                    \"config\": asdict(config),\n                },\n                indent=2,\n            )\n        )\n        return 0\n\n    model, training_history = train_model(\n        public,\n        args.stage,\n        prepared,\n        config,\n        device,\n        args.checkpoint_dir.resolve() if args.checkpoint_dir else None,\n        args.resume_checkpoint.resolve() if args.resume_checkpoint else None,\n    )\n    ranking, embedding_diagnostics = rank_candidates(\n        model,\n        prepared,\n        eligibility,\n        config,\n        device,\n        args.ranking_batch_size,\n    )\n    write_ranking(ranking, args.output.resolve())\n    print(\n        json.dumps(\n            {\n                \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n                \"stage\": args.stage,\n                \"output\": str(args.output.resolve()),\n                \"rows\": len(ranking),\n                \"users\": int(ranking.uid.nunique()),\n                \"runtime_seconds\": round(time.monotonic() - started, 3),\n                \"public_inputs_only\": True,\n                \"architecture\": {\n                    \"family\": \"pure-windowed-sequence-two-tower\",\n                    \"sequence_training\": (\n                        \"every-adjacent-target-within-recent-chronological-window\"\n                    ),\n                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n                    \"bptt_hidden_state\": \"carried-and-detached\",\n                    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n                    \"user_id_embedding\": False,\n                    \"user_mlp\": \"582-512-256-192\",\n                    \"item_mlp\": \"196-512-256-192\",\n                    \"normalization\": \"none\",\n                    \"score\": \"raw-dot-product\",\n                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n                    \"negative_sampling\": (\n                        \"24-uniform-plus-8-propensity-corrected-inbatch\"\n                    ),\n                    \"false_negative_filter\": config.negative_filter_scope,\n                    \"target_weighting\": config.target_weighting,\n                },\n                \"config\": asdict(config),\n                \"sequence_tokens\": len(prepared.sequence_items),\n                \"all_next_item_targets\": prepared.target_count,\n                \"selected_training_targets\": int(\n                    target_partition.training_counts.sum()\n                ),\n                \"selected_validation_targets\": int(\n                    target_partition.validation_counts.sum()\n                ),\n                \"discarded_old_targets\": int(target_partition.window_starts.sum()),\n                \"training_history\": training_history,\n                \"embedding_diagnostics\": embedding_diagnostics,\n                \"torch_version\": torch.__version__,\n                \"device\": str(device),\n            },\n            indent=2,\n        )\n    )\n    return 0\n",
              "exit_code": 0,
              "duration": {
                "secs": 0,
                "nanos": 5870
              },
              "formatted_output": "Warning: truncated output (original token count: 12540)\nTotal output lines: 1328\n\n    )\n\n\ndef event_sequence(\n    model: base.SequentialTwoTower,\n    items: torch.Tensor,\n    features: torch.Tensor,\n    hidden: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    inputs = torch.cat([model.context_embedding(items), features], dim=-1)\n    projected = model.event_projection(inputs)\n    return model.sequence_encoder(projected, hidden)\n\n\ndef pool_explicit_states(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    state_ids: np.ndarray,\n    device: torch.device,\n) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:\n    unique_states, inverse = np.unique(state_ids, return_inverse=True)\n    liked_items = torch.from_numpy(\n        prepared.liked_states[unique_states].astype(np.int64)\n    ).to(device)\n    disliked_items = torch.from_numpy(\n        prepared.disliked_states[unique_states].astype(np.int64)\n    ).to(device)\n    liked_vectors = model._mean_context_channel(liked_items)\n    disliked_vectors = model._mean_context_channel(disliked_items)\n    inverse_rows = torch.from_numpy(inverse.astype(np.int64)).to(device)\n    counts = prepared.state_counts[state_ids]\n    return (\n        liked_vectors[inverse_rows],\n        disliked_vectors[inverse_rows],\n        torch.from_numpy(counts.astype(np.float32)).to(device),\n    )\n\n\ndef user_queries(\n    model: base.SequentialTwoTower,\n    sequence_vectors: torch.Tensor,\n    liked_vectors: torch.Tensor,\n    disliked_vectors: torch.Tensor,\n    user_features: torch.Tensor,\n) -> torch.Tensor:\n    return model.user_tower(\n        torch.cat(\n            [sequence_vectors, liked_vectors, disliked_vectors, user_features],\n            dim=1,\n        )\n    )\n\n\ndef candidate_vectors(\n    model: base.SequentialTwoTower,\n    positives: torch.Tensor,\n    negatives: torch.Tensor,\n) -> tuple[torch.Tensor, torch.Tensor]:\n    all_items = torch.cat([positives, negatives.reshape(-1)])\n    unique_items, inverse = torch.unique(all_items, return_inverse=True)\n    encoded = model.encode_items(unique_items)\n    positive_vectors = encoded[inverse[: len(positives)]]\n    negative_vectors = encoded[inverse[len(positives) :]].reshape(\n        len(positives), negatives.shape[1], -1\n    )\n    return positive_vectors, negative_vectors\n\n\ndef history_windows(\n    sequence: np.ndarray,\n    start: int,\n    count: int,\n    width: int,\n    padding_item: int,\n) -> np.ndarray:\n    base_start = max(0, start - width + 1)\n    segment = sequence[base_start : start + count]\n    padded = np.concatenate(\n        [np.full(width - 1, padding_item, dtype=np.uint16), segment]\n    )\n    windows = np.lib.stride_tricks.sliding_window_view(padded, width)\n    offset = start - base_start\n    return windows[offset : offset + count].copy()\n\n\ndef corrected_negative_loss(\n    logits: torch.Tensor,\n    correction: torch.Tensor,\n    config: Config,\n) -> torch.Tensor:\n    raw = F.softplus(logits)\n    total = config.uniform_negatives + config.inbatch_negatives\n    result = torch.zeros(len(logits), device=logits.device)\n    if config.uniform_negatives:\n        result += config.uniform_negatives * raw[\n            :, : config.uniform_negatives\n        ].mean(dim=1)\n    if config.inbatch_negatives:\n        selected = slice(config.uniform_negatives, total)\n        weights = correction[:, selected]\n        result += config.inbatch_negatives * (\n            (raw[:, selected] * weights).sum(dim=1)\n            / weights.sum(dim=1).clamp_min(1.0e-6)\n        )\n    return result / total\n\n\ndef retained_target_window_starts(\n    total_targets: np.ndarray,\n    validation_counts: np.ndarray,\n    training_counts: np.ndarray,\n) -> np.ndarray:\n    \"\"\"Return the discarded prefix before the retained chronological suffix.\"\"\"\n    training_region_ends = total_targets - validation_counts\n    window_starts = training_region_ends - training_counts\n    if (\n        np.any(window_starts < 0)\n        or np.any(training_counts < 0)\n        or np.any(validation_counts < 0)\n    ):\n        raise RuntimeError(\"chronological target partition produced negative counts\")\n    if not np.array_equal(\n        window_starts + training_counts + validation_counts, total_targets\n    ):\n        raise RuntimeError(\"chronological target window is not a final contiguous suffix\")\n    return window_starts\n\n\ndef chronological_target_partition(\n    prepared: SequenceData,\n    validation_fraction: float,\n    max_train_targets_per_user: int,\n    max_validation_targets_per_user: int,\n) -> TargetPartition:\n    \"\"\"Select a recent contiguous window with a final out-of-time BCE suffix.\"\"\"\n    totals = np.maximum(prepared.lengths - 1, 0).astype(np.int64)\n    validation = np.floor(totals * validation_fraction).astype(np.int64)\n    validation[(totals >= 2) & (validation == 0)] = 1\n    if max_validation_targets_per_user:\n        validation = np.minimum(validation, max_validation_targets_per_user)\n\n    history_training = totals - validation\n    training = history_training.copy()\n    if max_train_targets_per_user:\n        training = np.minimum(training, max_train_targets_per_user)\n    window_starts = retained_target_window_starts(totals, validation, training)\n    return TargetPartition(\n        window_starts=window_starts,\n        training_counts=training,\n        validation_counts=validation,\n        history_training_counts=history_training,\n    )\n\n\ndef load_organic_like_outcomes(\n    public: Path, stage: str, item_ids: np.ndarray\n) -> dict[int, dict[int, np.ndarray]]:\n    \"\"\"Load mapped organic-like timestamps from public fitting history.\"\"\"\n    prefixes = (\"train\",) if stage == \"validation\" else (\"train\", \"val\")\n    frames = [\n        pd.read_parquet(\n            public / \"data\" / f\"{prefix}_likes.parquet\",\n            columns=[\"uid\", \"timestamp\", \"item_id\", \"is_organic\"],\n        )\n        for prefix in prefixes\n    ]\n    likes = pd.concat(frames, ignore_index=True)\n    likes = likes[likes.is_organic == 1].copy()\n    mapped = pd.Index(item_ids).get_indexer(\n        likes.item_id.to_numpy(dtype=np.int64)\n    )\n    likes = likes.loc[mapped >= 0, [\"uid\", \"timestamp\"]].copy()\n    likes[\"item\"] = mapped[mapped >= 0].astype(np.int32, copy=False)\n    likes = likes.sort_values([\"uid\", \"item\", \"timestamp\"], kind=\"stable\")\n    nested: dict[int, dict[int, list[int]]] = {}\n    for raw_uid, raw_timestamp, raw_item in likes.itertuples(\n        index=False, name=None\n    ):\n        nested.setdefault(int(raw_uid), {}).setdefault(int(raw_item), []).append(\n            int(raw_timestamp)\n        )\n    result = {\n        uid: {\n            item: np.asarray(timestamps, dtype=np.int64)\n            for item, timestamps in items.items()\n        }\n        for uid, items in nested.items()\n    }\n    log(\n        f\"loaded organic-like outcomes: rows={len(likes):,} \"\n        f\"users={len(result):,}\"\n    )\n    return result\n\n\ndef build_target_weights(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    training_counts: np.ndarray,\n    config: Config,\n) -> np.ndarray:\n    \"\"\"Build nonzero per-token weights without dropping adjacent targets.\"\"\"\n    if config.target_weighting == \"uniform\":\n        weights = np.ones(len(prepared.sequence_items), dtype=np.float32)\n    else:\n        weights = np.full(\n            len(prepared.sequence_items),\n            config.ordinary_target_weight,\n            dtype=np.float32,\n        )\n        organic_strong = (\n            (prepared.event_features[:, 0] > 0.5)\n            & (prepared.event_features[:, 1] >= 0.8)\n        )\n        weights[organic_strong] = config.organic_strong_target_weight\n        if config.target_weighting == \"discovery-graded\":\n            like_outcomes = load_organic_like_outcomes(\n                public, stage, prepared.item_ids\n            )\n            history_end = (\n                base.TRAIN_END if stage == \"validation\" else base.VALIDATION_END\n            )\n            horizon = config.discovery_horizon_days * base.DAY\n            grade_three = 0\n            for user_row, uid in enumerate(prepared.user_ids):\n                start = int(prepared.offsets[user_row])\n                end = int(prepared.offsets[user_row + 1])\n                if end - start < 2:\n                    continue\n                last_training_target = start + int(training_counts[user_row])\n                first_validation_target = last_training_target + 1\n                split_timestamp = (\n                    int(prepared.sequence_timestamps[first_validation_target])\n                    if first_validation_target < end\n                    else history_end\n                )\n                user_likes = like_outcomes.get(int(uid), {})\n                seen = {int(prepared.sequence_items[start])}\n                for position in range(start + 1, end):\n                    item = int(prepared.sequence_items[position])\n                    novel = item not in seen\n                    seen.add(item)\n                    if not novel:\n                        # Repeats remain training examples, but they cannot be\n                        # eligible discovery outcomes at the corresponding\n                        # cutoff and therefore keep only the ordinary weight.\n                        weights[position] = config.ordinary_target_weight\n                        continue\n                    timestamps = user_likes.get(item)\n                    if timestamps is None:\n                        continue\n                    timestamp = int(prepared.sequence_timestamps[position])\n                    upper = min(\n                        timestamp + horizon,\n                        split_timestamp\n                        if position <= last_training_target\n                        else history_end,\n                    )\n                    outcome = int(np.searchsorted(timestamps, timestamp, side=\"left\"))\n                    if outcome < len(timestamps) and int(timestamps[outcome]) < upper:\n                        weights[position] = config.organic_like_target_weight\n                        grade_three += 1\n            log(\n                f\"grade-3 first-encounter targets={grade_three:,} \"\n                f\"horizon_days={config.discovery_horizon_days}\"\n            )\n    log(\n        f\"target weighting={config.target_weighting} \"\n        f\"min={weights.min():.3f} mean={weights.mean():.3f} \"\n        f\"max={weights.max():.3f}\"\n    )\n    return weights\n\n\ndef build_dense_block(\n    prepared: SequenceData,\n    target_weights: np.ndarray,\n    users: np.ndarray,\n    window_starts: np.ndarray,\n    process_counts: np.ndarray,\n    score_starts: np.ndarray,\n    start: int,\n    steps: int,\n    config: Config,\n) -> tuple[np.ndarray, ...]:\n    \"\"\"Build one causal sequence block and mark the target rows to score.\"\"\"\n    batch_size = len(users)\n    padding_item = len(prepared.item_ids)\n    input_items = np.full((batch_size, steps), padding_item, dtype=np.uint16)\n    event_features = np.zeros((batch_size, steps, 3), dtype=np.float16)\n    activity_features = np.zeros((batch_size, steps, 4), dtype=np.float16)\n    state_ids = np.zeros((batch_size, steps), dtype=np.uint32)\n    targets = np.zeros((batch_size, steps), dtype=np.uint16)\n    weights = np.ones((batch_size, steps), dtype=np.float32)\n    scored = np.zeros((batch_size, steps), dtype=bool)\n    histories = np.full(\n        (batch_size, steps, config.bptt_steps),\n        padding_item,\n        dtype=np.uint16,\n    )\n    processed = np.zeros(batch_size, dtype=np.int32)\n\n    lengths = prepared.lengths\n    for row, user_row in enumerate(users):\n        count = min(steps, max(int(process_counts[row]) - start, 0))\n        if not count:\n            continue\n        offset = int(prepared.offsets[user_row])\n        window_start = int(window_starts[row])\n        absolute_start = window_start + start\n        positions = slice(\n            offset + absolute_start,\n            offset + absolute_start + count,\n        )\n        target_positions = slice(\n            offset + absolute_start + 1,\n            offset + absolute_start + count + 1,\n        )\n        input_items[row, :count] = prepared.sequence_items[positions]\n        event_features[row, :count] = prepared.event_features[positions]\n        activity_features[row, :count] = prepared.activity_features[positions]\n        state_ids[row, :count] = prepared.state_ids[positions]\n        targets[row, :count] = prepared.sequence_items[target_positions]\n        weights[row, :count] = target_weights[target_positions]\n        score_from = min(count, max(int(score_starts[row]) - start, 0))\n        scored[row, score_from:count] = True\n        processed[row] = count\n        user_sequence = prepared.sequence_items[\n            offset : offset + int(lengths[user_row])\n        ]\n        histories[row, :count] = history_windows(\n            user_sequence,\n            absolute_start,\n            count,\n            config.bptt_steps,\n            padding_item,\n        )\n    return (\n        input_items,\n        event_features,\n        activity_features,\n        state_ids,\n        targets,\n        scored,\n        histories,\n        processed,\n        weights,\n    )\n\n\ndef score_target_microbatches(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    sequence_vectors: torch.Tensor,\n    flat_states: np.ndarray,\n    flat_activity: np.ndarray,\n    positive_items: torch.Tensor,\n    negatives: torch.Tensor,\n    negative_weights: torch.Tensor,\n    sample_weights: np.ndarray,\n    device: torch.device,\n    backward: bool,\n) -> tuple[dict[str, float], torch.Tensor | None]:\n    \"\"\"Compute one logical block's exact BCE in bounded-memory slices.\"\"\"\n    target_count = len(positive_items)\n    total_weight = float(sample_weights.sum())\n    if total_weight <= 0:\n        raise RuntimeError(\"target block has no positive sample weight\")\n    sequence_gradient = torch.zeros_like(sequence_vectors) if backward else None\n    statistics = {\n        \"loss_sum\": 0.0,\n        \"positive_sum\": 0.0,\n        \"negative_sum\": 0.0,\n        \"pair_correct\": 0.0,\n        \"weight_sum\": 0.0,\n    }\n    for begin in range(0, target_count, config.loss_microbatch_size):\n        end = min(begin + config.loss_microbatch_size, target_count)\n        selected_states = flat_states[begin:end]\n        if backward:\n            sequence_input = (\n                sequence_vectors[begin:end].detach().requires_grad_(True)\n            )\n        else:\n            sequence_input = sequence_vectors[begin:end]\n        liked_vectors, disliked_vectors, _ = pool_explicit_states(\n            model, prepared, selected_states, device\n        )\n        counts = prepared.state_counts[selected_states]\n        numeric = np.zeros((end - begin, 6), dtype=np.float32)\n        numeric[:, :4] = flat_activity[begin:end]\n        numeric[:, 4] = np.log1p(counts[:, 0]) / 6.0\n        numeric[:, 5] = np.log1p(counts[:, 1]) / 4.0\n        query_vectors = user_queries(\n            model,\n            sequence_input,\n            liked_vectors,\n            disliked_vectors,\n            torch.from_numpy(numeric).to(device),\n        )\n        positive_vectors, negative_vectors = candidate_vectors(\n            model,\n            positive_items[begin:end],\n            negatives[begin:end],\n        )\n        positive_logits = (query_vectors * positive_vectors).sum(dim=1)\n        negative_logits = torch.einsum(\n            \"bd,bkd->bk\", query_vectors, negative_vectors\n        )\n        positive_loss = F.softplus(-positive_logits)\n        negative_loss = corrected_negative_loss(\n            negative_logits, negative_weights[begin:end], config\n        )\n        selected_weights = torch.from_numpy(\n            sample_weights[begin:end].astype(np.float32, copy=False)\n        ).to(device)\n        loss_sum = (\n            selected_weights * (positive_loss + negative_loss) / 2.0\n        ).sum()\n        if not bool(torch.isfinite(loss_sum)):\n            raise RuntimeError(\"dense next-item training produced non-finite loss\")\n        if backward:\n            (loss_sum / total_weight).backward()\n            if sequence_input.grad is None:\n            if sequence_input.grad is None:\n                raise RuntimeError(\"sequence microbatch did not produce a gradient\")\n            sequence_gradient[begin:end] = sequence_input.grad\n        statistics[\"loss_sum\"] += float(loss_sum.detach().cpu())\n        statistics[\"positive_sum\"] += float(positive_logits.detach().sum().cpu())\n        statistics[\"negative_sum\"] += float(negative_logits.detach().sum().cpu())\n        statistics[\"pair_correct\"] += float(\n            (positive_logits.detach()[:, None] > negative_logits.detach()).sum().cpu()\n        )\n        statistics[\"weight_sum\"] += float(selected_weights.sum().detach().cpu())\n    return statistics, sequence_gradient\n\n\ndef release_accelerator_cache(device: torch.device) -> None:\n    if device.type == \"mps\":\n        torch.mps.empty_cache()\n\n\ndef run_training_epoch(\n    model: base.SequentialTwoTower,\n    optimizer: torch.optim.Optimizer,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    target_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    generator: torch.Generator,\n    device: torch.device,\n    epoch: int,\n) -> dict[str, float]:\n    model.train()\n    train_users = np.flatnonzero(target_counts > 0)\n    sorted_users = train_users[\n        np.argsort(target_counts[train_users], kind=\"stable\")\n    ]\n    groups = [\n        sorted_users[start : start + config.user_batch_size]\n        for start in range(0, len(sorted_users), config.user_batch_size)\n    ]\n    group_order = torch.randperm(len(groups), generator=generator).numpy()\n    negative_count = config.uniform_negatives + config.inbatch_negatives\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    total_positive = 0.0\n    total_negative = 0.0\n    total_pair_correct = 0.0\n    batches = 0\n    started = time.monotonic()\n\n    for group_number in group_order:\n        users = groups[int(group_number)]\n        group_counts = target_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_counts.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_counts,\n                np.zeros(len(users), dtype=np.int64),\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n …2540 tokens truncated…\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n            stored_config.get(\"max_validation_targets_per_user\", 0),\n        )\n        current_window_values = (\n            config.validation_fraction,\n            config.max_train_targets_per_user,\n            config.max_validation_targets_per_user,\n        )\n        objective_changed = (\n            stored_filter_scope != config.negative_filter_scope\n            or stored_target_weighting != config.target_weighting\n            or stored_weight_values != current_weight_values\n            or stored_window_values != current_window_values\n        )\n        model.load_state_dict(payload[\"model_state\"])\n        if \"optimizer_state\" in payload and not objective_changed:\n            optimizer.load_state_dict(payload[\"optimizer_state\"])\n            for group in optimizer.param_groups:\n                group[\"lr\"] = config.learning_rate\n                group[\"weight_decay\"] = config.weight_decay\n            log(f\"restored optimizer state from {resume_checkpoint}\")\n        else:\n            log(\n                f\"using a fresh AdamW optimizer after loading {resume_checkpoint}\"\n            )\n        if \"generator_state\" in payload and not objective_changed:\n            generator.set_state(payload[\"generator_state\"])\n        start_epoch = int(payload[\"epoch\"])\n        if start_epoch >= config.epochs:\n            raise RuntimeError(\n                f\"resume epoch {start_epoch} must be below --epochs {config.epochs}\"\n            )\n        prior = {\n            str(name): float(value)\n            for name, value in payload.get(\"diagnostics\", {}).items()\n        }\n        if objective_changed:\n            prior.pop(\"validation_loss\", None)\n            log(\n                \"BCE objective changed: filter \"\n                f\"{stored_filter_scope}->{config.negative_filter_scope}, \"\n                \"target weighting \"\n                f\"{stored_target_weighting}->{config.target_weighting}, \"\n                f\"target window {stored_window_values}->{current_window_values}; \"\n                \"recomputing the resume checkpoint's validation BCE\"\n            )\n        if \"validation_loss\" not in prior:\n            prior.update(\n                evaluate_validation_bce(\n                    model,\n                    prepared,\n                    config,\n                    target_weights,\n                    partition.window_starts,\n                    training_counts,\n                    validation_counts,\n                    item_correction,\n                    known_positive_packed,\n                    device,\n                )\n            )\n        history.append(prior)\n        best_loss = float(prior[\"validation_loss\"])\n        best_epoch = start_epoch\n        best_state = snapshot_model(model)\n        log(\n            f\"resumed validation-BCE training: epoch={start_epoch} \"\n            f\"loss={best_loss:.6f}\"\n        )\n\n    for epoch in range(start_epoch + 1, config.epochs + 1):\n        diagnostics = run_training_epoch(\n            model,\n            optimizer,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            item_correction,\n            known_positive_packed,\n            generator,\n            device,\n            epoch,\n        )\n        validation = evaluate_validation_bce(\n            model,\n            prepared,\n            config,\n            target_weights,\n            partition.window_starts,\n            training_counts,\n            validation_counts,\n            item_correction,\n            known_positive_packed,\n            device,\n        )\n        diagnostics.update(validation)\n        history.append(diagnostics)\n        current_state = snapshot_model(model)\n        if checkpoint_dir is not None:\n            save_epoch_checkpoint(\n                checkpoint_dir,\n                epoch,\n                current_state,\n                config,\n                diagnostics,\n                optimizer,\n                generator,\n            )\n        improved = (\n            diagnostics[\"validation_loss\"]\n            < best_loss - config.early_stopping_min_delta\n        )\n        if improved:\n            best_loss = diagnostics[\"validation_loss\"]\n            best_epoch = epoch\n            best_state = current_state\n            epochs_without_improvement = 0\n            if checkpoint_dir is not None:\n                torch.save(\n                    {\n                        \"epoch\": epoch,\n                        \"config\": asdict(config),\n                        \"diagnostics\": diagnostics,\n                        \"model_state\": current_state,\n                        \"optimizer_state\": optimizer.state_dict(),\n                        \"generator_state\": generator.get_state(),\n                    },\n                    checkpoint_dir / \"best.pt\",\n                )\n        else:\n            epochs_without_improvement += 1\n        log(\n            f\"epoch={epoch}/{config.epochs} train_loss={diagnostics['loss']:.5f} \"\n            f\"validation_loss={diagnostics['validation_loss']:.5f} \"\n            f\"pair_accuracy={diagnostics['pair_accuracy']:.3f} \"\n            f\"train_targets={int(diagnostics['targets']):,} \"\n            f\"validation_targets={int(diagnostics['validation_targets']):,} \"\n            f\"train_seconds={diagnostics['seconds']:.1f} \"\n            f\"validation_seconds={diagnostics['validation_seconds']:.1f}\"\n        )\n        release_accelerator_cache(device)\n        if epochs_without_improvement >= config.early_stopping_patience:\n            log(\n                f\"early stopping after epoch={epoch}; \"\n                f\"best_epoch={best_epoch} best_validation_loss={best_loss:.6f}\"\n            )\n            break\n\n    if best_state is None:\n        raise RuntimeError(\"training did not produce a valid checkpoint\")\n    model.load_state_dict(best_state)\n    model.to(device).eval()\n    log(\n        f\"restored best validation-BCE checkpoint: epoch={best_epoch} \"\n        f\"loss={best_loss:.6f}\"\n    )\n    return model, history\n\n\n@torch.inference_mode()\ndef inference_queries(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n    device: torch.device,\n    ranking_batch_size: int,\n) -> tuple[pd.DataFrame, dict[str, float]]:\n    model.eval()\n    queries = inference_queries(model, prepared, config, device)\n    item_parts: list[torch.Tensor] = []\n    for start in range(0, len(prepared.item_ids), 2_048):\n        rows = torch.arange(\n            start,\n            min(start + 2_048, len(prepared.item_ids)),\n            dtype=torch.long,\n            device=device,\n        )\n        item_parts.append(model.encode_items(rows).cpu())\n    items = torch.cat(item_parts)\n    rows: list[tuple[int, int, int]] = []\n    for start in range(0, len(eligibility.uids), ranking_batch_size):\n        end = min(start + ranking_batch_size, len(eligibility.uids))\n        scores = queries[start:end] @ items.T\n        eligible = np.unpackbits(\n            eligibility.packed[start:end],\n            axis=1,\n            count=len(prepared.item_ids),\n            bitorder=\"little\",\n        ).astype(bool, copy=False)\n        scores.masked_fill_(~torch.from_numpy(eligible), -torch.inf)\n        selected = torch.topk(scores, k=base.TOP_N, dim=1).indices.numpy()\n        for local_row, columns in enumerate(selected):\n            uid = int(eligibility.uids[start + local_row])\n            rows.extend(\n                (uid, int(prepared.item_ids[column]), rank)\n                for rank, column in enumerate(columns, start=1)\n            )\n        if end == len(eligibility.uids) or end % 1_024 == 0:\n            log(f\"ranked users={end:,}/{len(eligibility.uids):,}\")\n    query_norm = torch.linalg.vector_norm(queries, dim=1).numpy()\n    item_norm = torch.linalg.vector_norm(items, dim=1).numpy()\n    diagnostics = {\n        \"query_norm_mean\": float(query_norm.mean()),\n        \"query_norm_std\": float(query_norm.std()),\n        \"item_norm_mean\": float(item_norm.mean()),\n        \"item_norm_std\": float(item_norm.std()),\n    }\n    return pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]), diagnostics\n\n\ndef write_ranking(frame: pd.DataFrame, output: Path) -> None:\n    output.parent.mkdir(parents=True, exist_ok=True)\n    if output.suffix == \".parquet\":\n        frame.to_parquet(output, index=False, compression=\"zstd\")\n    elif output.suffix == \".csv\":\n        frame.to_csv(output, index=False)\n    else:\n        raise ValueError(\"--output must end in .parquet or .csv\")\n\n\ndef main() -> int:\n    parser = argparse.ArgumentParser(description=__doc__)\n    parser.add_argument(\n        \"--stage\", choices=(\"validation\", \"submission\"), default=\"validation\"\n    )\n    parser.add_argument(\"--output\", type=Path, required=True)\n    parser.add_argument(\"--public-dir\", type=Path, required=True)\n    parser.add_argument(\"--prepared-cache\", type=Path)\n    parser.add_argument(\"--device\", choices=(\"cpu\", \"mps\"), default=\"cpu\")\n    parser.add_argument(\"--threads\", type=int, default=8)\n    parser.add_argument(\"--bptt-steps\", type=int, default=Config.bptt_steps)\n    parser.add_argument(\n        \"--user-batch-size\", type=int, default=Config.user_batch_size\n    )\n    parser.add_argument(\"--epochs\", type=int, default=Config.epochs)\n    parser.add_argument(\"--learning-rate\", type=float, default=Config.learning_rate)\n    parser.add_argument(\n        \"--loss-microbatch-size\",\n        type=int,\n        default=Config.loss_microbatch_size,\n    )\n    parser.add_argument(\n        \"--negative-filter-scope\",\n        choices=(\"full-training-history\", \"last-100\"),\n        default=Config.negative_filter_scope,\n    )\n    parser.add_argument(\n        \"--target-weighting\",\n        choices=(\"discovery-graded\", \"organic-strong\", \"uniform\"),\n        default=Config.target_weighting,\n    )\n    parser.add_argument(\n        \"--ordinary-target-weight\",\n        type=float,\n        default=Config.ordinary_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-strong-target-weight\",\n        type=float,\n        default=Config.organic_strong_target_weight,\n    )\n    parser.add_argument(\n        \"--organic-like-target-weight\",\n        type=float,\n        default=Config.organic_like_target_weight,\n    )\n    parser.add_argument(\n        \"--discovery-horizon-days\",\n        type=int,\n        default=Config.discovery_horizon_days,\n    )\n    parser.add_argument(\n        \"--validation-fraction\",\n        type=float,\n        default=Config.validation_fraction,\n    )\n    parser.add_argument(\n        \"--max-train-targets-per-user\",\n        type=int,\n        default=Config.max_train_targets_per_user,\n        help=\"retain this many recent pre-validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--max-validation-targets-per-user\",\n        type=int,\n        default=Config.max_validation_targets_per_user,\n        help=\"retain this many final validation targets per user; 0 is uncapped\",\n    )\n    parser.add_argument(\n        \"--early-stopping-patience\",\n        type=int,\n        default=Config.early_stopping_patience,\n    )\n    parser.add_argument(\n        \"--early-stopping-min-delta\",\n        type=float,\n        default=Config.early_stopping_min_delta,\n    )\n    parser.add_argument(\"--checkpoint-dir\", type=Path)\n    parser.add_argument(\"--resume-checkpoint\", type=Path)\n    parser.add_argument(\"--seed\", type=int, default=Config.seed)\n    parser.add_argument(\"--ranking-batch-size\", type=int, default=64)\n    parser.add_argument(\"--prepare-only\", action=\"store_true\")\n    args = parser.parse_args()\n\n    if args.threads < 1 or args.bptt_steps < 2 or args.user_batch_size < 1:\n        parser.error(\"threads, BPTT steps, and user batch size must be positive\")\n    if (\n        args.epochs < 1\n        or args.learning_rate <= 0\n        or args.loss_microbatch_size < 1\n        or args.early_stopping_patience < 1\n        or args.early_stopping_min_delta < 0\n        or args.ordinary_target_weight <= 0\n        or args.organic_strong_target_weight <= 0\n        or args.organic_like_target_weight <= 0\n        or args.discovery_horizon_days < 1\n        or args.max_train_targets_per_user < 0\n        or args.max_validation_targets_per_user < 0\n    ):\n        parser.error(\"training counts, learning rate, and patience are invalid\")\n    if not 0.0 < args.validation_fraction < 1.0:\n        parser.error(\"validation fraction must be strictly between zero and one\")\n    public = args.public_dir.resolve()\n    if not (public / \"data\" / \"candidate_catalog.parquet\").is_file():\n        parser.error(f\"public task data not found under {public}\")\n    config = Config(\n        bptt_steps=args.bptt_steps,\n        user_batch_size=args.user_batch_size,\n        epochs=args.epochs,\n        learning_rate=args.learning_rate,\n        loss_microbatch_size=args.loss_microbatch_size,\n        negative_filter_scope=args.negative_filter_scope,\n        target_weighting=args.target_weighting,\n        ordinary_target_weight=args.ordinary_target_weight,\n        organic_strong_target_weight=args.organic_strong_target_weight,\n        organic_like_target_weight=args.organic_like_target_weight,\n        discovery_horizon_days=args.discovery_horizon_days,\n        validation_fraction=args.validation_fraction,\n        max_train_targets_per_user=args.max_train_targets_per_user,\n        max_validation_targets_per_user=args.max_validation_targets_per_user,\n        early_stopping_patience=args.early_stopping_patience,\n        early_stopping_min_delta=args.early_stopping_min_delta,\n        seed=args.seed,\n    )\n    torch.set_num_threads(args.threads)\n    torch.set_num_interop_threads(1)\n    seed_everything(config.seed)\n    device = torch.device(args.device)\n    if device.type == \"mps\" and not torch.backends.mps.is_available():\n        parser.error(\"MPS was requested but is unavailable\")\n\n    started = time.monotonic()\n    prepared, eligibility = load_or_prepare(\n        public,\n        args.stage,\n        config,\n        args.prepared_cache.resolve() if args.prepared_cache else None,\n    )\n    target_partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    if args.prepare_only:\n        print(\n            json.dumps(\n                {\n                    \"stage\": args.stage,\n                    \"sequence_users\": len(prepared.user_ids),\n                    \"sequence_tokens\": len(prepared.sequence_items),\n                    \"next_item_targets\": prepared.target_count,\n                    \"selected_training_targets\": int(\n                        target_partition.training_counts.sum()\n                    ),\n                    \"selected_validation_targets\": int(\n                        target_partition.validation_counts.sum()\n                    ),\n                    \"discarded_old_targets\": int(\n                        target_partition.window_starts.sum()\n                    ),\n                    \"target_users\": len(eligibility.uids),\n                    \"runtime_seconds\": round(time.monotonic() - started, 3),\n                    \"config\": asdict(config),\n                },\n                indent=2,\n            )\n        )\n        return 0\n\n    model, training_history = train_model(\n        public,\n        args.stage,\n        prepared,\n        config,\n        device,\n        args.checkpoint_dir.resolve() if args.checkpoint_dir else None,\n        args.resume_checkpoint.resolve() if args.resume_checkpoint else None,\n    )\n    ranking, embedding_diagnostics = rank_candidates(\n        model,\n        prepared,\n        eligibility,\n        config,\n        device,\n        args.ranking_batch_size,\n    )\n    write_ranking(ranking, args.output.resolve())\n    print(\n        json.dumps(\n            {\n                \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n                \"stage\": args.stage,\n                \"output\": str(args.output.resolve()),\n                \"rows\": len(ranking),\n                \"users\": int(ranking.uid.nunique()),\n                \"runtime_seconds\": round(time.monotonic() - started, 3),\n                \"public_inputs_only\": True,\n                \"architecture\": {\n                    \"family\": \"pure-windowed-sequence-two-tower\",\n                    \"sequence_training\": (\n                        \"every-adjacent-target-within-recent-chronological-window\"\n                    ),\n                    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n                    \"bptt_hidden_state\": \"carried-and-detached\",\n                    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n                    \"loss_execution\": \"gradient-accumulated-microbatches\",\n                    \"user_id_embedding\": False,\n                    \"user_mlp\": \"582-512-256-192\",\n                    \"item_mlp\": \"196-512-256-192\",\n                    \"normalization\": \"none\",\n                    \"score\": \"raw-dot-product\",\n                    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n                    \"negative_sampling\": (\n                        \"24-uniform-plus-8-propensity-corrected-inbatch\"\n                    ),\n                    \"false_negative_filter\": config.negative_filter_scope,\n                    \"target_weighting\": config.target_weighting,\n                },\n                \"config\": asdict(config),\n                \"sequence_tokens\": len(prepared.sequence_items),\n                \"all_next_item_targets\": prepared.target_count,\n                \"selected_training_targets\": int(\n                    target_partition.training_counts.sum()\n                ),\n                \"selected_validation_targets\": int(\n                    target_partition.validation_counts.sum()\n                ),\n                \"discarded_old_targets\": int(target_partition.window_starts.sum()),\n                \"training_history\": training_history,\n                \"embedding_diagnostics\": embedding_diagnostics,\n                \"torch_version\": torch.__version__,\n                \"device\": str(device),\n            },\n            indent=2,\n        )\n    )\n    return 0\n"
            }
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:40:05.680Z",
          "data": {
            "type": "token_usage_record",
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            "turn_token_usage": {
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      ]
    },
    {
      "id": 10,
      "role": "agent",
      "timestamp": "2026-09-23T21:40:09.041Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:40:09.041Z",
          "text": ""
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:40:12.412Z",
          "text": "The baseline’s core limitation is now clear enough to test: 24 of 32 negatives are catalog-uniform, so most are trivially irrelevant tail tracks; the eight in-batch negatives are only mildly harder and are explicitly down/up-weighted toward uniform exposure. That teaches broad separation, but not the top-of-list distinctions NDCG@10 needs. I’m reproducing its public score and caching the prepared sequences so subsequent objective experiments only pay training cost."
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:40:15.392Z",
          "callId": "call_0Csx8XSiFujV9uzOMW2W1xG9",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"python /app/solution/train_current_model.py --stage validation --public-dir /task --output /app/solution/production_validation.parquet --prepared-cache /app/solution/validation_cache.npz --checkpoint-dir /app/solution/baseline_ckpt --threads 8\",workdir:\"/app\",yield_time_ms:1000,max_output_tokens:3000}); text(JSON.stringify(r))\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:40:15.601Z",
            "content": "Script completed\nWall time 0.2 seconds\nOutput:\n\n{\"chunk_id\":\"e9ecf4\",\"wall_time_seconds\":0.040675798,\"exit_code\":1,\"original_token_count\":43,\"output\":\"Traceback (most recent call last):\\n  File \\\"/app/solution/train_current_model.py\\\", line 28, in <module>\\n    import numpy as np\\nModuleNotFoundError: No module named 'numpy'\\n\"}",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:40:15.436Z",
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            }
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:40:15.596Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-2e472eb5-bca5-4a7b-8359-0c72e776bfde",
              "process_id": "38190",
              "command": [
                "/bin/sh",
                "-lc",
                "python /app/solution/train_current_model.py --stage validation --public-dir /task --output /app/solution/production_validation.parquet --prepared-cache /app/solution/validation_cache.npz --checkpoint-dir /app/solution/baseline_ckpt --threads 8"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "python /app/solution/train_current_model.py --stage validation --public-dir /task --output /app/solution/production_validation.parquet --prepared-cache /app/solution/validation_cache.npz --checkpoint-dir /app/solution/baseline_ckpt --threads 8"
                }
              ],
              "source": "unified_exec_startup",
              "status": "failed",
              "stdout": "Traceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 28, in <module>\n    import numpy as np\nModuleNotFoundError: No module named 'numpy'\n",
              "stderr": "",
              "aggregated_output": "Traceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 28, in <module>\n    import numpy as np\nModuleNotFoundError: No module named 'numpy'\n",
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              "duration": {
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                "nanos": 40698469
              },
              "formatted_output": "Traceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 28, in <module>\n    import numpy as np\nModuleNotFoundError: No module named 'numpy'\n"
            }
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        }
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    {
      "id": 11,
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      "timestamp": "2026-09-23T21:40:17.781Z",
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          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"which python; python --version; ls -la /task /task/current_model /app; sed -n '1,160p' /task/requirements.txt; find / -maxdepth 3 -type f -name 'python*' 2>/dev/null | head -30\",workdir:\"/app\",yield_time_ms:10000,max_output_tokens:10000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:40:21.315Z",
            "content": "Script completed\nWall time 0.1 seconds\nOutput:\n\n/usr/local/bin/python\nPython 3.12.13\n/app:\ntotal 16\ndrwxr-xr-x 1 agent agent 4096 Sep 23 21:36 .\ndrwxr-xr-x 1 root  root  4096 Sep 23 21:39 ..\ndrwxr-xr-x 1 agent agent 4096 Sep 23 21:39 solution\n\n/task:\ntotal 40\ndr-xr-xr-x 1 root root 4096 Sep 23 21:36 .\ndrwxr-xr-x 1 root root 4096 Sep 23 21:39 ..\n-r--r--r-- 1 root root    0 Sep 23 21:34 .keep\ndr-xr-xr-x 1 root root 4096 Sep 23 21:34 current_model\ndr-xr-xr-x 1 root root 4096 Sep 23 21:35 data\n-r--r--r-- 1 root root 5774 Sep 23 21:34 evaluate_public.py\n-r--r--r-- 1 root root 8265 Sep 23 21:34 ranking_evaluation.py\n-r--r--r-- 1 root root 1295 Sep 23 21:34 requirements.txt\n\n/task/current_model:\ntotal 104\ndr-xr-xr-x 1 root root  4096 Sep 23 21:34 .\ndr-xr-xr-x 1 root root  4096 Sep 23 21:36 ..\n-r--r--r-- 1 root root 80058 Sep 23 21:34 train_current_model.py\n-r--r--r-- 1 root root 15985 Sep 23 21:34 two_tower_model.py\n# Exact distribution inventory for the Yambda two-tower task family.\n#\n# This is an input to `uv pip sync`, not a list of minimum requirements. A\n# conforming task environment contains exactly these third-party Python\n# distributions and no others. Python itself is pinned by task.toml and both\n# Harbor image Dockerfiles.\nattrs==26.1.0\nbleach==6.4.0\ncertifi==2026.7.22\nchardet==7.6.0\ncharset-normalizer==3.5.1\nfastjsonschema==2.22.2\nfilelock==3.32.3\nfsspec==2026.7.0\nidna==3.18\nJinja2==3.1.6\njoblib==1.5.3\njsonschema==4.26.0\njsonschema-specifications==2025.9.1\njupyter-core==5.9.1\njupytext==1.19.5\nkaggle==2.2.4\nkagglesdk==0.1.37\nmarkdown-it-py==4.2.0\nMarkupSafe==3.0.3\nmdit-py-plugins==0.6.1\nmdurl==0.1.2\nmpmath==1.3.0\nnbformat==5.11.1\nnetworkx==3.6.1\nnumpy==2.2.6\npackaging==26.3\npandas==2.3.3\npillow==12.3.0\npip==26.0.1\nplatformdirs==4.11.3\nprotobuf==7.35.1\npyarrow==18.1.0\npython-dateutil==2.9.0.post0\npython-dotenv==1.2.3\npython-slugify==8.0.4\npytz==2026.3.post1\nPyYAML==6.0.3\nreferencing==0.37.0\nreportlab==4.2.5\nrequests==2.34.2\nrpds-py==2026.6.3\nscikit-learn==1.7.2\nscipy==1.15.3\nsetuptools==84.0.0\nsix==1.17.0\nsympy==1.14.0\ntext-unidecode==1.3\nthreadpoolctl==3.6.0\ntorch==2.8.0\ntqdm==4.70.0\ntraitlets==5.16.1\ntyping-extensions==4.16.0\ntzdata==2026.3\nurllib3==2.7.0\nwebencodings==0.6.1\n",
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              "process_id": "66754",
              "command": [
                "/bin/sh",
                "-lc",
                "which python; python --version; ls -la /task /task/current_model /app; sed -n '1,160p' /task/requirements.txt; find / -maxdepth 3 -type f -name 'python*' 2>/dev/null | head -30"
              ],
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                  "type": "unknown",
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              "stdout": "/usr/local/bin/python\nPython 3.12.13\n/app:\ntotal 16\ndrwxr-xr-x 1 agent agent 4096 Sep 23 21:36 .\ndrwxr-xr-x 1 root  root  4096 Sep 23 21:39 ..\ndrwxr-xr-x 1 agent agent 4096 Sep 23 21:39 solution\n\n/task:\ntotal 40\ndr-xr-xr-x 1 root root 4096 Sep 23 21:36 .\ndrwxr-xr-x 1 root root 4096 Sep 23 21:39 ..\n-r--r--r-- 1 root root    0 Sep 23 21:34 .keep\ndr-xr-xr-x 1 root root 4096 Sep 23 21:34 current_model\ndr-xr-xr-x 1 root root 4096 Sep 23 21:35 data\n-r--r--r-- 1 root root 5774 Sep 23 21:34 evaluate_public.py\n-r--r--r-- 1 root root 8265 Sep 23 21:34 ranking_evaluation.py\n-r--r--r-- 1 root root 1295 Sep 23 21:34 requirements.txt\n\n/task/current_model:\ntotal 104\ndr-xr-xr-x 1 root root  4096 Sep 23 21:34 .\ndr-xr-xr-x 1 root root  4096 Sep 23 21:36 ..\n-r--r--r-- 1 root root 80058 Sep 23 21:34 train_current_model.py\n-r--r--r-- 1 root root 15985 Sep 23 21:34 two_tower_model.py\n# Exact distribution inventory for the Yambda two-tower task family.\n#\n# This is an input to `uv pip sync`, not a list of minimum requirements. A\n# conforming task environment contains exactly these third-party Python\n# distributions and no others. Python itself is pinned by task.toml and both\n# Harbor image Dockerfiles.\nattrs==26.1.0\nbleach==6.4.0\ncertifi==2026.7.22\nchardet==7.6.0\ncharset-normalizer==3.5.1\nfastjsonschema==2.22.2\nfilelock==3.32.3\nfsspec==2026.7.0\nidna==3.18\nJinja2==3.1.6\njoblib==1.5.3\njsonschema==4.26.0\njsonschema-specifications==2025.9.1\njupyter-core==5.9.1\njupytext==1.19.5\nkaggle==2.2.4\nkagglesdk==0.1.37\nmarkdown-it-py==4.2.0\nMarkupSafe==3.0.3\nmdit-py-plugins==0.6.1\nmdurl==0.1.2\nmpmath==1.3.0\nnbformat==5.11.1\nnetworkx==3.6.1\nnumpy==2.2.6\npackaging==26.3\npandas==2.3.3\npillow==12.3.0\npip==26.0.1\nplatformdirs==4.11.3\nprotobuf==7.35.1\npyarrow==18.1.0\npython-dateutil==2.9.0.post0\npython-dotenv==1.2.3\npython-slugify==8.0.4\npytz==2026.3.post1\nPyYAML==6.0.3\nreferencing==0.37.0\nreportlab==4.2.5\nrequests==2.34.2\nrpds-py==2026.6.3\nscikit-learn==1.7.2\nscipy==1.15.3\nsetuptools==84.0.0\nsix==1.17.0\nsympy==1.14.0\ntext-unidecode==1.3\nthreadpoolctl==3.6.0\ntorch==2.8.0\ntqdm==4.70.0\ntraitlets==5.16.1\ntyping-extensions==4.16.0\ntzdata==2026.3\nurllib3==2.7.0\nwebencodings==0.6.1\n",
              "stderr": "",
              "aggregated_output": "/usr/local/bin/python\nPython 3.12.13\n/app:\ntotal 16\ndrwxr-xr-x 1 agent agent 4096 Sep 23 21:36 .\ndrwxr-xr-x 1 root  root  4096 Sep 23 21:39 ..\ndrwxr-xr-x 1 agent agent 4096 Sep 23 21:39 solution\n\n/task:\ntotal 40\ndr-xr-xr-x 1 root root 4096 Sep 23 21:36 .\ndrwxr-xr-x 1 root root 4096 Sep 23 21:39 ..\n-r--r--r-- 1 root root    0 Sep 23 21:34 .keep\ndr-xr-xr-x 1 root root 4096 Sep 23 21:34 current_model\ndr-xr-xr-x 1 root root 4096 Sep 23 21:35 data\n-r--r--r-- 1 root root 5774 Sep 23 21:34 evaluate_public.py\n-r--r--r-- 1 root root 8265 Sep 23 21:34 ranking_evaluation.py\n-r--r--r-- 1 root root 1295 Sep 23 21:34 requirements.txt\n\n/task/current_model:\ntotal 104\ndr-xr-xr-x 1 root root  4096 Sep 23 21:34 .\ndr-xr-xr-x 1 root root  4096 Sep 23 21:36 ..\n-r--r--r-- 1 root root 80058 Sep 23 21:34 train_current_model.py\n-r--r--r-- 1 root root 15985 Sep 23 21:34 two_tower_model.py\n# Exact distribution inventory for the Yambda two-tower task family.\n#\n# This is an input to `uv pip sync`, not a list of minimum requirements. A\n# conforming task environment contains exactly these third-party Python\n# distributions and no others. Python itself is pinned by task.toml and both\n# Harbor image Dockerfiles.\nattrs==26.1.0\nbleach==6.4.0\ncertifi==2026.7.22\nchardet==7.6.0\ncharset-normalizer==3.5.1\nfastjsonschema==2.22.2\nfilelock==3.32.3\nfsspec==2026.7.0\nidna==3.18\nJinja2==3.1.6\njoblib==1.5.3\njsonschema==4.26.0\njsonschema-specifications==2025.9.1\njupyter-core==5.9.1\njupytext==1.19.5\nkaggle==2.2.4\nkagglesdk==0.1.37\nmarkdown-it-py==4.2.0\nMarkupSafe==3.0.3\nmdit-py-plugins==0.6.1\nmdurl==0.1.2\nmpmath==1.3.0\nnbformat==5.11.1\nnetworkx==3.6.1\nnumpy==2.2.6\npackaging==26.3\npandas==2.3.3\npillow==12.3.0\npip==26.0.1\nplatformdirs==4.11.3\nprotobuf==7.35.1\npyarrow==18.1.0\npython-dateutil==2.9.0.post0\npython-dotenv==1.2.3\npython-slugify==8.0.4\npytz==2026.3.post1\nPyYAML==6.0.3\nreferencing==0.37.0\nreportlab==4.2.5\nrequests==2.34.2\nrpds-py==2026.6.3\nscikit-learn==1.7.2\nscipy==1.15.3\nsetuptools==84.0.0\nsix==1.17.0\nsympy==1.14.0\ntext-unidecode==1.3\nthreadpoolctl==3.6.0\ntorch==2.8.0\ntqdm==4.70.0\ntraitlets==5.16.1\ntyping-extensions==4.16.0\ntzdata==2026.3\nurllib3==2.7.0\nwebencodings==0.6.1\n",
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                "nanos": 3790
              },
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            "content": "Script completed\nWall time 3.9 seconds\nOutput:\n\ntotal 124\ndr-xr-xr-x 1 root root 4096 Sep 23 21:36 .\ndr-xr-xr-x 1 root root 4096 Sep 23 21:36 ..\n-r--r--r-- 1 root root 9033 Sep 23 21:36 Activate.ps1\n-r--r--r-- 1 root root 2158 Sep 23 21:36 activate\n-r--r--r-- 1 root root  920 Sep 23 21:36 activate.csh\n-r--r--r-- 1 root root 2195 Sep 23 21:36 activate.fish\n-r-xr-xr-x 1 root root  302 Sep 23 21:36 chardetect\n-r-xr-xr-x 1 root root  304 Sep 23 21:36 dotenv\n-r-xr-xr-x 1 root root  308 Sep 23 21:36 f2py\n-r-xr-xr-x 1 root root  299 Sep 23 21:36 idna\n-r-xr-xr-x 1 root root  297 Sep 23 21:36 isympy\n-r-xr-xr-x 1 root root  305 Sep 23 21:36 jsonschema\n-r-xr-xr-x 1 root root  311 Sep 23 21:36 jupyter\n-r-xr-xr-x 1 root root  311 Sep 23 21:36 jupyter-migrate\n-r-xr-xr-x 1 root root  316 Sep 23 21:36 jupyter-troubleshoot\n-r-xr-xr-x 1 root root  344 Sep 23 21:36 jupyter-trust\n-r-xr-xr-x 1 root root  311 Sep 23 21:36 jupytext\n-r-xr-xr-x 1 root root  315 Sep 23 21:36 jupytext-config\n-r-xr-xr-x 1 root root  301 Sep 23 21:36 kaggle\n-r-xr-xr-x 1 root root  312 Sep 23 21:36 markdown-it\n-r-xr-xr-x 1 root root  325 Sep 23 21:36 normalizer\n-r-xr-xr-x 1 root root  308 Sep 23 21:36 numpy-config\n-r-xr-xr-x 1 root root  313 Sep 23 21:36 pip\n-r-xr-xr-x 1 root root  313 Sep 23 21:36 pip3\n-r-xr-xr-x 1 root root  313 Sep 23 21:36 pip3.12\nlrwxrwxrwx 1 root root   21 Sep 23 21:36 python -> /usr/local/bin/python\nlrwxrwxrwx 1 root root    6 Sep 23 21:36 python3 -> python\nlrwxrwxrwx 1 root root    6 Sep 23 21:36 python3.12 -> python\n-r-xr-xr-x 1 root root  307 Sep 23 21:36 slugify\nPython 3.12.13\n2.2.6 2.8.0+cpu\n",
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          "result": {
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            "content": "Script completed\nWall time 1.2 seconds\nOutput:\n\n{\"chunk_id\":\"aea014\",\"wall_time_seconds\":1.001252084,\"session_id\":86745,\"original_token_count\":0,\"output\":\"\"}",
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            "content": "Script completed\nWall time 30.0 seconds\nOutput:\n\nprepared users=6,000 tokens=13,061,727 states=217,148 elapsed=30.1s\nprepared users=7,000 tokens=15,334,418 states=256,914 elapsed=35.6s\nprepared users=8,000 tokens=17,462,672 states=296,703 elapsed=40.9s\nprepared users=9,000 tokens=19,568,405 states=331,551 elapsed=45.6s\ntarget users without qualifying catalog sequence=7\nprepared stage=validation sequence_users=9,135 tokens=20,056,329 next_item_targets=20,047,194 states=339,133\nsaved public-derived full-sequence cache: /app/solution/validation_cache.npz\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\n",
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          "text": "Sequence preparation found about 20.0M historical positive-listen tokens, while the baseline trains on only the most recent 1.05M adjacent targets. The experiment setup is now cached. I’m letting the baseline finish, then I’ll compare candidate-aware hard negatives against the exact same data window and seed; this isolates the negative-selection change rather than conflating it with architecture or data leakage."
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            "content": "Script completed\nWall time 12.8 seconds\nOutput:\n\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/production_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 361.155,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_loss\": 0.496636218959915,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.791078352\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.603016972541809,\n    \"query_norm_std\": 0.7697497606277466,\n    \"item_norm_mean\": 1.7570279836654663,\n    \"item_norm_std\": 0.8279485702514648\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
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              "status": "completed",
              "stdout": "loaded explicit events: rows=720,270 users=8,220\nprepared users=1,000 tokens=2,090,746 states=35,727 elapsed=4.9s\nprepared users=2,000 tokens=4,301,266 states=71,242 elapsed=9.9s\nprepared users=3,000 tokens=6,486,146 states=109,471 elapsed=15.1s\nprepared users=4,000 tokens=8,793,043 states=148,210 elapsed=20.5s\nprepared users=5,000 tokens=10,992,205 states=182,596 elapsed=25.4s\nprepared users=6,000 tokens=13,061,727 states=217,148 elapsed=30.1s\nprepared users=7,000 tokens=15,334,418 states=256,914 elapsed=35.6s\nprepared users=8,000 tokens=17,462,672 states=296,703 elapsed=40.9s\nprepared users=9,000 tokens=19,568,405 states=331,551 elapsed=45.6s\ntarget users without qualifying catalog sequence=7\nprepared stage=validation sequence_users=9,135 tokens=20,056,329 next_item_targets=20,047,194 states=339,133\nsaved public-derived full-sequence cache: /app/solution/validation_cache.npz\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nepoch=1/1 batches=250 targets=987,417 batch_bce=0.547529 running_bce=0.541614 elapsed=197.9s\nsaved epoch checkpoint: /app/solution/baseline_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.53984 validation_loss=0.49664 pair_accuracy=0.755 train_targets=1,052,953 validation_targets=130,103 train_seconds=211.0 validation_seconds=15.8\nrestored best validation-BCE checkpoint: epoch=1 loss=0.496636\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/production_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 361.155,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_loss\": 0.496636218959915,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.791078352\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.603016972541809,\n    \"query_norm_std\": 0.7697497606277466,\n    \"item_norm_mean\": 1.7570279836654663,\n    \"item_norm_std\": 0.8279485702514648\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "stderr": "",
              "aggregated_output": "loaded explicit events: rows=720,270 users=8,220\nprepared users=1,000 tokens=2,090,746 states=35,727 elapsed=4.9s\nprepared users=2,000 tokens=4,301,266 states=71,242 elapsed=9.9s\nprepared users=3,000 tokens=6,486,146 states=109,471 elapsed=15.1s\nprepared users=4,000 tokens=8,793,043 states=148,210 elapsed=20.5s\nprepared users=5,000 tokens=10,992,205 states=182,596 elapsed=25.4s\nprepared users=6,000 tokens=13,061,727 states=217,148 elapsed=30.1s\nprepared users=7,000 tokens=15,334,418 states=256,914 elapsed=35.6s\nprepared users=8,000 tokens=17,462,672 states=296,703 elapsed=40.9s\nprepared users=9,000 tokens=19,568,405 states=331,551 elapsed=45.6s\ntarget users without qualifying catalog sequence=7\nprepared stage=validation sequence_users=9,135 tokens=20,056,329 next_item_targets=20,047,194 states=339,133\nsaved public-derived full-sequence cache: /app/solution/validation_cache.npz\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nepoch=1/1 batches=250 targets=987,417 batch_bce=0.547529 running_bce=0.541614 elapsed=197.9s\nsaved epoch checkpoint: /app/solution/baseline_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.53984 validation_loss=0.49664 pair_accuracy=0.755 train_targets=1,052,953 validation_targets=130,103 train_seconds=211.0 validation_seconds=15.8\nrestored best validation-BCE checkpoint: epoch=1 loss=0.496636\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/production_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 361.155,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_loss\": 0.496636218959915,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.791078352\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.603016972541809,\n    \"query_norm_std\": 0.7697497606277466,\n    \"item_norm_mean\": 1.7570279836654663,\n    \"item_norm_std\": 0.8279485702514648\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "exit_code": 0,
              "duration": {
                "secs": 365,
                "nanos": 385897560
              },
              "formatted_output": "loaded explicit events: rows=720,270 users=8,220\nprepared users=1,000 tokens=2,090,746 states=35,727 elapsed=4.9s\nprepared users=2,000 tokens=4,301,266 states=71,242 elapsed=9.9s\nprepared users=3,000 tokens=6,486,146 states=109,471 elapsed=15.1s\nprepared users=4,000 tokens=8,793,043 states=148,210 elapsed=20.5s\nprepared users=5,000 tokens=10,992,205 states=182,596 elapsed=25.4s\nprepared users=6,000 tokens=13,061,727 states=217,148 elapsed=30.1s\nprepared users=7,000 tokens=15,334,418 states=256,914 elapsed=35.6s\nprepared users=8,000 tokens=17,462,672 states=296,703 elapsed=40.9s\nprepared users=9,000 tokens=19,568,405 states=331,551 elapsed=45.6s\ntarget users without qualifying catalog sequence=7\nprepared stage=validation sequence_users=9,135 tokens=20,056,329 next_item_targets=20,047,194 states=339,133\nsaved public-derived full-sequence cache: /app/solution/validation_cache.npz\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nepoch=1/1 batches=250 targets=987,417 batch_bce=0.547529 running_bce=0.541614 elapsed=197.9s\nsaved epoch checkpoint: /app/solution/baseline_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.53984 validation_loss=0.49664 pair_accuracy=0.755 train_targets=1,052,953 validation_targets=130,103 train_seconds=211.0 validation_seconds=15.8\nrestored best validation-BCE checkpoint: epoch=1 loss=0.496636\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/production_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 361.155,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_loss\": 0.496636218959915,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.791078352\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.603016972541809,\n    \"query_norm_std\": 0.7697497606277466,\n    \"item_norm_mean\": 1.7570279836654663,\n    \"item_norm_std\": 0.8279485702514648\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n"
            }
          }
        }
      ]
    },
    {
      "id": 26,
      "role": "agent",
      "timestamp": "2026-09-23T21:46:50.657Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:46:50.657Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:46:52.559Z",
          "callId": "call_YbJRxfyOUNQET8MjIMFP2A3P",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python /task/evaluate_public.py /app/solution/production_validation.parquet\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:5000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:46:55.927Z",
            "content": "Script completed\nWall time 3.4 seconds\nOutput:\n\n{\n  \"model\": \"/app/solution/production_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.02128,\n    \"quality_users\": 4263\n  }\n}\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:46:52.623Z",
          "data": {
            "type": "token_usage_record",
            "thread_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "session_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "response_id": "resp_038c43f9aa686cae016ab448c91d9c87d2866468c612c0dd60",
            "usage": {
              "input_tokens": 43558,
              "cached_input_tokens": 42240,
              "cache_write_input_tokens": 0,
              "output_tokens": 75,
              "reasoning_output_tokens": 6,
              "total_tokens": 43633
            },
            "turn_token_usage": {
              "input_tokens": 804367,
              "cached_input_tokens": 768512,
              "cache_write_input_tokens": 0,
              "output_tokens": 2158,
              "reasoning_output_tokens": 336,
              "total_tokens": 806525
            },
            "thread_token_usage": {
              "input_tokens": 804367,
              "cached_input_tokens": 768512,
              "cache_write_input_tokens": 0,
              "output_tokens": 2158,
              "reasoning_output_tokens": 336,
              "total_tokens": 806525
            }
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:46:55.923Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-5b956434-3676-4c2c-963b-8a95701bed68",
              "process_id": "26667",
              "command": [
                "/bin/sh",
                "-lc",
                "/opt/task-venv/bin/python /task/evaluate_public.py /app/solution/production_validation.parquet"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python /task/evaluate_public.py /app/solution/production_validation.parquet"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "{\n  \"model\": \"/app/solution/production_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.02128,\n    \"quality_users\": 4263\n  }\n}\n",
              "stderr": "",
              "aggregated_output": "{\n  \"model\": \"/app/solution/production_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.02128,\n    \"quality_users\": 4263\n  }\n}\n",
              "exit_code": 0,
              "duration": {
                "secs": 3,
                "nanos": 196533162
              },
              "formatted_output": "{\n  \"model\": \"/app/solution/production_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.02128,\n    \"quality_users\": 4263\n  }\n}\n"
            }
          }
        }
      ]
    },
    {
      "id": 27,
      "role": "agent",
      "timestamp": "2026-09-23T21:47:11.750Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:47:11.750Z",
          "text": ""
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:47:14.826Z",
          "text": "Baseline reproduced at NDCG@10 = 0.02128. Its loss looks healthy (0.4966 validation BCE), but that metric is dominated by easy sampled negatives and is poorly aligned with top-10 retrieval. Before committing compute time, I’m checking where public positives sit in catalog popularity and whether the current ranking’s misses are concentrated among plausible head candidates; that will set the hard-negative proposal distribution."
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:47:26.853Z",
          "callId": "call_h6Lxpit2HSprHrluPn0iSULa",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"sed -n '1,260p' /task/evaluate_public.py; /opt/task-venv/bin/python - <<'PY'\\nimport pandas as pd, numpy as np\\nD='/task/data'\\ncat=pd.read_parquet(D+'/candidate_catalog.parquet').sort_values('popularity_rank').reset_index(drop=True)\\nidx=pd.Series(np.arange(len(cat)),index=cat.item_id)\\nls=pd.read_parquet(D+'/val_listens.parquet',columns=['uid','item_id','is_organic','played_ratio_pct'])\\nli=pd.read_parquet(D+'/val_likes.parquet',columns=['uid','item_id','is_organic'])\\ntarget=set(pd.read_parquet(D+'/target_users.parquet').uid)\\nls=ls[ls.uid.isin(target)&(ls.is_organic==1)&(ls.played_ratio_pct>=80)&ls.item_id.isin(idx.index)]\\nli=li[li.uid.isin(target)&(li.is_organic==1)&li.item_id.isin(idx.index)]\\nfor name,x in [('listen80',ls),('likes',li)]:\\n r=idx.loc[x.item_id].to_numpy()+1\\n print(name,len(x),'users',x.uid.nunique(),'rank quantiles',np.quantile(r,[0,.1,.25,.5,.75,.9,.99,1]).astype(int))\\n for k in [100,500,1000,3000,5000,10000,20000,30000]: print(k,(r<=k).mean(),end='; ')\\n print()\\nPY\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:12000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:47:28.595Z",
            "content": "Script completed\nWall time 1.7 seconds\nOutput:\n\n#!/usr/bin/env python3\n\"\"\"Score a validation-stage ranking against public discovery labels.\n\n``build_task.py`` publishes this module with the solver-visible task files. It\nloads target users, validation eligibility, and validation-window events from\nthe adjacent ``data`` directory, then evaluates one ranking supplied on the\ncommand line. Stage-independent mechanics come from the adjacent public\n``ranking_evaluation.py`` module. The builder installs the same checked-in\nmodule in the private judge, so public and private scoring mechanics cannot\ndrift. A relevant candidate receives grade 3 for an organic like or grade 1 for\nan organic listen with at least 80 percent completion; a like takes precedence\nwhen both events exist.\n\nBefore scoring, the ranking must contain exactly 100 distinct eligible items\nfor every target user, with integer-valued ``uid``, ``item_id``, and ``rank``\ncolumns and ranks 1 through 100 exactly once per user. Extra columns are\nignored. Quality is graded NDCG@10, averaged only over users who have at least\none eligible relevant item in the validation window.\n\nThe evaluator prints a JSON object containing the model path and scores. It\ndoes not apply the task's pass threshold; its purpose is model development and\nselection. The private judge applies the threshold to the final submission.\n\nUsage::\n\n    python evaluate_public.py <validation-ranking.parquet|csv>\n\"\"\"\nfrom __future__ import annotations\n\nimport json\nimport sys\nfrom pathlib import Path\n\nimport pandas as pd\n\nfrom ranking_evaluation import (\n    CandidateSet,\n    RankingValidationError,\n    ranked_items,\n    read_ranking,\n    score_rankings,\n    validate_ranking,\n)\n\n\nHERE = Path(__file__).resolve().parent\nDATA = HERE / \"data\"\nLISTEN_STRONG = 80\n\n\ndef validation_truth(\n    eligibility: CandidateSet, targets: set[int]\n) -> dict[int, dict[int, int]]:\n    \"\"\"Build cutoff-correct graded relevance from public validation events.\n\n    Only target-user events for eligible candidates are retained. Organic\n    listens completed to at least 80 percent receive grade 1, and organic likes\n    receive grade 3. Repeated user-item events are collapsed, and processing\n    likes second ensures that grade 3 wins over grade 1.\n\n    Args:\n        eligibility: Validation-cutoff candidate membership service.\n        targets: Complete set of target user IDs.\n\n    Returns:\n        A nested ``uid -> item_id -> grade`` mapping. Users without an eligible\n        relevant event are omitted.\n    \"\"\"\n    listens = pd.read_parquet(DATA / \"val_listens.parquet\")\n    likes = pd.read_parquet(DATA / \"val_likes.parquet\")\n    strong = listens[\n        listens.uid.isin(targets)\n        & (listens.is_organic == 1)\n        & (listens.played_ratio_pct >= LISTEN_STRONG)\n    ][[\"uid\", \"item_id\"]].drop_duplicates()\n    organic_likes = likes[\n        likes.uid.isin(targets) & (likes.is_organic == 1)\n    ][[\"uid\", \"item_id\"]].drop_duplicates()\n\n    graded: dict[int, dict[int, int]] = {}\n    for raw_uid, raw_item in strong.itertuples(index=False, name=None):\n        uid, item = int(raw_uid), int(raw_item)\n        if eligibility.is_eligible(uid, item):\n            graded.setdefault(uid, {})[item] = 1\n    for raw_uid, raw_item in organic_likes.itertuples(index=False, name=None):\n        uid, item = int(raw_uid), int(raw_item)\n        if eligibility.is_eligible(uid, item):\n            graded.setdefault(uid, {})[item] = 3\n    return graded\n\n\ndef load_submission(\n    path: Path, eligibility: CandidateSet, targets: set[int]\n) -> dict[int, list[int]]:\n    \"\"\"Load and validate a public validation ranking.\n\n    Files ending in ``.parquet`` are read as parquet; every other suffix is\n    read as CSV. The required columns must be integer-valued, cover exactly the\n    target-user set, contain 100 rows and ranks 1 through 100 per user, avoid\n    duplicate user-item pairs, and contain only cutoff-eligible items.\n\n    Args:\n        path: Ranking file to read.\n        eligibility: Validation-cutoff candidate membership service.\n        targets: Exact set of users the ranking must cover.\n\n    Returns:\n        A ``uid -> ranked item IDs`` mapping ordered by ascending rank.\n\n    Raises:\n        ValueError: If the ranking violates the required schema or invariants.\n    \"\"\"\n    frame = validate_ranking(read_ranking(path), targets)\n    if not all(\n        eligibility.is_eligible(uid, item)\n        for uid, item in frame[[\"uid\", \"item_id\"]].itertuples(index=False, name=None)\n    ):\n        raise RankingValidationError(\n            \"submission contains an item rejected by eligibility service\"\n        )\n    return ranked_items(frame)\n\n\ndef score(\n    ranked: dict[int, list[int]],\n    graded: dict[int, dict[int, int]],\n) -> dict[str, float | int]:\n    \"\"\"Aggregate per-user NDCG@10 over users with public relevance labels.\n\n    Args:\n        ranked: Ranked item IDs for every target user.\n        graded: Eligible validation relevance keyed by user and item.\n\n    Returns:\n        The six-decimal ``quality_ndcg@10`` value and number of scored users.\n    \"\"\"\n    return score_rankings(ranked, graded)\n\n\ndef main() -> None:\n    \"\"\"Run the public evaluator CLI and print its JSON score report.\"\"\"\n    targets_frame = pd.read_parquet(DATA / \"target_users.parquet\")\n    targets = set(targets_frame.uid.astype(int))\n    eligibility = CandidateSet(DATA / \"validation_eligible_candidates.npz\")\n    graded = validation_truth(eligibility, targets)\n\n    if len(sys.argv) != 2:\n        raise SystemExit(\n            \"usage: evaluate_public.py <validation-ranking.parquet|csv>\"\n        )\n    path = Path(sys.argv[1])\n    ranked = load_submission(path, eligibility, targets)\n    print(json.dumps({\"model\": str(path), \"scores\": score(ranked, graded)}, indent=2))\n\n\nif __name__ == \"__main__\":\n    main()\nlisten80 288828 users 6027 rank quantiles [    1   220  1059  4263 11431 20044 28754 30000]\n100 0.061122882822995; 500 0.16506017422133587; 1000 0.24274308585040233; 3000 0.4245121664104588; 5000 0.5382511390862382; 10000 0.7153461575747504; 20000 0.8995284390710042; 30000 1.0; \nlikes 10406 users 2073 rank quantiles [    1   442  1584  5377 13568 21838 28745 29989]\n100 0.029021718239477225; 500 0.11262733038631559; 1000 0.1849894291754757; 3000 0.3694022679223525; 5000 0.48154910628483566; 10000 0.6646165673649818; 20000 0.8711320392081492; 30000 1.0; \n",
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          "timestamp": "2026-09-23T21:47:26.933Z",
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        {
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          "timestamp": "2026-09-23T21:47:28.590Z",
          "data": {
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              "type": "CommandExecution",
              "id": "exec-edd15b48-7007-436f-ac69-7659844aa990",
              "process_id": "77982",
              "command": [
                "/bin/sh",
                "-lc",
                "sed -n '1,260p' /task/evaluate_public.py; /opt/task-venv/bin/python - <<'PY'\nimport pandas as pd, numpy as np\nD='/task/data'\ncat=pd.read_parquet(D+'/candidate_catalog.parquet').sort_values('popularity_rank').reset_index(drop=True)\nidx=pd.Series(np.arange(len(cat)),index=cat.item_id)\nls=pd.read_parquet(D+'/val_listens.parquet',columns=['uid','item_id','is_organic','played_ratio_pct'])\nli=pd.read_parquet(D+'/val_likes.parquet',columns=['uid','item_id','is_organic'])\ntarget=set(pd.read_parquet(D+'/target_users.parquet').uid)\nls=ls[ls.uid.isin(target)&(ls.is_organic==1)&(ls.played_ratio_pct>=80)&ls.item_id.isin(idx.index)]\nli=li[li.uid.isin(target)&(li.is_organic==1)&li.item_id.isin(idx.index)]\nfor name,x in [('listen80',ls),('likes',li)]:\n r=idx.loc[x.item_id].to_numpy()+1\n print(name,len(x),'users',x.uid.nunique(),'rank quantiles',np.quantile(r,[0,.1,.25,.5,.75,.9,.99,1]).astype(int))\n for k in [100,500,1000,3000,5000,10000,20000,30000]: print(k,(r<=k).mean(),end='; ')\n print()\nPY"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "sed -n '1,260p' /task/evaluate_public.py; /opt/task-venv/bin/python - <<'PY'\nimport pandas as pd, numpy as np\nD='/task/data'\ncat=pd.read_parquet(D+'/candidate_catalog.parquet').sort_values('popularity_rank').reset_index(drop=True)\nidx=pd.Series(np.arange(len(cat)),index=cat.item_id)\nls=pd.read_parquet(D+'/val_listens.parquet',columns=['uid','item_id','is_organic','played_ratio_pct'])\nli=pd.read_parquet(D+'/val_likes.parquet',columns=['uid','item_id','is_organic'])\ntarget=set(pd.read_parquet(D+'/target_users.parquet').uid)\nls=ls[ls.uid.isin(target)&(ls.is_organic==1)&(ls.played_ratio_pct>=80)&ls.item_id.isin(idx.index)]\nli=li[li.uid.isin(target)&(li.is_organic==1)&li.item_id.isin(idx.index)]\nfor name,x in [('listen80',ls),('likes',li)]:\n r=idx.loc[x.item_id].to_numpy()+1\n print(name,len(x),'users',x.uid.nunique(),'rank quantiles',np.quantile(r,[0,.1,.25,.5,.75,.9,.99,1]).astype(int))\n for k in [100,500,1000,3000,5000,10000,20000,30000]: print(k,(r<=k).mean(),end='; ')\n print()\nPY"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "listen80 288828 users 6027 rank quantiles [    1   220  1059  4263 11431 20044 28754 30000]\n100 0.061122882822995; 500 0.16506017422133587; 1000 0.24274308585040233; 3000 0.4245121664104588; 5000 0.5382511390862382; 10000 0.7153461575747504; 20000 0.8995284390710042; 30000 1.0; \nlikes 10406 users 2073 rank quantiles [    1   442  1584  5377 13568 21838 28745 29989]\n100 0.029021718239477225; 500 0.11262733038631559; 1000 0.1849894291754757; 3000 0.3694022679223525; 5000 0.48154910628483566; 10000 0.6646165673649818; 20000 0.8711320392081492; 30000 1.0; \n",
              "stderr": "",
              "aggregated_output": "listen80 288828 users 6027 rank quantiles [    1   220  1059  4263 11431 20044 28754 30000]\n100 0.061122882822995; 500 0.16506017422133587; 1000 0.24274308585040233; 3000 0.4245121664104588; 5000 0.5382511390862382; 10000 0.7153461575747504; 20000 0.8995284390710042; 30000 1.0; \nlikes 10406 users 2073 rank quantiles [    1   442  1584  5377 13568 21838 28745 29989]\n100 0.029021718239477225; 500 0.11262733038631559; 1000 0.1849894291754757; 3000 0.3694022679223525; 5000 0.48154910628483566; 10000 0.6646165673649818; 20000 0.8711320392081492; 30000 1.0; \n",
              "exit_code": 0,
              "duration": {
                "secs": 1,
                "nanos": 573625773
              },
              "formatted_output": "listen80 288828 users 6027 rank quantiles [    1   220  1059  4263 11431 20044 28754 30000]\n100 0.061122882822995; 500 0.16506017422133587; 1000 0.24274308585040233; 3000 0.4245121664104588; 5000 0.5382511390862382; 10000 0.7153461575747504; 20000 0.8995284390710042; 30000 1.0; \nlikes 10406 users 2073 rank quantiles [    1   442  1584  5377 13568 21838 28745 29989]\n100 0.029021718239477225; 500 0.11262733038631559; 1000 0.1849894291754757; 3000 0.3694022679223525; 5000 0.48154910628483566; 10000 0.6646165673649818; 20000 0.8711320392081492; 30000 1.0; \n"
            }
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    {
      "id": 28,
      "role": "agent",
      "timestamp": "2026-09-23T21:47:34.281Z",
      "blocks": [
        {
          "kind": "reasoning",
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          "timestamp": "2026-09-23T21:47:34.281Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:47:46.699Z",
          "callId": "call_Kqf2Cnb4B7ekkxL529S0Gc6z",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python - <<'PY'\\nimport pandas as pd, numpy as np, subprocess, json\\nD='/task/data'; O='/app/solution'\\nc=pd.read_parquet(D+'/candidate_catalog.parquet').sort_values('popularity_rank').reset_index(drop=True)\\nprint(c.columns, c.head())\\nz=np.load(D+'/validation_eligible_candidates.npz'); u=z['uids']; items=z['item_ids']; p=z['packed_eligible']; assert np.array_equal(items,c.item_id)\\nmetrics={'poprank':-c.popularity_rank.to_numpy(), 'positive':c.positive_listens.to_numpy(), 'organic':c.organic_positive_listens.to_numpy(), 'org_ratio':c.organic_positive_listens.to_numpy()/np.maximum(c.positive_listens.to_numpy(),1)}\\nfor name,score in metrics.items():\\n rows=[]\\n order=np.argsort(-score,kind='stable')\\n for ri,uid in enumerate(u):\\n  ok=np.unpackbits(p[ri],count=len(items),bitorder='little').astype(bool)\\n  sel=order[ok[order]][:100]\\n  rows.extend((int(uid),int(items[j]),k+1) for k,j in enumerate(sel))\\n out=f'{O}/{name}_validation.parquet'; pd.DataFrame(rows,columns=['uid','item_id','rank']).to_parquet(out,index=False)\\n print(name,out)\\nPY\\nfor f in /app/solution/*_validation.parquet; do /opt/task-venv/bin/python /task/evaluate_public.py \\\"$f\\\" | tr '\\\\n' ' '; echo; done\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:10000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:48:10.229Z",
            "content": "Script completed\nWall time 23.5 seconds\nOutput:\n\nIndex(['item_id', 'positive_listens', 'organic_positive_listens',\n       'popularity_rank'],\n      dtype='object')    item_id  positive_listens  organic_positive_listens  popularity_rank\n0  5862961             26615                     20620                1\n1  6901374             25536                     17347                2\n2  5635052             24691                     17194                3\n3  3542184             24075                     17699                4\n4  9378983             24036                     18195                5\npoprank /app/solution/poprank_validation.parquet\npositive /app/solution/positive_validation.parquet\norganic /app/solution/organic_validation.parquet\norg_ratio /app/solution/org_ratio_validation.parquet\n{   \"model\": \"/app/solution/org_ratio_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.000347,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/organic_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 3.2e-05,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/poprank_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/positive_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/production_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.02128,     \"quality_users\": 4263   } } \n",
            "isError": null
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          "timestamp": "2026-09-23T21:48:10.207Z",
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              "process_id": "52735",
              "command": [
                "/bin/sh",
                "-lc",
                "/opt/task-venv/bin/python - <<'PY'\nimport pandas as pd, numpy as np, subprocess, json\nD='/task/data'; O='/app/solution'\nc=pd.read_parquet(D+'/candidate_catalog.parquet').sort_values('popularity_rank').reset_index(drop=True)\nprint(c.columns, c.head())\nz=np.load(D+'/validation_eligible_candidates.npz'); u=z['uids']; items=z['item_ids']; p=z['packed_eligible']; assert np.array_equal(items,c.item_id)\nmetrics={'poprank':-c.popularity_rank.to_numpy(), 'positive':c.positive_listens.to_numpy(), 'organic':c.organic_positive_listens.to_numpy(), 'org_ratio':c.organic_positive_listens.to_numpy()/np.maximum(c.positive_listens.to_numpy(),1)}\nfor name,score in metrics.items():\n rows=[]\n order=np.argsort(-score,kind='stable')\n for ri,uid in enumerate(u):\n  ok=np.unpackbits(p[ri],count=len(items),bitorder='little').astype(bool)\n  sel=order[ok[order]][:100]\n  rows.extend((int(uid),int(items[j]),k+1) for k,j in enumerate(sel))\n out=f'{O}/{name}_validation.parquet'; pd.DataFrame(rows,columns=['uid','item_id','rank']).to_parquet(out,index=False)\n print(name,out)\nPY\nfor f in /app/solution/*_validation.parquet; do /opt/task-venv/bin/python /task/evaluate_public.py \"$f\" | tr '\\n' ' '; echo; done"
              ],
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              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python - <<'PY'\nimport pandas as pd, numpy as np, subprocess, json\nD='/task/data'; O='/app/solution'\nc=pd.read_parquet(D+'/candidate_catalog.parquet').sort_values('popularity_rank').reset_index(drop=True)\nprint(c.columns, c.head())\nz=np.load(D+'/validation_eligible_candidates.npz'); u=z['uids']; items=z['item_ids']; p=z['packed_eligible']; assert np.array_equal(items,c.item_id)\nmetrics={'poprank':-c.popularity_rank.to_numpy(), 'positive':c.positive_listens.to_numpy(), 'organic':c.organic_positive_listens.to_numpy(), 'org_ratio':c.organic_positive_listens.to_numpy()/np.maximum(c.positive_listens.to_numpy(),1)}\nfor name,score in metrics.items():\n rows=[]\n order=np.argsort(-score,kind='stable')\n for ri,uid in enumerate(u):\n  ok=np.unpackbits(p[ri],count=len(items),bitorder='little').astype(bool)\n  sel=order[ok[order]][:100]\n  rows.extend((int(uid),int(items[j]),k+1) for k,j in enumerate(sel))\n out=f'{O}/{name}_validation.parquet'; pd.DataFrame(rows,columns=['uid','item_id','rank']).to_parquet(out,index=False)\n print(name,out)\nPY\nfor f in /app/solution/*_validation.parquet; do /opt/task-venv/bin/python /task/evaluate_public.py \"$f\" | tr '\\n' ' '; echo; done"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "Index(['item_id', 'positive_listens', 'organic_positive_listens',\n       'popularity_rank'],\n      dtype='object')    item_id  positive_listens  organic_positive_listens  popularity_rank\n0  5862961             26615                     20620                1\n1  6901374             25536                     17347                2\n2  5635052             24691                     17194                3\n3  3542184             24075                     17699                4\n4  9378983             24036                     18195                5\npoprank /app/solution/poprank_validation.parquet\npositive /app/solution/positive_validation.parquet\norganic /app/solution/organic_validation.parquet\norg_ratio /app/solution/org_ratio_validation.parquet\n{   \"model\": \"/app/solution/org_ratio_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.000347,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/organic_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 3.2e-05,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/poprank_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/positive_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/production_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.02128,     \"quality_users\": 4263   } } \n",
              "stderr": "",
              "aggregated_output": "Index(['item_id', 'positive_listens', 'organic_positive_listens',\n       'popularity_rank'],\n      dtype='object')    item_id  positive_listens  organic_positive_listens  popularity_rank\n0  5862961             26615                     20620                1\n1  6901374             25536                     17347                2\n2  5635052             24691                     17194                3\n3  3542184             24075                     17699                4\n4  9378983             24036                     18195                5\npoprank /app/solution/poprank_validation.parquet\npositive /app/solution/positive_validation.parquet\norganic /app/solution/organic_validation.parquet\norg_ratio /app/solution/org_ratio_validation.parquet\n{   \"model\": \"/app/solution/org_ratio_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.000347,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/organic_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 3.2e-05,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/poprank_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/positive_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/production_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.02128,     \"quality_users\": 4263   } } \n",
              "exit_code": 0,
              "duration": {
                "secs": 23,
                "nanos": 340936756
              },
              "formatted_output": "Index(['item_id', 'positive_listens', 'organic_positive_listens',\n       'popularity_rank'],\n      dtype='object')    item_id  positive_listens  organic_positive_listens  popularity_rank\n0  5862961             26615                     20620                1\n1  6901374             25536                     17347                2\n2  5635052             24691                     17194                3\n3  3542184             24075                     17699                4\n4  9378983             24036                     18195                5\npoprank /app/solution/poprank_validation.parquet\npositive /app/solution/positive_validation.parquet\norganic /app/solution/organic_validation.parquet\norg_ratio /app/solution/org_ratio_validation.parquet\n{   \"model\": \"/app/solution/org_ratio_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.000347,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/organic_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 3.2e-05,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/poprank_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/positive_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01071,     \"quality_users\": 4263   } } \n{   \"model\": \"/app/solution/production_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.02128,     \"quality_users\": 4263   } } \n"
            }
          }
        }
      ]
    },
    {
      "id": 29,
      "role": "agent",
      "timestamp": "2026-09-23T21:48:17.372Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T21:48:17.372Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:48:20.416Z",
          "callId": "call_WpqnP4KI7n0MEbi5VETy1ISR",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"sed -n '1260,1490p' /app/solution/train_current_model.py; sed -n '1490,1620p' /app/solution/train_current_model.py; sed -n '1785,1865p' /app/solution/train_current_model.py\",workdir:\"/app\",yield_time_ms:10000,max_output_tokens:26000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:48:20.486Z",
            "content": "Script completed\nWall time 0.1 seconds\nOutput:\n\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            optimizer.zero_grad(set_to_none=True)\n            statistics, sequence_gradient = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=True,\n            )\n            if sequence_gradient is None:\n                raise RuntimeError(\"training block omitted its sequence gradient\")\n            sequence_vectors.backward(sequence_gradient)\n            nn.utils.clip_grad_norm_(model.parameters(), config.gradient_clip)\n            optimizer.step()\n\n            count = len(positive_items)\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += count\n            total_weight += statistics[\"weight_sum\"]\n            total_positive += statistics[\"positive_sum\"]\n            total_negative += statistics[\"negative_sum\"]\n            total_pair_correct += statistics[\"pair_correct\"]\n            batches += 1\n            if batches % 25 == 0:\n                release_accelerator_cache(device)\n            if batches % 250 == 0:\n                batch_bce = statistics[\"loss_sum\"] / max(\n                    statistics[\"weight_sum\"], 1.0e-12\n                )\n                running_bce = total_loss / max(total_weight, 1.0e-12)\n                log(\n                    f\"epoch={epoch}/{config.epochs} batches={batches:,} \"\n                    f\"targets={total_targets:,} \"\n                    f\"batch_bce={batch_bce:.6f} \"\n                    f\"running_bce={running_bce:.6f} \"\n                    f\"elapsed={time.monotonic() - started:.1f}s\"\n                )\n\n    return {\n        \"epoch\": float(epoch),\n        \"loss\": total_loss / max(total_weight, 1.0e-12),\n        \"positive_logit\": total_positive / max(total_targets, 1),\n        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n        \"pair_accuracy\": total_pair_correct\n        / max(total_targets * negative_count, 1),\n        \"targets\": float(total_targets),\n        \"target_weight_sum\": total_weight,\n        \"batches\": float(batches),\n        \"seconds\": time.monotonic() - started,\n    }\n\n\n@torch.no_grad()\ndef evaluate_validation_bce(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    training_counts: np.ndarray,\n    validation_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    device: torch.device,\n) -> dict[str, float]:\n    \"\"\"Measure deterministic BCE on each user's chronological target suffix.\"\"\"\n    model.eval()\n    totals = training_counts + validation_counts\n    users_with_validation = np.flatnonzero(validation_counts > 0)\n    ordered = users_with_validation[\n        np.argsort(totals[users_with_validation], kind=\"stable\")\n    ]\n    groups = [\n        ordered[start : start + config.user_batch_size]\n        for start in range(0, len(ordered), config.user_batch_size)\n    ]\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 20_000)\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    started = time.monotonic()\n\n    for group_number, users in enumerate(groups, start=1):\n        group_totals = totals[users]\n        group_starts = training_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_totals.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_totals,\n                group_starts,\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0)\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            statistics, _ = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=False,\n            )\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += len(positive_items)\n            total_weight += statistics[\"weight_sum\"]\n        if group_number % 25 == 0:\n            release_accelerator_cache(device)\n    return {\n        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n        \"validation_targets\": float(total_targets),\n        \"validation_target_weight_sum\": total_weight,\n        \"validation_seconds\": time.monotonic() - started,\n    }\n\n\ndef snapshot_model(model: nn.Module) -> dict[str, torch.Tensor]:\n    return {\n        name: value.detach().cpu().clone()\n        name: value.detach().cpu().clone()\n        for name, value in model.state_dict().items()\n    }\n\n\ndef save_epoch_checkpoint(\n    checkpoint_dir: Path,\n    epoch: int,\n    model_state: dict[str, torch.Tensor],\n    config: Config,\n    diagnostics: dict[str, float],\n    optimizer: torch.optim.Optimizer,\n    generator: torch.Generator,\n) -> Path:\n    checkpoint_dir.mkdir(parents=True, exist_ok=True)\n    path = checkpoint_dir / f\"epoch-{epoch:02d}.pt\"\n    torch.save(\n        {\n            \"epoch\": epoch,\n            \"config\": asdict(config),\n            \"diagnostics\": diagnostics,\n            \"model_state\": model_state,\n            \"optimizer_state\": optimizer.state_dict(),\n            \"generator_state\": generator.get_state(),\n        },\n        path,\n    )\n    log(f\"saved epoch checkpoint: {path}\")\n    return path\n\n\ndef train_model(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    config: Config,\n    device: torch.device,\n    checkpoint_dir: Path | None,\n    resume_checkpoint: Path | None,\n) -> tuple[base.SequentialTwoTower, list[dict[str, float]]]:\n    partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    training_counts = partition.training_counts\n    validation_counts = partition.validation_counts\n    log(\n        f\"chronological BCE window: train={int(training_counts.sum()):,} \"\n        f\"validation={int(validation_counts.sum()):,} \"\n        f\"selected={partition.selected_count:,} \"\n        f\"discarded_old_targets={int(partition.window_starts.sum()):,} \"\n        f\"all={prepared.target_count:,}\"\n    )\n    model = base.SequentialTwoTower(prepared.item_features, model_config(config)).to(\n        device\n    )\n    optimizer = torch.optim.AdamW(\n        model.parameters(), lr=config.learning_rate, weight_decay=config.weight_decay\n    )\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 10_000)\n    item_correction = build_item_correction(\n        prepared,\n        config,\n        partition.window_starts,\n        training_counts,\n    )\n    target_weights = build_target_weights(\n        public,\n        stage,\n        prepared,\n        partition.history_training_counts,\n        config,\n    )\n    known_positive_packed = (\n        build_known_positive_filter(prepared, partition.history_training_counts)\n        if config.negative_filter_scope == \"full-training-history\"\n        else None\n    )\n    history: list[dict[str, float]] = []\n    best_loss = float(\"inf\")\n    best_epoch = 0\n    best_state: dict[str, torch.Tensor] | None = None\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n    config: Config,\n    device: torch.device,\n) -> torch.Tensor:\n    sequence_rows = prepared.inference_user_rows\n    lengths = np.where(\n        sequence_rows >= 0, prepared.lengths[np.maximum(sequence_rows, 0)], 0\n    )\n    ordered = np.argsort(lengths, kind=\"stable\")\n    result = torch.zeros(\n        len(sequence_rows), config.embedding_dim, dtype=torch.float32\n    )\n    for group_start in range(0, len(ordered), config.user_batch_size):\n        output_rows = ordered[group_start : group_start + config.user_batch_size]\n        rows = sequence_rows[output_rows]\n        group_lengths = lengths[output_rows]\n        hidden = torch.zeros(\n            1, len(output_rows), config.embedding_dim, device=device\n        )\n        for start in range(0, int(group_lengths.max(initial=0)), config.bptt_steps):\n            steps = min(\n                config.bptt_steps,\n                int(group_lengths.max(initial=0)) - start,\n            )\n            items = np.full(\n                (len(output_rows), steps),\n                len(prepared.item_ids),\n                dtype=np.uint16,\n            )\n            features = np.zeros((len(output_rows), steps, 3), dtype=np.float16)\n            counts = np.zeros(len(output_rows), dtype=np.int32)\n            for local_row, sequence_row in enumerate(rows):\n                if sequence_row < 0:\n                    continue\n                count = min(steps, max(int(group_lengths[local_row]) - start, 0))\n                if not count:\n                    continue\n                offset = int(prepared.offsets[sequence_row])\n                selected = slice(offset + start, offset + start + count)\n                items[local_row, :count] = prepared.sequence_items[selected]\n                features[local_row, :count] = prepared.event_features[selected]\n                counts[local_row] = count\n            outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(items.astype(np.int64)).to(device),\n                torch.from_numpy(features.astype(np.float32)).to(device),\n                hidden,\n            )\n            next_rows: list[torch.Tensor] = []\n            for local_row, count in enumerate(counts):\n                next_rows.append(\n                    outputs[local_row, count - 1]\n                    if count\n                    else hidden[0, local_row]\n                )\n            hidden = torch.stack(next_rows).unsqueeze(0)\n\n        liked_items = torch.from_numpy(\n            prepared.inference_liked_items[output_rows].astype(np.int64)\n        ).to(device)\n        disliked_items = torch.from_numpy(\n            prepared.inference_disliked_items[output_rows].astype(np.int64)\n        ).to(device)\n        queries = user_queries(\n            model,\n            hidden.squeeze(0),\n            model._mean_context_channel(liked_items),\n            model._mean_context_channel(disliked_items),\n            torch.from_numpy(\n                prepared.inference_user_features[output_rows].astype(np.float32)\n            ).to(device),\n        )\n        result[torch.from_numpy(output_rows.astype(np.int64))] = queries.cpu()\n    return result\n\n\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:48:20.464Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-6bd5374c-32c8-4dbc-9c51-0352bdb80099",
              "process_id": "17820",
              "command": [
                "/bin/sh",
                "-lc",
                "sed -n '1260,1490p' /app/solution/train_current_model.py; sed -n '1490,1620p' /app/solution/train_current_model.py; sed -n '1785,1865p' /app/solution/train_current_model.py"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "read",
                  "cmd": "sed -n '1260,1490p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                },
                {
                  "type": "read",
                  "cmd": "sed -n '1490,1620p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                },
                {
                  "type": "read",
                  "cmd": "sed -n '1785,1865p' /app/solution/train_current_model.py",
                  "name": "train_current_model.py",
                  "path": "/app/solution/train_current_model.py"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            optimizer.zero_grad(set_to_none=True)\n            statistics, sequence_gradient = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=True,\n            )\n            if sequence_gradient is None:\n                raise RuntimeError(\"training block omitted its sequence gradient\")\n            sequence_vectors.backward(sequence_gradient)\n            nn.utils.clip_grad_norm_(model.parameters(), config.gradient_clip)\n            optimizer.step()\n\n            count = len(positive_items)\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += count\n            total_weight += statistics[\"weight_sum\"]\n            total_positive += statistics[\"positive_sum\"]\n            total_negative += statistics[\"negative_sum\"]\n            total_pair_correct += statistics[\"pair_correct\"]\n            batches += 1\n            if batches % 25 == 0:\n                release_accelerator_cache(device)\n            if batches % 250 == 0:\n                batch_bce = statistics[\"loss_sum\"] / max(\n                    statistics[\"weight_sum\"], 1.0e-12\n                )\n                running_bce = total_loss / max(total_weight, 1.0e-12)\n                log(\n                    f\"epoch={epoch}/{config.epochs} batches={batches:,} \"\n                    f\"targets={total_targets:,} \"\n                    f\"batch_bce={batch_bce:.6f} \"\n                    f\"running_bce={running_bce:.6f} \"\n                    f\"elapsed={time.monotonic() - started:.1f}s\"\n                )\n\n    return {\n        \"epoch\": float(epoch),\n        \"loss\": total_loss / max(total_weight, 1.0e-12),\n        \"positive_logit\": total_positive / max(total_targets, 1),\n        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n        \"pair_accuracy\": total_pair_correct\n        / max(total_targets * negative_count, 1),\n        \"targets\": float(total_targets),\n        \"target_weight_sum\": total_weight,\n        \"batches\": float(batches),\n        \"seconds\": time.monotonic() - started,\n    }\n\n\n@torch.no_grad()\ndef evaluate_validation_bce(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    training_counts: np.ndarray,\n    validation_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    device: torch.device,\n) -> dict[str, float]:\n    \"\"\"Measure deterministic BCE on each user's chronological target suffix.\"\"\"\n    model.eval()\n    totals = training_counts + validation_counts\n    users_with_validation = np.flatnonzero(validation_counts > 0)\n    ordered = users_with_validation[\n        np.argsort(totals[users_with_validation], kind=\"stable\")\n    ]\n    groups = [\n        ordered[start : start + config.user_batch_size]\n        for start in range(0, len(ordered), config.user_batch_size)\n    ]\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 20_000)\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    started = time.monotonic()\n\n    for group_number, users in enumerate(groups, start=1):\n        group_totals = totals[users]\n        group_starts = training_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_totals.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_totals,\n                group_starts,\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0)\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            statistics, _ = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=False,\n            )\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += len(positive_items)\n            total_weight += statistics[\"weight_sum\"]\n        if group_number % 25 == 0:\n            release_accelerator_cache(device)\n    return {\n        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n        \"validation_targets\": float(total_targets),\n        \"validation_target_weight_sum\": total_weight,\n        \"validation_seconds\": time.monotonic() - started,\n    }\n\n\ndef snapshot_model(model: nn.Module) -> dict[str, torch.Tensor]:\n    return {\n        name: value.detach().cpu().clone()\n        name: value.detach().cpu().clone()\n        for name, value in model.state_dict().items()\n    }\n\n\ndef save_epoch_checkpoint(\n    checkpoint_dir: Path,\n    epoch: int,\n    model_state: dict[str, torch.Tensor],\n    config: Config,\n    diagnostics: dict[str, float],\n    optimizer: torch.optim.Optimizer,\n    generator: torch.Generator,\n) -> Path:\n    checkpoint_dir.mkdir(parents=True, exist_ok=True)\n    path = checkpoint_dir / f\"epoch-{epoch:02d}.pt\"\n    torch.save(\n        {\n            \"epoch\": epoch,\n            \"config\": asdict(config),\n            \"diagnostics\": diagnostics,\n            \"model_state\": model_state,\n            \"optimizer_state\": optimizer.state_dict(),\n            \"generator_state\": generator.get_state(),\n        },\n        path,\n    )\n    log(f\"saved epoch checkpoint: {path}\")\n    return path\n\n\ndef train_model(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    config: Config,\n    device: torch.device,\n    checkpoint_dir: Path | None,\n    resume_checkpoint: Path | None,\n) -> tuple[base.SequentialTwoTower, list[dict[str, float]]]:\n    partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    training_counts = partition.training_counts\n    validation_counts = partition.validation_counts\n    log(\n        f\"chronological BCE window: train={int(training_counts.sum()):,} \"\n        f\"validation={int(validation_counts.sum()):,} \"\n        f\"selected={partition.selected_count:,} \"\n        f\"discarded_old_targets={int(partition.window_starts.sum()):,} \"\n        f\"all={prepared.target_count:,}\"\n    )\n    model = base.SequentialTwoTower(prepared.item_features, model_config(config)).to(\n        device\n    )\n    optimizer = torch.optim.AdamW(\n        model.parameters(), lr=config.learning_rate, weight_decay=config.weight_decay\n    )\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 10_000)\n    item_correction = build_item_correction(\n        prepared,\n        config,\n        partition.window_starts,\n        training_counts,\n    )\n    target_weights = build_target_weights(\n        public,\n        stage,\n        prepared,\n        partition.history_training_counts,\n        config,\n    )\n    known_positive_packed = (\n        build_known_positive_filter(prepared, partition.history_training_counts)\n        if config.negative_filter_scope == \"full-training-history\"\n        else None\n    )\n    history: list[dict[str, float]] = []\n    best_loss = float(\"inf\")\n    best_epoch = 0\n    best_state: dict[str, torch.Tensor] | None = None\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n    config: Config,\n    device: torch.device,\n) -> torch.Tensor:\n    sequence_rows = prepared.inference_user_rows\n    lengths = np.where(\n        sequence_rows >= 0, prepared.lengths[np.maximum(sequence_rows, 0)], 0\n    )\n    ordered = np.argsort(lengths, kind=\"stable\")\n    result = torch.zeros(\n        len(sequence_rows), config.embedding_dim, dtype=torch.float32\n    )\n    for group_start in range(0, len(ordered), config.user_batch_size):\n        output_rows = ordered[group_start : group_start + config.user_batch_size]\n        rows = sequence_rows[output_rows]\n        group_lengths = lengths[output_rows]\n        hidden = torch.zeros(\n            1, len(output_rows), config.embedding_dim, device=device\n        )\n        for start in range(0, int(group_lengths.max(initial=0)), config.bptt_steps):\n            steps = min(\n                config.bptt_steps,\n                int(group_lengths.max(initial=0)) - start,\n            )\n            items = np.full(\n                (len(output_rows), steps),\n                len(prepared.item_ids),\n                dtype=np.uint16,\n            )\n            features = np.zeros((len(output_rows), steps, 3), dtype=np.float16)\n            counts = np.zeros(len(output_rows), dtype=np.int32)\n            for local_row, sequence_row in enumerate(rows):\n                if sequence_row < 0:\n                    continue\n                count = min(steps, max(int(group_lengths[local_row]) - start, 0))\n                if not count:\n                    continue\n                offset = int(prepared.offsets[sequence_row])\n                selected = slice(offset + start, offset + start + count)\n                items[local_row, :count] = prepared.sequence_items[selected]\n                features[local_row, :count] = prepared.event_features[selected]\n                counts[local_row] = count\n            outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(items.astype(np.int64)).to(device),\n                torch.from_numpy(features.astype(np.float32)).to(device),\n                hidden,\n            )\n            next_rows: list[torch.Tensor] = []\n            for local_row, count in enumerate(counts):\n                next_rows.append(\n                    outputs[local_row, count - 1]\n                    if count\n                    else hidden[0, local_row]\n                )\n            hidden = torch.stack(next_rows).unsqueeze(0)\n\n        liked_items = torch.from_numpy(\n            prepared.inference_liked_items[output_rows].astype(np.int64)\n        ).to(device)\n        disliked_items = torch.from_numpy(\n            prepared.inference_disliked_items[output_rows].astype(np.int64)\n        ).to(device)\n        queries = user_queries(\n            model,\n            hidden.squeeze(0),\n            model._mean_context_channel(liked_items),\n            model._mean_context_channel(disliked_items),\n            torch.from_numpy(\n                prepared.inference_user_features[output_rows].astype(np.float32)\n            ).to(device),\n        )\n        result[torch.from_numpy(output_rows.astype(np.int64))] = queries.cpu()\n    return result\n\n\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n",
              "stderr": "",
              "aggregated_output": "                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            optimizer.zero_grad(set_to_none=True)\n            statistics, sequence_gradient = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=True,\n            )\n            if sequence_gradient is None:\n                raise RuntimeError(\"training block omitted its sequence gradient\")\n            sequence_vectors.backward(sequence_gradient)\n            nn.utils.clip_grad_norm_(model.parameters(), config.gradient_clip)\n            optimizer.step()\n\n            count = len(positive_items)\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += count\n            total_weight += statistics[\"weight_sum\"]\n            total_positive += statistics[\"positive_sum\"]\n            total_negative += statistics[\"negative_sum\"]\n            total_pair_correct += statistics[\"pair_correct\"]\n            batches += 1\n            if batches % 25 == 0:\n                release_accelerator_cache(device)\n            if batches % 250 == 0:\n                batch_bce = statistics[\"loss_sum\"] / max(\n                    statistics[\"weight_sum\"], 1.0e-12\n                )\n                running_bce = total_loss / max(total_weight, 1.0e-12)\n                log(\n                    f\"epoch={epoch}/{config.epochs} batches={batches:,} \"\n                    f\"targets={total_targets:,} \"\n                    f\"batch_bce={batch_bce:.6f} \"\n                    f\"running_bce={running_bce:.6f} \"\n                    f\"elapsed={time.monotonic() - started:.1f}s\"\n                )\n\n    return {\n        \"epoch\": float(epoch),\n        \"loss\": total_loss / max(total_weight, 1.0e-12),\n        \"positive_logit\": total_positive / max(total_targets, 1),\n        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n        \"pair_accuracy\": total_pair_correct\n        / max(total_targets * negative_count, 1),\n        \"targets\": float(total_targets),\n        \"target_weight_sum\": total_weight,\n        \"batches\": float(batches),\n        \"seconds\": time.monotonic() - started,\n    }\n\n\n@torch.no_grad()\ndef evaluate_validation_bce(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    training_counts: np.ndarray,\n    validation_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    device: torch.device,\n) -> dict[str, float]:\n    \"\"\"Measure deterministic BCE on each user's chronological target suffix.\"\"\"\n    model.eval()\n    totals = training_counts + validation_counts\n    users_with_validation = np.flatnonzero(validation_counts > 0)\n    ordered = users_with_validation[\n        np.argsort(totals[users_with_validation], kind=\"stable\")\n    ]\n    groups = [\n        ordered[start : start + config.user_batch_size]\n        for start in range(0, len(ordered), config.user_batch_size)\n    ]\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 20_000)\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    started = time.monotonic()\n\n    for group_number, users in enumerate(groups, start=1):\n        group_totals = totals[users]\n        group_starts = training_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_totals.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_totals,\n                group_starts,\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0)\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            statistics, _ = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=False,\n            )\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += len(positive_items)\n            total_weight += statistics[\"weight_sum\"]\n        if group_number % 25 == 0:\n            release_accelerator_cache(device)\n    return {\n        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n        \"validation_targets\": float(total_targets),\n        \"validation_target_weight_sum\": total_weight,\n        \"validation_seconds\": time.monotonic() - started,\n    }\n\n\ndef snapshot_model(model: nn.Module) -> dict[str, torch.Tensor]:\n    return {\n        name: value.detach().cpu().clone()\n        name: value.detach().cpu().clone()\n        for name, value in model.state_dict().items()\n    }\n\n\ndef save_epoch_checkpoint(\n    checkpoint_dir: Path,\n    epoch: int,\n    model_state: dict[str, torch.Tensor],\n    config: Config,\n    diagnostics: dict[str, float],\n    optimizer: torch.optim.Optimizer,\n    generator: torch.Generator,\n) -> Path:\n    checkpoint_dir.mkdir(parents=True, exist_ok=True)\n    path = checkpoint_dir / f\"epoch-{epoch:02d}.pt\"\n    torch.save(\n        {\n            \"epoch\": epoch,\n            \"config\": asdict(config),\n            \"diagnostics\": diagnostics,\n            \"model_state\": model_state,\n            \"optimizer_state\": optimizer.state_dict(),\n            \"generator_state\": generator.get_state(),\n        },\n        path,\n    )\n    log(f\"saved epoch checkpoint: {path}\")\n    return path\n\n\ndef train_model(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    config: Config,\n    device: torch.device,\n    checkpoint_dir: Path | None,\n    resume_checkpoint: Path | None,\n) -> tuple[base.SequentialTwoTower, list[dict[str, float]]]:\n    partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    training_counts = partition.training_counts\n    validation_counts = partition.validation_counts\n    log(\n        f\"chronological BCE window: train={int(training_counts.sum()):,} \"\n        f\"validation={int(validation_counts.sum()):,} \"\n        f\"selected={partition.selected_count:,} \"\n        f\"discarded_old_targets={int(partition.window_starts.sum()):,} \"\n        f\"all={prepared.target_count:,}\"\n    )\n    model = base.SequentialTwoTower(prepared.item_features, model_config(config)).to(\n        device\n    )\n    optimizer = torch.optim.AdamW(\n        model.parameters(), lr=config.learning_rate, weight_decay=config.weight_decay\n    )\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 10_000)\n    item_correction = build_item_correction(\n        prepared,\n        config,\n        partition.window_starts,\n        training_counts,\n    )\n    target_weights = build_target_weights(\n        public,\n        stage,\n        prepared,\n        partition.history_training_counts,\n        config,\n    )\n    known_positive_packed = (\n        build_known_positive_filter(prepared, partition.history_training_counts)\n        if config.negative_filter_scope == \"full-training-history\"\n        else None\n    )\n    history: list[dict[str, float]] = []\n    best_loss = float(\"inf\")\n    best_epoch = 0\n    best_state: dict[str, torch.Tensor] | None = None\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n    config: Config,\n    device: torch.device,\n) -> torch.Tensor:\n    sequence_rows = prepared.inference_user_rows\n    lengths = np.where(\n        sequence_rows >= 0, prepared.lengths[np.maximum(sequence_rows, 0)], 0\n    )\n    ordered = np.argsort(lengths, kind=\"stable\")\n    result = torch.zeros(\n        len(sequence_rows), config.embedding_dim, dtype=torch.float32\n    )\n    for group_start in range(0, len(ordered), config.user_batch_size):\n        output_rows = ordered[group_start : group_start + config.user_batch_size]\n        rows = sequence_rows[output_rows]\n        group_lengths = lengths[output_rows]\n        hidden = torch.zeros(\n            1, len(output_rows), config.embedding_dim, device=device\n        )\n        for start in range(0, int(group_lengths.max(initial=0)), config.bptt_steps):\n            steps = min(\n                config.bptt_steps,\n                int(group_lengths.max(initial=0)) - start,\n            )\n            items = np.full(\n                (len(output_rows), steps),\n                len(prepared.item_ids),\n                dtype=np.uint16,\n            )\n            features = np.zeros((len(output_rows), steps, 3), dtype=np.float16)\n            counts = np.zeros(len(output_rows), dtype=np.int32)\n            for local_row, sequence_row in enumerate(rows):\n                if sequence_row < 0:\n                    continue\n                count = min(steps, max(int(group_lengths[local_row]) - start, 0))\n                if not count:\n                    continue\n                offset = int(prepared.offsets[sequence_row])\n                selected = slice(offset + start, offset + start + count)\n                items[local_row, :count] = prepared.sequence_items[selected]\n                features[local_row, :count] = prepared.event_features[selected]\n                counts[local_row] = count\n            outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(items.astype(np.int64)).to(device),\n                torch.from_numpy(features.astype(np.float32)).to(device),\n                hidden,\n            )\n            next_rows: list[torch.Tensor] = []\n            for local_row, count in enumerate(counts):\n                next_rows.append(\n                    outputs[local_row, count - 1]\n                    if count\n                    else hidden[0, local_row]\n                )\n            hidden = torch.stack(next_rows).unsqueeze(0)\n\n        liked_items = torch.from_numpy(\n            prepared.inference_liked_items[output_rows].astype(np.int64)\n        ).to(device)\n        disliked_items = torch.from_numpy(\n            prepared.inference_disliked_items[output_rows].astype(np.int64)\n        ).to(device)\n        queries = user_queries(\n            model,\n            hidden.squeeze(0),\n            model._mean_context_channel(liked_items),\n            model._mean_context_channel(disliked_items),\n            torch.from_numpy(\n                prepared.inference_user_features[output_rows].astype(np.float32)\n            ).to(device),\n        )\n        result[torch.from_numpy(output_rows.astype(np.int64))] = queries.cpu()\n    return result\n\n\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n",
              "exit_code": 0,
              "duration": {
                "secs": 0,
                "nanos": 4960
              },
              "formatted_output": "                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0).detach()\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            optimizer.zero_grad(set_to_none=True)\n            statistics, sequence_gradient = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=True,\n            )\n            if sequence_gradient is None:\n                raise RuntimeError(\"training block omitted its sequence gradient\")\n            sequence_vectors.backward(sequence_gradient)\n            nn.utils.clip_grad_norm_(model.parameters(), config.gradient_clip)\n            optimizer.step()\n\n            count = len(positive_items)\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += count\n            total_weight += statistics[\"weight_sum\"]\n            total_positive += statistics[\"positive_sum\"]\n            total_negative += statistics[\"negative_sum\"]\n            total_pair_correct += statistics[\"pair_correct\"]\n            batches += 1\n            if batches % 25 == 0:\n                release_accelerator_cache(device)\n            if batches % 250 == 0:\n                batch_bce = statistics[\"loss_sum\"] / max(\n                    statistics[\"weight_sum\"], 1.0e-12\n                )\n                running_bce = total_loss / max(total_weight, 1.0e-12)\n                log(\n                    f\"epoch={epoch}/{config.epochs} batches={batches:,} \"\n                    f\"targets={total_targets:,} \"\n                    f\"batch_bce={batch_bce:.6f} \"\n                    f\"running_bce={running_bce:.6f} \"\n                    f\"elapsed={time.monotonic() - started:.1f}s\"\n                )\n\n    return {\n        \"epoch\": float(epoch),\n        \"loss\": total_loss / max(total_weight, 1.0e-12),\n        \"positive_logit\": total_positive / max(total_targets, 1),\n        \"negative_logit\": total_negative / max(total_targets * negative_count, 1),\n        \"pair_accuracy\": total_pair_correct\n        / max(total_targets * negative_count, 1),\n        \"targets\": float(total_targets),\n        \"target_weight_sum\": total_weight,\n        \"batches\": float(batches),\n        \"seconds\": time.monotonic() - started,\n    }\n\n\n@torch.no_grad()\ndef evaluate_validation_bce(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    config: Config,\n    target_weights: np.ndarray,\n    window_starts: np.ndarray,\n    training_counts: np.ndarray,\n    validation_counts: np.ndarray,\n    item_correction: torch.Tensor,\n    known_positive_packed: np.ndarray | None,\n    device: torch.device,\n) -> dict[str, float]:\n    \"\"\"Measure deterministic BCE on each user's chronological target suffix.\"\"\"\n    model.eval()\n    totals = training_counts + validation_counts\n    users_with_validation = np.flatnonzero(validation_counts > 0)\n    ordered = users_with_validation[\n        np.argsort(totals[users_with_validation], kind=\"stable\")\n    ]\n    groups = [\n        ordered[start : start + config.user_batch_size]\n        for start in range(0, len(ordered), config.user_batch_size)\n    ]\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 20_000)\n    total_loss = 0.0\n    total_targets = 0\n    total_weight = 0.0\n    started = time.monotonic()\n\n    for group_number, users in enumerate(groups, start=1):\n        group_totals = totals[users]\n        group_starts = training_counts[users]\n        hidden = torch.zeros(\n            1, len(users), config.embedding_dim, device=device\n        )\n        max_targets = int(group_totals.max())\n        for start in range(0, max_targets, config.bptt_steps):\n            steps = min(config.bptt_steps, max_targets - start)\n            block = build_dense_block(\n                prepared,\n                target_weights,\n                users,\n                window_starts[users],\n                group_totals,\n                group_starts,\n                start,\n                steps,\n                config,\n            )\n            sequence_outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(block[0].astype(np.int64)).to(device),\n                torch.from_numpy(block[1].astype(np.float32)).to(device),\n                hidden,\n            )\n            hidden = torch.stack(\n                [\n                    sequence_outputs[row, count - 1]\n                    if count\n                    else hidden[0, row]\n                    for row, count in enumerate(block[7])\n                ]\n            ).unsqueeze(0)\n            flat_scored = block[5].reshape(-1)\n            if not np.any(flat_scored):\n                continue\n            mask = torch.from_numpy(flat_scored).to(device)\n            sequence_vectors = sequence_outputs.reshape(\n                -1, config.embedding_dim\n            )[mask]\n            flat_states = block[3].reshape(-1)[flat_scored]\n            positive_items = torch.from_numpy(\n                block[4].reshape(-1)[flat_scored].astype(np.int64)\n            ).to(device)\n            known_history = torch.from_numpy(\n                block[6].reshape(-1, config.bptt_steps)[flat_scored].astype(\n                    np.int64\n                )\n            ).to(device)\n            liked_items = torch.from_numpy(\n                prepared.liked_states[flat_states].astype(np.int64)\n            ).to(device)\n            flat_user_rows = np.broadcast_to(\n                users[:, None], block[5].shape\n            ).reshape(-1)[flat_scored]\n            negatives, negative_weights = draw_training_negatives(\n                positive_items,\n                known_history,\n                liked_items,\n                flat_user_rows,\n                known_positive_packed,\n                prepared,\n                config,\n                item_correction,\n                generator,\n                device,\n            )\n            statistics, _ = score_target_microbatches(\n                model,\n                prepared,\n                config,\n                sequence_vectors,\n                flat_states,\n                block[2].reshape(-1, 4)[flat_scored].astype(np.float32),\n                positive_items,\n                negatives,\n                negative_weights,\n                block[8].reshape(-1)[flat_scored],\n                device,\n                backward=False,\n            )\n            total_loss += statistics[\"loss_sum\"]\n            total_targets += len(positive_items)\n            total_weight += statistics[\"weight_sum\"]\n        if group_number % 25 == 0:\n            release_accelerator_cache(device)\n    return {\n        \"validation_loss\": total_loss / max(total_weight, 1.0e-12),\n        \"validation_targets\": float(total_targets),\n        \"validation_target_weight_sum\": total_weight,\n        \"validation_seconds\": time.monotonic() - started,\n    }\n\n\ndef snapshot_model(model: nn.Module) -> dict[str, torch.Tensor]:\n    return {\n        name: value.detach().cpu().clone()\n        name: value.detach().cpu().clone()\n        for name, value in model.state_dict().items()\n    }\n\n\ndef save_epoch_checkpoint(\n    checkpoint_dir: Path,\n    epoch: int,\n    model_state: dict[str, torch.Tensor],\n    config: Config,\n    diagnostics: dict[str, float],\n    optimizer: torch.optim.Optimizer,\n    generator: torch.Generator,\n) -> Path:\n    checkpoint_dir.mkdir(parents=True, exist_ok=True)\n    path = checkpoint_dir / f\"epoch-{epoch:02d}.pt\"\n    torch.save(\n        {\n            \"epoch\": epoch,\n            \"config\": asdict(config),\n            \"diagnostics\": diagnostics,\n            \"model_state\": model_state,\n            \"optimizer_state\": optimizer.state_dict(),\n            \"generator_state\": generator.get_state(),\n        },\n        path,\n    )\n    log(f\"saved epoch checkpoint: {path}\")\n    return path\n\n\ndef train_model(\n    public: Path,\n    stage: str,\n    prepared: SequenceData,\n    config: Config,\n    device: torch.device,\n    checkpoint_dir: Path | None,\n    resume_checkpoint: Path | None,\n) -> tuple[base.SequentialTwoTower, list[dict[str, float]]]:\n    partition = chronological_target_partition(\n        prepared,\n        config.validation_fraction,\n        config.max_train_targets_per_user,\n        config.max_validation_targets_per_user,\n    )\n    training_counts = partition.training_counts\n    validation_counts = partition.validation_counts\n    log(\n        f\"chronological BCE window: train={int(training_counts.sum()):,} \"\n        f\"validation={int(validation_counts.sum()):,} \"\n        f\"selected={partition.selected_count:,} \"\n        f\"discarded_old_targets={int(partition.window_starts.sum()):,} \"\n        f\"all={prepared.target_count:,}\"\n    )\n    model = base.SequentialTwoTower(prepared.item_features, model_config(config)).to(\n        device\n    )\n    optimizer = torch.optim.AdamW(\n        model.parameters(), lr=config.learning_rate, weight_decay=config.weight_decay\n    )\n    generator = torch.Generator(device=\"cpu\").manual_seed(config.seed + 10_000)\n    item_correction = build_item_correction(\n        prepared,\n        config,\n        partition.window_starts,\n        training_counts,\n    )\n    target_weights = build_target_weights(\n        public,\n        stage,\n        prepared,\n        partition.history_training_counts,\n        config,\n    )\n    known_positive_packed = (\n        build_known_positive_filter(prepared, partition.history_training_counts)\n        if config.negative_filter_scope == \"full-training-history\"\n        else None\n    )\n    history: list[dict[str, float]] = []\n    best_loss = float(\"inf\")\n    best_epoch = 0\n    best_state: dict[str, torch.Tensor] | None = None\n    epochs_without_improvement = 0\n    start_epoch = 0\n\n    if resume_checkpoint is not None:\n        payload = torch.load(\n            resume_checkpoint, map_location=device, weights_only=False\n        )\n        stored_config = payload.get(\"config\", {})\n        architecture_fields = (\n            \"bptt_steps\",\n            \"embedding_dim\",\n            \"hidden_dim\",\n            \"user_hidden_1\",\n            \"user_hidden_2\",\n            \"item_hidden_1\",\n            \"item_hidden_2\",\n        )\n        mismatches = {\n            name: (stored_config.get(name), getattr(config, name))\n            for name in architecture_fields\n            if stored_config.get(name) != getattr(config, name)\n        }\n        if mismatches:\n            raise RuntimeError(\n                f\"resume checkpoint architecture differs: {mismatches}\"\n            )\n        stored_filter_scope = stored_config.get(\n            \"negative_filter_scope\", \"last-100\"\n        )\n        stored_target_weighting = stored_config.get(\n            \"target_weighting\", \"uniform\"\n        )\n        stored_weight_values = (\n            stored_config.get(\"ordinary_target_weight\", 1.0),\n            stored_config.get(\"organic_strong_target_weight\", 1.0),\n            stored_config.get(\"organic_like_target_weight\", 3.0),\n            stored_config.get(\"discovery_horizon_days\", 7),\n        )\n        current_weight_values = (\n            config.ordinary_target_weight,\n            config.organic_strong_target_weight,\n            config.organic_like_target_weight,\n            config.discovery_horizon_days,\n        )\n        stored_window_values = (\n            stored_config.get(\"validation_fraction\", 0.10),\n            stored_config.get(\"max_train_targets_per_user\", 0),\n    config: Config,\n    device: torch.device,\n) -> torch.Tensor:\n    sequence_rows = prepared.inference_user_rows\n    lengths = np.where(\n        sequence_rows >= 0, prepared.lengths[np.maximum(sequence_rows, 0)], 0\n    )\n    ordered = np.argsort(lengths, kind=\"stable\")\n    result = torch.zeros(\n        len(sequence_rows), config.embedding_dim, dtype=torch.float32\n    )\n    for group_start in range(0, len(ordered), config.user_batch_size):\n        output_rows = ordered[group_start : group_start + config.user_batch_size]\n        rows = sequence_rows[output_rows]\n        group_lengths = lengths[output_rows]\n        hidden = torch.zeros(\n            1, len(output_rows), config.embedding_dim, device=device\n        )\n        for start in range(0, int(group_lengths.max(initial=0)), config.bptt_steps):\n            steps = min(\n                config.bptt_steps,\n                int(group_lengths.max(initial=0)) - start,\n            )\n            items = np.full(\n                (len(output_rows), steps),\n                len(prepared.item_ids),\n                dtype=np.uint16,\n            )\n            features = np.zeros((len(output_rows), steps, 3), dtype=np.float16)\n            counts = np.zeros(len(output_rows), dtype=np.int32)\n            for local_row, sequence_row in enumerate(rows):\n                if sequence_row < 0:\n                    continue\n                count = min(steps, max(int(group_lengths[local_row]) - start, 0))\n                if not count:\n                    continue\n                offset = int(prepared.offsets[sequence_row])\n                selected = slice(offset + start, offset + start + count)\n                items[local_row, :count] = prepared.sequence_items[selected]\n                features[local_row, :count] = prepared.event_features[selected]\n                counts[local_row] = count\n            outputs, _ = event_sequence(\n                model,\n                torch.from_numpy(items.astype(np.int64)).to(device),\n                torch.from_numpy(features.astype(np.float32)).to(device),\n                hidden,\n            )\n            next_rows: list[torch.Tensor] = []\n            for local_row, count in enumerate(counts):\n                next_rows.append(\n                    outputs[local_row, count - 1]\n                    if count\n                    else hidden[0, local_row]\n                )\n            hidden = torch.stack(next_rows).unsqueeze(0)\n\n        liked_items = torch.from_numpy(\n            prepared.inference_liked_items[output_rows].astype(np.int64)\n        ).to(device)\n        disliked_items = torch.from_numpy(\n            prepared.inference_disliked_items[output_rows].astype(np.int64)\n        ).to(device)\n        queries = user_queries(\n            model,\n            hidden.squeeze(0),\n            model._mean_context_channel(liked_items),\n            model._mean_context_channel(disliked_items),\n            torch.from_numpy(\n                prepared.inference_user_features[output_rows].astype(np.float32)\n            ).to(device),\n        )\n        result[torch.from_numpy(output_rows.astype(np.int64))] = queries.cpu()\n    return result\n\n\n@torch.inference_mode()\ndef rank_candidates(\n    model: base.SequentialTwoTower,\n    prepared: SequenceData,\n    eligibility: CandidateSet,\n    config: Config,\n"
            }
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            "turn_token_usage": {
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            "code": "const patch = \"*** Begin Patch\\n*** Add File: /app/solution/analyze_blends.py\\n+#!/usr/bin/env python3\\n+\\\"\\\"\\\"Development-only diagnostics for validation score calibration.\\\"\\\"\\\"\\n+from pathlib import Path\\n+import sys\\n+\\n+import numpy as np\\n+import pandas as pd\\n+import torch\\n+\\n+sys.path.insert(0, str(Path(__file__).parent))\\n+import train_current_model as train\\n+import two_tower_model as base\\n+\\n+\\n+def main() -> None:\\n+    torch.set_num_threads(8)\\n+    config = train.Config()\\n+    prepared = train.load_cache(Path(\\\"/app/solution/validation_cache.npz\\\"), \\\"validation\\\", config)\\n+    candidates = train.CandidateSet.read(Path(\\\"/task/data/validation_eligible_candidates.npz\\\"))\\n+    payload = torch.load(\\\"/app/solution/baseline_ckpt/epoch-01.pt\\\", map_location=\\\"cpu\\\", weights_only=False)\\n+    model = base.SequentialTwoTower(prepared.item_features, train.model_config(config))\\n+    model.load_state_dict(payload[\\\"model_state\\\"])\\n+    model.eval()\\n+    with torch.inference_mode():\\n+        queries = train.inference_queries(model, prepared, config, torch.device(\\\"cpu\\\"))\\n+        items = torch.cat([model.encode_items(torch.arange(s, min(s + 2048, len(prepared.item_ids))))\\n+                           for s in range(0, len(prepared.item_ids), 2048)])\\n+    logpop = np.log1p(pd.read_parquet(\\\"/task/data/candidate_catalog.parquet\\\")\\n+                     .sort_values(\\\"popularity_rank\\\").positive_listens.to_numpy(dtype=np.float32))\\n+    logpop = (logpop - logpop.mean()) / logpop.std()\\n+    for alpha in (-1.0, -0.5, -0.25, 0.0, 0.1, 0.25, 0.5, 1.0):\\n+        rows = []\\n+        for start in range(0, len(candidates.uids), 128):\\n+            end = min(start + 128, len(candidates.uids))\\n+            scores = (queries[start:end] @ items.T).numpy()\\n+            scores += alpha * logpop[None, :]\\n+            eligible = np.unpackbits(candidates.packed[start:end], axis=1,\\n+                                     count=len(items), bitorder=\\\"little\\\").astype(bool)\\n+            scores[~eligible] = -np.inf\\n+            selected = np.argpartition(scores, -100, axis=1)[:, -100:]\\n+            selected = np.take_along_axis(selected,\\n+                np.argsort(-np.take_along_axis(scores, selected, axis=1), axis=1), axis=1)\\n+            for local, columns in enumerate(selected):\\n+                uid = int(candidates.uids[start + local])\\n+                rows.extend((uid, int(prepared.item_ids[col]), rank)\\n+                            for rank, col in enumerate(columns, 1))\\n+        pd.DataFrame(rows, columns=[\\\"uid\\\", \\\"item_id\\\", \\\"rank\\\"]).to_parquet(\\n+            f\\\"/app/solution/blend_{alpha:+.2f}_validation.parquet\\\", index=False)\\n+\\n+\\n+if __name__ == \\\"__main__\\\":\\n+    main()\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
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                  "content": "#!/usr/bin/env python3\n\"\"\"Development-only diagnostics for validation score calibration.\"\"\"\nfrom pathlib import Path\nimport sys\n\nimport numpy as np\nimport pandas as pd\nimport torch\n\nsys.path.insert(0, str(Path(__file__).parent))\nimport train_current_model as train\nimport two_tower_model as base\n\n\ndef main() -> None:\n    torch.set_num_threads(8)\n    config = train.Config()\n    prepared = train.load_cache(Path(\"/app/solution/validation_cache.npz\"), \"validation\", config)\n    candidates = train.CandidateSet.read(Path(\"/task/data/validation_eligible_candidates.npz\"))\n    payload = torch.load(\"/app/solution/baseline_ckpt/epoch-01.pt\", map_location=\"cpu\", weights_only=False)\n    model = base.SequentialTwoTower(prepared.item_features, train.model_config(config))\n    model.load_state_dict(payload[\"model_state\"])\n    model.eval()\n    with torch.inference_mode():\n        queries = train.inference_queries(model, prepared, config, torch.device(\"cpu\"))\n        items = torch.cat([model.encode_items(torch.arange(s, min(s + 2048, len(prepared.item_ids))))\n                           for s in range(0, len(prepared.item_ids), 2048)])\n    logpop = np.log1p(pd.read_parquet(\"/task/data/candidate_catalog.parquet\")\n                     .sort_values(\"popularity_rank\").positive_listens.to_numpy(dtype=np.float32))\n    logpop = (logpop - logpop.mean()) / logpop.std()\n    for alpha in (-1.0, -0.5, -0.25, 0.0, 0.1, 0.25, 0.5, 1.0):\n        rows = []\n        for start in range(0, len(candidates.uids), 128):\n            end = min(start + 128, len(candidates.uids))\n            scores = (queries[start:end] @ items.T).numpy()\n            scores += alpha * logpop[None, :]\n            eligible = np.unpackbits(candidates.packed[start:end], axis=1,\n                                     count=len(items), bitorder=\"little\").astype(bool)\n            scores[~eligible] = -np.inf\n            selected = np.argpartition(scores, -100, axis=1)[:, -100:]\n            selected = np.take_along_axis(selected,\n                np.argsort(-np.take_along_axis(scores, selected, axis=1), axis=1), axis=1)\n            for local, columns in enumerate(selected):\n                uid = int(candidates.uids[start + local])\n                rows.extend((uid, int(prepared.item_ids[col]), rank)\n                            for rank, col in enumerate(columns, 1))\n        pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]).to_parquet(\n            f\"/app/solution/blend_{alpha:+.2f}_validation.parquet\", index=False)\n\n\nif __name__ == \"__main__\":\n    main()\n"
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              "stdout": "blend_+0.00_validation.parquet {   \"model\": \"/app/solution/blend_+0.00_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.02128,     \"quality_users\": 4263   } } \nblend_+0.10_validation.parquet {   \"model\": \"/app/solution/blend_+0.10_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01907,     \"quality_users\": 4263   } } \nblend_+0.25_validation.parquet {   \"model\": \"/app/solution/blend_+0.25_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.016105,     \"quality_users\": 4263   } } \nblend_+0.50_validation.parquet {   \"model\": \"/app/solution/blend_+0.50_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.014927,     \"quality_users\": 4263   } } \nblend_+1.00_validation.parquet {   \"model\": \"/app/solution/blend_+1.00_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.013667,     \"quality_users\": 4263   } } \nblend_-0.25_validation.parquet {   \"model\": \"/app/solution/blend_-0.25_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.022735,     \"quality_users\": 4263   } } \nblend_-0.50_validation.parquet {   \"model\": \"/app/solution/blend_-0.50_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.020468,     \"quality_users\": 4263   } } \nblend_-1.00_validation.parquet {   \"model\": \"/app/solution/blend_-1.00_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.011598,     \"quality_users\": 4263   } } \n",
              "stderr": "",
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              "exit_code": 0,
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              "formatted_output": "blend_+0.00_validation.parquet {   \"model\": \"/app/solution/blend_+0.00_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.02128,     \"quality_users\": 4263   } } \nblend_+0.10_validation.parquet {   \"model\": \"/app/solution/blend_+0.10_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.01907,     \"quality_users\": 4263   } } \nblend_+0.25_validation.parquet {   \"model\": \"/app/solution/blend_+0.25_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.016105,     \"quality_users\": 4263   } } \nblend_+0.50_validation.parquet {   \"model\": \"/app/solution/blend_+0.50_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.014927,     \"quality_users\": 4263   } } \nblend_+1.00_validation.parquet {   \"model\": \"/app/solution/blend_+1.00_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.013667,     \"quality_users\": 4263   } } \nblend_-0.25_validation.parquet {   \"model\": \"/app/solution/blend_-0.25_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.022735,     \"quality_users\": 4263   } } \nblend_-0.50_validation.parquet {   \"model\": \"/app/solution/blend_-0.50_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.020468,     \"quality_users\": 4263   } } \nblend_-1.00_validation.parquet {   \"model\": \"/app/solution/blend_-1.00_validation.parquet\",   \"scores\": {     \"quality_ndcg@10\": 0.011598,     \"quality_users\": 4263   } } \n"
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    },
    {
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      "timestamp": "2026-09-23T21:52:08.110Z",
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    {
      "id": 38,
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      "timestamp": "2026-09-23T21:52:17.008Z",
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          "timestamp": "2026-09-23T21:52:17.008Z",
          "text": ""
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T21:52:20.595Z",
          "text": "The diagnostic supports the objective diagnosis: adding more popularity prior hurts, while a modest popularity penalty raises public NDCG from 0.02128 to 0.022735. The baseline is over-ranking globally frequent items because uniform negatives almost never challenge them. I’m now fine-tuning with rank-weighted catalog negatives (more likely to sample plausible popular competitors), while retaining the full-history false-negative filter. This changes what the model learns rather than relying only on a post-hoc reranker."
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:52:38.437Z",
          "callId": "call_T85Wr6UybMMOHfqjDsycFu3u",
          "name": "exec",
          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n class Config:\\n@@\\n     inbatch_correction_max: float = 4.0\\n+    catalog_negative_power: float = 0.75\\n@@\\n def draw_full_history_filtered_negatives(\\n@@\\n ) -> tuple[torch.Tensor, torch.Tensor]:\\n-    \\\"\\\"\\\"Draw mixed negatives and reject all known public-training positives.\\\"\\\"\\\"\\n+    \\\"\\\"\\\"Draw mixed negatives and reject all known public-training positives.\\n+\\n+    Catalog rows are popularity ordered.  A positive power therefore changes\\n+    the formerly uniform proposal into a tempered popularity proposal.  We do\\n+    not importance-correct this part: these are deliberately contrastive hard\\n+    negatives for top-of-list discrimination, not a Monte Carlo estimate of a\\n+    uniform-catalog BCE.\\n+    \\\"\\\"\\\"\\n@@\\n-    uniform = torch.randint(\\n-        n_items,\\n-        (batch_size, config.uniform_negatives),\\n-        generator=generator,\\n-        device=\\\"cpu\\\",\\n-    )\\n+    proposal = torch.arange(1, n_items + 1, dtype=torch.float32).pow(\\n+        -config.catalog_negative_power\\n+    )\\n+    uniform = torch.multinomial(\\n+        proposal,\\n+        batch_size * config.uniform_negatives,\\n+        replacement=True,\\n+        generator=generator,\\n+    ).reshape(batch_size, config.uniform_negatives)\\n@@\\n-            filler = torch.randint(\\n-                n_items,\\n-                (batch_size, config.inbatch_negatives - corrected_count),\\n-                generator=generator,\\n-                device=\\\"cpu\\\",\\n-            )\\n+            filler = torch.multinomial(\\n+                proposal,\\n+                batch_size * (config.inbatch_negatives - corrected_count),\\n+                replacement=True,\\n+                generator=generator,\\n+            ).reshape(batch_size, config.inbatch_negatives - corrected_count)\\n@@\\n-        replacements = torch.randint(\\n-            n_items,\\n-            (int(invalid.sum()),),\\n-            generator=generator,\\n-            device=\\\"cpu\\\",\\n-        ).numpy()\\n+        replacements = torch.multinomial(\\n+            proposal,\\n+            int(invalid.sum()),\\n+            replacement=True,\\n+            generator=generator,\\n+        ).numpy()\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:52:38.509Z",
            "content": "Script failed\nWall time 0.0 seconds\nOutput:\n\nScript error:\nExit code: 1\nWall time: 0 seconds\nOutput:\nFailed to write file /app/solution/train_current_model.py\n",
            "isError": null
          }
        },
        {
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          "timestamp": "2026-09-23T21:52:38.448Z",
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              "type": "FileChange",
              "id": "exec-a9f492eb-ffe6-496c-9b4c-e7f75f72e8c7",
              "changes": {
                "/app/solution/train_current_model.py": {
                  "type": "update",
                  "unified_diff": "@@ -60,2 +60,3 @@\n     inbatch_correction_max: float = 4.0\n+    catalog_negative_power: float = 0.75\n     negative_filter_scope: str = \"full-training-history\"\n@@ -640,3 +641,10 @@\n ) -> tuple[torch.Tensor, torch.Tensor]:\n-    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n+    \"\"\"Draw mixed negatives and reject all known public-training positives.\n+\n+    Catalog rows are popularity ordered.  A positive power therefore changes\n+    the formerly uniform proposal into a tempered popularity proposal.  We do\n+    not importance-correct this part: these are deliberately contrastive hard\n+    negatives for top-of-list discrimination, not a Monte Carlo estimate of a\n+    uniform-catalog BCE.\n+    \"\"\"\n     targets_cpu = targets.detach().cpu().numpy().astype(np.int64, copy=False)\n@@ -644,8 +652,11 @@\n     batch_size = len(targets_cpu)\n-    uniform = torch.randint(\n-        n_items,\n-        (batch_size, config.uniform_negatives),\n-        generator=generator,\n-        device=\"cpu\",\n+    proposal = torch.arange(1, n_items + 1, dtype=torch.float32).pow(\n+        -config.catalog_negative_power\n     )\n+    uniform = torch.multinomial(\n+        proposal,\n+        batch_size * config.uniform_negatives,\n+        replacement=True,\n+        generator=generator,\n+    ).reshape(batch_size, config.uniform_negatives)\n     inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n@@ -672,8 +683,8 @@\n         if corrected_count < config.inbatch_negatives:\n-            filler = torch.randint(\n-                n_items,\n-                (batch_size, config.inbatch_negatives - corrected_count),\n+            filler = torch.multinomial(\n+                proposal,\n+                batch_size * (config.inbatch_negatives - corrected_count),\n+                replacement=True,\n                 generator=generator,\n-                device=\"cpu\",\n-            )\n+            ).reshape(batch_size, config.inbatch_negatives - corrected_count)\n             inbatch = torch.cat([inbatch, filler], dim=1)\n@@ -699,7 +710,7 @@\n             )\n-        replacements = torch.randint(\n-            n_items,\n-            (int(invalid.sum()),),\n+        replacements = torch.multinomial(\n+            proposal,\n+            int(invalid.sum()),\n+            replacement=True,\n             generator=generator,\n-            device=\"cpu\",\n         ).numpy()\n",
                  "move_path": null
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              "status": "failed",
              "stdout": "",
              "stderr": "Failed to write file /app/solution/train_current_model.py\n"
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            "code": "let{output,...rest}=await tools.exec_command({cmd:\"ls -l /app/solution/train_current_model.py; chmod u+w /app/solution/train_current_model.py /app/solution/two_tower_model.py /app/solution/analyze_blends.py\",workdir:\"/app\",yield_time_ms:10000,max_output_tokens:2000});text(rest);text(output)\n"
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          "result": {
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            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n{\"chunk_id\":\"98b905\",\"wall_time_seconds\":0.00000656,\"exit_code\":0,\"original_token_count\":21}\n-r--r--r-- 1 agent agent 80058 Sep 23 21:39 /app/solution/train_current_model.py\n",
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          "timestamp": "2026-09-23T21:52:49.612Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:53:06.898Z",
          "callId": "call_kTPSWZvjmGMs83emyYgggGBq",
          "name": "exec",
          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n     inbatch_correction_max: float = 4.0\\n+    catalog_negative_power: float = 0.75\\n@@\\n def draw_full_history_filtered_negatives(\\n@@\\n ) -> tuple[torch.Tensor, torch.Tensor]:\\n-    \\\"\\\"\\\"Draw mixed negatives and reject all known public-training positives.\\\"\\\"\\\"\\n+    \\\"\\\"\\\"Draw mixed negatives and reject all known public-training positives.\\n+\\n+    Catalog rows are popularity ordered. A positive power changes the formerly\\n+    uniform proposal into a tempered popularity proposal. We intentionally do\\n+    not importance-correct it: these are contrastive hard negatives for\\n+    top-of-list discrimination, not an estimate of uniform-catalog BCE.\\n+    \\\"\\\"\\\"\\n@@\\n-    uniform = torch.randint(\\n-        n_items,\\n-        (batch_size, config.uniform_negatives),\\n-        generator=generator,\\n-        device=\\\"cpu\\\",\\n-    )\\n+    proposal = torch.arange(1, n_items + 1, dtype=torch.float32).pow(\\n+        -config.catalog_negative_power\\n+    )\\n+    uniform = torch.multinomial(\\n+        proposal,\\n+        batch_size * config.uniform_negatives,\\n+        replacement=True,\\n+        generator=generator,\\n+    ).reshape(batch_size, config.uniform_negatives)\\n@@\\n-            filler = torch.randint(\\n-                n_items,\\n-                (batch_size, config.inbatch_negatives - corrected_count),\\n-                generator=generator,\\n-                device=\\\"cpu\\\",\\n-            )\\n+            filler = torch.multinomial(\\n+                proposal,\\n+                batch_size * (config.inbatch_negatives - corrected_count),\\n+                replacement=True,\\n+                generator=generator,\\n+            ).reshape(batch_size, config.inbatch_negatives - corrected_count)\\n@@\\n-        replacements = torch.randint(\\n-            n_items,\\n-            (int(invalid.sum()),),\\n-            generator=generator,\\n-            device=\\\"cpu\\\",\\n-        ).numpy()\\n+        replacements = torch.multinomial(\\n+            proposal,\\n+            int(invalid.sum()),\\n+            replacement=True,\\n+            generator=generator,\\n+        ).numpy()\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:53:06.957Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n{}",
            "isError": null
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          "data": {
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              "changes": {
                "/app/solution/train_current_model.py": {
                  "type": "update",
                  "unified_diff": "@@ -60,2 +60,3 @@\n     inbatch_correction_max: float = 4.0\n+    catalog_negative_power: float = 0.75\n     negative_filter_scope: str = \"full-training-history\"\n@@ -640,3 +641,9 @@\n ) -> tuple[torch.Tensor, torch.Tensor]:\n-    \"\"\"Draw mixed negatives and reject all known public-training positives.\"\"\"\n+    \"\"\"Draw mixed negatives and reject all known public-training positives.\n+\n+    Catalog rows are popularity ordered. A positive power changes the formerly\n+    uniform proposal into a tempered popularity proposal. We intentionally do\n+    not importance-correct it: these are contrastive hard negatives for\n+    top-of-list discrimination, not an estimate of uniform-catalog BCE.\n+    \"\"\"\n     targets_cpu = targets.detach().cpu().numpy().astype(np.int64, copy=False)\n@@ -644,8 +651,11 @@\n     batch_size = len(targets_cpu)\n-    uniform = torch.randint(\n-        n_items,\n-        (batch_size, config.uniform_negatives),\n+    proposal = torch.arange(1, n_items + 1, dtype=torch.float32).pow(\n+        -config.catalog_negative_power\n+    )\n+    uniform = torch.multinomial(\n+        proposal,\n+        batch_size * config.uniform_negatives,\n+        replacement=True,\n         generator=generator,\n-        device=\"cpu\",\n-    )\n+    ).reshape(batch_size, config.uniform_negatives)\n     inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n@@ -672,8 +682,8 @@\n         if corrected_count < config.inbatch_negatives:\n-            filler = torch.randint(\n-                n_items,\n-                (batch_size, config.inbatch_negatives - corrected_count),\n+            filler = torch.multinomial(\n+                proposal,\n+                batch_size * (config.inbatch_negatives - corrected_count),\n+                replacement=True,\n                 generator=generator,\n-                device=\"cpu\",\n-            )\n+            ).reshape(batch_size, config.inbatch_negatives - corrected_count)\n             inbatch = torch.cat([inbatch, filler], dim=1)\n@@ -699,7 +709,7 @@\n             )\n-        replacements = torch.randint(\n-            n_items,\n-            (int(invalid.sum()),),\n+        replacements = torch.multinomial(\n+            proposal,\n+            int(invalid.sum()),\n+            replacement=True,\n             generator=generator,\n-            device=\"cpu\",\n         ).numpy()\n",
                  "move_path": null
                }
              },
              "status": "completed",
              "stdout": "Success. Updated the following files:\nM /app/solution/train_current_model.py\n",
              "stderr": ""
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            "timestamp": "2026-09-23T21:59:00.536Z",
            "content": "Script completed\nWall time 25.4 seconds\nOutput:\n\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/hard_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 328.025,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.184243683999966,\n      \"validation_loss\": 0.7032223276589955\n    },\n    {\n      \"epoch\": 2.0,\n      \"loss\": 0.5223124136765135,\n      \"positive_logit\": 0.7131804463678048,\n      \"negative_logit\": -1.0540214789929792,\n      \"pair_accuracy\": 0.7869812327805704,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 212.61465647,\n      \"validation_loss\": 0.4827574864668113,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.826170461999936\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 2.008946418762207,\n    \"query_norm_std\": 0.8127394318580627,\n    \"item_norm_mean\": 2.4269871711730957,\n    \"item_norm_std\": 1.0597095489501953\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
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              "stdout": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nusing a fresh AdamW optimizer after loading /app/solution/baseline_ckpt/epoch-01.pt\nBCE objective changed: filter full-training-history->full-training-history, target weighting organic-strong->organic-strong, target window (0.1, 128, 16)->(0.1, 128, 16); recomputing the resume checkpoint's validation BCE\nresumed validation-BCE training: epoch=1 loss=0.703222\nepoch=2/2 batches=250 targets=987,417 batch_bce=0.483328 running_bce=0.524237 elapsed=199.2s\nsaved epoch checkpoint: /app/solution/hard_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.52231 validation_loss=0.48276 pair_accuracy=0.787 train_targets=1,052,953 validation_targets=130,103 train_seconds=212.6 validation_seconds=15.8\nrestored best validation-BCE checkpoint: epoch=2 loss=0.482757\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/hard_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 328.025,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.184243683999966,\n      \"validation_loss\": 0.7032223276589955\n    },\n    {\n      \"epoch\": 2.0,\n      \"loss\": 0.5223124136765135,\n      \"positive_logit\": 0.7131804463678048,\n      \"negative_logit\": -1.0540214789929792,\n      \"pair_accuracy\": 0.7869812327805704,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 212.61465647,\n      \"validation_loss\": 0.4827574864668113,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.826170461999936\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 2.008946418762207,\n    \"query_norm_std\": 0.8127394318580627,\n    \"item_norm_mean\": 2.4269871711730957,\n    \"item_norm_std\": 1.0597095489501953\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "stderr": "",
              "aggregated_output": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nusing a fresh AdamW optimizer after loading /app/solution/baseline_ckpt/epoch-01.pt\nBCE objective changed: filter full-training-history->full-training-history, target weighting organic-strong->organic-strong, target window (0.1, 128, 16)->(0.1, 128, 16); recomputing the resume checkpoint's validation BCE\nresumed validation-BCE training: epoch=1 loss=0.703222\nepoch=2/2 batches=250 targets=987,417 batch_bce=0.483328 running_bce=0.524237 elapsed=199.2s\nsaved epoch checkpoint: /app/solution/hard_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.52231 validation_loss=0.48276 pair_accuracy=0.787 train_targets=1,052,953 validation_targets=130,103 train_seconds=212.6 validation_seconds=15.8\nrestored best validation-BCE checkpoint: epoch=2 loss=0.482757\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/hard_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 328.025,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.184243683999966,\n      \"validation_loss\": 0.7032223276589955\n    },\n    {\n      \"epoch\": 2.0,\n      \"loss\": 0.5223124136765135,\n      \"positive_logit\": 0.7131804463678048,\n      \"negative_logit\": -1.0540214789929792,\n      \"pair_accuracy\": 0.7869812327805704,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 212.61465647,\n      \"validation_loss\": 0.4827574864668113,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.826170461999936\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 2.008946418762207,\n    \"query_norm_std\": 0.8127394318580627,\n    \"item_norm_mean\": 2.4269871711730957,\n    \"item_norm_std\": 1.0597095489501953\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "exit_code": 0,
              "duration": {
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              "formatted_output": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nusing a fresh AdamW optimizer after loading /app/solution/baseline_ckpt/epoch-01.pt\nBCE objective changed: filter full-training-history->full-training-history, target weighting organic-strong->organic-strong, target window (0.1, 128, 16)->(0.1, 128, 16); recomputing the resume checkpoint's validation BCE\nresumed validation-BCE training: epoch=1 loss=0.703222\nepoch=2/2 batches=250 targets=987,417 batch_bce=0.483328 running_bce=0.524237 elapsed=199.2s\nsaved epoch checkpoint: /app/solution/hard_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.52231 validation_loss=0.48276 pair_accuracy=0.787 train_targets=1,052,953 validation_targets=130,103 train_seconds=212.6 validation_seconds=15.8\nrestored best validation-BCE checkpoint: epoch=2 loss=0.482757\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/hard_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 328.025,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.184243683999966,\n      \"validation_loss\": 0.7032223276589955\n    },\n    {\n      \"epoch\": 2.0,\n      \"loss\": 0.5223124136765135,\n      \"positive_logit\": 0.7131804463678048,\n      \"negative_logit\": -1.0540214789929792,\n      \"pair_accuracy\": 0.7869812327805704,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 212.61465647,\n      \"validation_loss\": 0.4827574864668113,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.826170461999936\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 2.008946418762207,\n    \"query_norm_std\": 0.8127394318580627,\n    \"item_norm_mean\": 2.4269871711730957,\n    \"item_norm_std\": 1.0597095489501953\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n"
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            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python /task/evaluate_public.py /app/solution/hard_validation.parquet\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:3000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:59:08.630Z",
            "content": "Script completed\nWall time 3.4 seconds\nOutput:\n\n{\n  \"model\": \"/app/solution/hard_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.014692,\n    \"quality_users\": 4263\n  }\n}\n",
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              "stdout": "{\n  \"model\": \"/app/solution/hard_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.014692,\n    \"quality_users\": 4263\n  }\n}\n",
              "stderr": "",
              "aggregated_output": "{\n  \"model\": \"/app/solution/hard_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.014692,\n    \"quality_users\": 4263\n  }\n}\n",
              "exit_code": 0,
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    },
    {
      "id": 50,
      "role": "agent",
      "timestamp": "2026-09-23T21:59:18.136Z",
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          "text": ""
        },
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          "timestamp": "2026-09-23T21:59:21.466Z",
          "text": "The first hard-negative setting was too aggressive: it improved its own hard-negative BCE but dropped public NDCG to 0.014692, a useful confirmation that proposal bias must be controlled. I’m narrowing the change to a mixture—20 truly uniform negatives, four popularity-tempered hard negatives, and the existing eight in-batch examples—so the model keeps broad catalog calibration while receiving a small top-of-list learning signal. The baseline artifact remains preserved."
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:59:32.680Z",
          "callId": "call_ib0GsecvQR3SPLD9xVPAcPQ2",
          "name": "exec",
          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n     catalog_negative_power: float = 0.75\\n+    catalog_hard_negatives: int = 4\\n@@\\n-    uniform = torch.multinomial(\\n-        proposal,\\n-        batch_size * config.uniform_negatives,\\n-        replacement=True,\\n-        generator=generator,\\n-    ).reshape(batch_size, config.uniform_negatives)\\n+    hard_count = min(config.catalog_hard_negatives, config.uniform_negatives)\\n+    broad_count = config.uniform_negatives - hard_count\\n+    broad = torch.randint(\\n+        n_items,\\n+        (batch_size, broad_count),\\n+        generator=generator,\\n+        device=\\\"cpu\\\",\\n+    )\\n+    hard = torch.multinomial(\\n+        proposal,\\n+        batch_size * hard_count,\\n+        replacement=True,\\n+        generator=generator,\\n+    ).reshape(batch_size, hard_count)\\n+    uniform = torch.cat([broad, hard], dim=1)\\n@@\\n-        replacements = torch.multinomial(\\n-            proposal,\\n-            int(invalid.sum()),\\n-            replacement=True,\\n-            generator=generator,\\n-        ).numpy()\\n+        replacements = torch.randint(\\n+            n_items,\\n+            (int(invalid.sum()),),\\n+            generator=generator,\\n+            device=\\\"cpu\\\",\\n+        ).numpy()\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T21:59:32.763Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n{}",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T21:59:32.691Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "FileChange",
              "id": "exec-4fda6742-cb9f-4077-b431-ab31e0cb48c4",
              "changes": {
                "/app/solution/train_current_model.py": {
                  "type": "update",
                  "unified_diff": "@@ -61,2 +61,3 @@\n     catalog_negative_power: float = 0.75\n+    catalog_hard_negatives: int = 4\n     negative_filter_scope: str = \"full-training-history\"\n@@ -654,8 +655,17 @@\n     )\n-    uniform = torch.multinomial(\n+    hard_count = min(config.catalog_hard_negatives, config.uniform_negatives)\n+    broad_count = config.uniform_negatives - hard_count\n+    broad = torch.randint(\n+        n_items,\n+        (batch_size, broad_count),\n+        generator=generator,\n+        device=\"cpu\",\n+    )\n+    hard = torch.multinomial(\n         proposal,\n-        batch_size * config.uniform_negatives,\n+        batch_size * hard_count,\n         replacement=True,\n         generator=generator,\n-    ).reshape(batch_size, config.uniform_negatives)\n+    ).reshape(batch_size, hard_count)\n+    uniform = torch.cat([broad, hard], dim=1)\n     inbatch = torch.empty((batch_size, 0), dtype=torch.long)\n@@ -709,7 +719,7 @@\n             )\n-        replacements = torch.multinomial(\n-            proposal,\n-            int(invalid.sum()),\n-            replacement=True,\n+        replacements = torch.randint(\n+            n_items,\n+            (int(invalid.sum()),),\n             generator=generator,\n+            device=\"cpu\",\n         ).numpy()\n",
                  "move_path": null
                }
              },
              "status": "completed",
              "stdout": "Success. Updated the following files:\nM /app/solution/train_current_model.py\n",
              "stderr": ""
            }
          }
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    {
      "id": 51,
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      "timestamp": "2026-09-23T21:59:36.852Z",
      "blocks": [
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          "kind": "reasoning",
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          "timestamp": "2026-09-23T21:59:36.852Z",
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        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T21:59:43.275Z",
          "callId": "call_C1NhXtG3Zf98AECAlkOx9aKU",
          "name": "exec",
          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n     parser.add_argument(\\n         \\\"--catalog-negative-power\\\",\\n@@\\n         help=\\\"sample catalog negatives proportional to popularity_rank**(-power)\\\",\\n     )\\n+    parser.add_argument(\\n+        \\\"--catalog-hard-negatives\\\",\\n+        type=int,\\n+        default=Config.catalog_hard_negatives,\\n+        help=\\\"replace this many uniform slots with popularity-tempered negatives\\\",\\n+    )\\n@@\\n         or args.catalog_negative_power < 0\\n+        or args.catalog_hard_negatives < 0\\n+        or args.catalog_hard_negatives > Config.uniform_negatives\\n@@\\n         catalog_negative_power=args.catalog_negative_power,\\n+        catalog_hard_negatives=args.catalog_hard_negatives,\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
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            "content": "Script completed\nWall time 30.0 seconds\nOutput:\n\nsaved epoch checkpoint: /app/solution/mixed_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.47491 validation_loss=0.44878 pair_accuracy=0.815 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.7 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=2 loss=0.448780\n",
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          "result": {
            "timestamp": "2026-09-23T22:05:26.467Z",
            "content": "Script completed\nWall time 3.2 seconds\nOutput:\n\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 324.457,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.88138106800011,\n      \"validation_loss\": 0.5280008141948098\n    },\n    {\n      \"epoch\": 2.0,\n      \"loss\": 0.47490796765986815,\n      \"positive_logit\": 0.9606951888467167,\n      \"negative_logit\": -1.2908256485146337,\n      \"pair_accuracy\": 0.8145243959132079,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 209.68635990100006,\n      \"validation_loss\": 0.4487804816127016,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.422220467999978\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.8730192184448242,\n    \"query_norm_std\": 0.8192510604858398,\n    \"item_norm_mean\": 2.6219735145568848,\n    \"item_norm_std\": 1.1031395196914673\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
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          "data": {
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              "command": [
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              "stdout": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nusing a fresh AdamW optimizer after loading /app/solution/baseline_ckpt/epoch-01.pt\nBCE objective changed: filter full-training-history->full-training-history, target weighting organic-strong->organic-strong, target window (0.1, 128, 16)->(0.1, 128, 16); recomputing the resume checkpoint's validation BCE\nresumed validation-BCE training: epoch=1 loss=0.528001\nepoch=2/2 batches=250 targets=987,417 batch_bce=0.468015 running_bce=0.476167 elapsed=196.5s\nsaved epoch checkpoint: /app/solution/mixed_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.47491 validation_loss=0.44878 pair_accuracy=0.815 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.7 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=2 loss=0.448780\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 324.457,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5398380448679045,\n      \"positive_logit\": 0.742779958487847,\n      \"negative_logit\": -0.622224708539116,\n      \"pair_accuracy\": 0.7547733315257186,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 211.00416867299998,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.88138106800011,\n      \"validation_loss\": 0.5280008141948098\n    },\n    {\n      \"epoch\": 2.0,\n      \"loss\": 0.47490796765986815,\n      \"positive_logit\": 0.9606951888467167,\n      \"negative_logit\": -1.2908256485146337,\n      \"pair_accuracy\": 0.8145243959132079,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 209.68635990100006,\n      \"validation_loss\": 0.4487804816127016,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.422220467999978\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.8730192184448242,\n    \"query_norm_std\": 0.8192510604858398,\n    \"item_norm_mean\": 2.6219735145568848,\n    \"item_norm_std\": 1.1031395196914673\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "stderr": "",
              "aggregated_output": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nusing a fresh AdamW optimizer after loading /app/solution/baseline_ckpt/epoch-01.pt\nBCE objective changed: filter full-training-history->full-training-history, target weighting organic-strong->organic-strong, target window (0.1, 128, 16)->(0.1, 128, 16); recomputing the resume checkpoint's validation BCE\nresumed validation-BCE training: epoch=1 loss=0.528001\nepoch=2/2 batches=250 targets=987,417 batch_bce=0.468015 running_bce=0.476167 elapsed=196.5s\nsaved epoch checkpoint: /app/solution/mixed_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.47491 validation_loss=0.44878 pair_accuracy=0.815 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.7 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=2 loss=0.448780\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 324.457,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 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78769.25,\n      \"validation_seconds\": 15.422220467999978\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.8730192184448242,\n    \"query_norm_std\": 0.8192510604858398,\n    \"item_norm_mean\": 2.6219735145568848,\n    \"item_norm_std\": 1.1031395196914673\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "exit_code": 0,
              "duration": {
                "secs": 328,
                "nanos": 948386180
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              "formatted_output": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nusing a fresh AdamW optimizer after loading /app/solution/baseline_ckpt/epoch-01.pt\nBCE objective changed: filter full-training-history->full-training-history, target weighting organic-strong->organic-strong, target window (0.1, 128, 16)->(0.1, 128, 16); recomputing the resume checkpoint's validation BCE\nresumed validation-BCE training: epoch=1 loss=0.528001\nepoch=2/2 batches=250 targets=987,417 batch_bce=0.468015 running_bce=0.476167 elapsed=196.5s\nsaved epoch checkpoint: /app/solution/mixed_ckpt/epoch-02.pt\nepoch=2/2 train_loss=0.47491 validation_loss=0.44878 pair_accuracy=0.815 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.7 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=2 loss=0.448780\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 324.457,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 2,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 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            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python /task/evaluate_public.py /app/solution/mixed_validation.parquet\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:3000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:05:33.910Z",
            "content": "Script completed\nWall time 3.5 seconds\nOutput:\n\n{\n  \"model\": \"/app/solution/mixed_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.017814,\n    \"quality_users\": 4263\n  }\n}\n",
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              "status": "completed",
              "stdout": "{\n  \"model\": \"/app/solution/mixed_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.017814,\n    \"quality_users\": 4263\n  }\n}\n",
              "stderr": "",
              "aggregated_output": "{\n  \"model\": \"/app/solution/mixed_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.017814,\n    \"quality_users\": 4263\n  }\n}\n",
              "exit_code": 0,
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          "timestamp": "2026-09-23T22:05:52.716Z",
          "text": "The four-negative mixture also over-corrected after a full additional epoch (0.017814). The key confound is now evident: the production recipe intentionally stops after one epoch, and a second full-rate epoch changes item norms substantially. I’m preserving the measured baseline as the best trained checkpoint and using it to calibrate the two-tower score itself—testing item-vector norm control and a narrower popularity bias. Both remain indexable because they are item-side-only transformations (equivalently, precomputed item vectors/biases). In parallel, I’ll keep enough time for the required `train + val` refit."
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          "name": "exec",
          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/analyze_blends.py\\n@@\\n-    for alpha in (-1.0, -0.5, -0.25, 0.0, 0.1, 0.25, 0.5, 1.0):\\n+    item_norm = torch.linalg.vector_norm(items, dim=1).numpy()\\n+    settings = [\\n+        (\\\"pop_-0.10\\\", 0.10, 0.0),\\n+        (\\\"pop_-0.15\\\", 0.15, 0.0),\\n+        (\\\"pop_-0.20\\\", 0.20, 0.0),\\n+        (\\\"pop_-0.25\\\", 0.25, 0.0),\\n+        (\\\"pop_-0.30\\\", 0.30, 0.0),\\n+        (\\\"norm_0.25\\\", 0.0, 0.25),\\n+        (\\\"norm_0.50\\\", 0.0, 0.50),\\n+        (\\\"norm_0.75\\\", 0.0, 0.75),\\n+        (\\\"norm_1.00\\\", 0.0, 1.00),\\n+        (\\\"pop15_norm25\\\", 0.15, 0.25),\\n+        (\\\"pop20_norm25\\\", 0.20, 0.25),\\n+        (\\\"pop10_norm50\\\", 0.10, 0.50),\\n+    ]\\n+    for name, pop_penalty, norm_power in settings:\\n@@\\n-            scores = (queries[start:end] @ items.T).numpy()\\n-            scores += alpha * logpop[None, :]\\n+            scores = (queries[start:end] @ items.T).numpy()\\n+            scores /= item_norm[None, :] ** norm_power\\n+            scores -= pop_penalty * logpop[None, :]\\n@@\\n-            f\\\"/app/solution/blend_{alpha:+.2f}_validation.parquet\\\", index=False)\\n+            f\\\"/app/solution/cal_{name}_validation.parquet\\\", index=False)\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:06:10.624Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n{}",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:06:10.564Z",
          "data": {
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              "id": "exec-b6eb5685-3bf7-4a70-bd17-513c992722e0",
              "changes": {
                "/app/solution/analyze_blends.py": {
                  "type": "update",
                  "unified_diff": "@@ -30,3 +30,18 @@\n     logpop = (logpop - logpop.mean()) / logpop.std()\n-    for alpha in (-1.0, -0.5, -0.25, 0.0, 0.1, 0.25, 0.5, 1.0):\n+    item_norm = torch.linalg.vector_norm(items, dim=1).numpy()\n+    settings = [\n+        (\"pop_-0.10\", 0.10, 0.0),\n+        (\"pop_-0.15\", 0.15, 0.0),\n+        (\"pop_-0.20\", 0.20, 0.0),\n+        (\"pop_-0.25\", 0.25, 0.0),\n+        (\"pop_-0.30\", 0.30, 0.0),\n+        (\"norm_0.25\", 0.0, 0.25),\n+        (\"norm_0.50\", 0.0, 0.50),\n+        (\"norm_0.75\", 0.0, 0.75),\n+        (\"norm_1.00\", 0.0, 1.00),\n+        (\"pop15_norm25\", 0.15, 0.25),\n+        (\"pop20_norm25\", 0.20, 0.25),\n+        (\"pop10_norm50\", 0.10, 0.50),\n+    ]\n+    for name, pop_penalty, norm_power in settings:\n         rows = []\n@@ -35,3 +50,4 @@\n             scores = (queries[start:end] @ items.T).numpy()\n-            scores += alpha * logpop[None, :]\n+            scores /= item_norm[None, :] ** norm_power\n+            scores -= pop_penalty * logpop[None, :]\n             eligible = np.unpackbits(candidates.packed[start:end], axis=1,\n@@ -47,3 +63,3 @@\n         pd.DataFrame(rows, columns=[\"uid\", \"item_id\", \"rank\"]).to_parquet(\n-            f\"/app/solution/blend_{alpha:+.2f}_validation.parquet\", index=False)\n+            f\"/app/solution/cal_{name}_validation.parquet\", index=False)\n \n",
                  "move_path": null
                }
              },
              "status": "completed",
              "stdout": "Success. Updated the following files:\nM /app/solution/analyze_blends.py\n",
              "stderr": ""
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          },
          "result": {
            "timestamp": "2026-09-23T22:06:15.164Z",
            "content": "Script completed\nWall time 1.2 seconds\nOutput:\n\n{\"chunk_id\":\"f64739\",\"wall_time_seconds\":1.001162858,\"session_id\":82372,\"original_token_count\":0,\"output\":\"\"}",
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            "timestamp": "2026-09-23T22:15:03.968Z",
            "content": "Script completed\nWall time 8.4 seconds\nOutput:\n\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_fresh_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 308.105,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5630657875696798,\n      \"positive_logit\": 0.5603278407790796,\n      \"negative_logit\": -0.5557115211259555,\n      \"pair_accuracy\": 0.7370967353243687,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 209.92406160300015,\n      \"validation_loss\": 0.5159006883799406,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.369371893999869\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.4622777700424194,\n    \"query_norm_std\": 0.669554591178894,\n    \"item_norm_mean\": 1.9108951091766357,\n    \"item_norm_std\": 0.794044017791748\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
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              "command": [
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                "-lc",
                "/opt/task-venv/bin/python /app/solution/train_current_model.py --stage validation --public-dir /task --output /app/solution/mixed_fresh_validation.parquet --prepared-cache /app/solution/validation_cache.npz --checkpoint-dir /app/solution/mixed_fresh_ckpt --epochs 1 --threads 8"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python /app/solution/train_current_model.py --stage validation --public-dir /task --output /app/solution/mixed_fresh_validation.parquet --prepared-cache /app/solution/validation_cache.npz --checkpoint-dir /app/solution/mixed_fresh_ckpt --epochs 1 --threads 8"
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              "stdout": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nepoch=1/1 batches=250 targets=987,417 batch_bce=0.559269 running_bce=0.565164 elapsed=196.9s\nsaved epoch checkpoint: /app/solution/mixed_fresh_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.56307 validation_loss=0.51590 pair_accuracy=0.737 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.9 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=1 loss=0.515901\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_fresh_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 308.105,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5630657875696798,\n      \"positive_logit\": 0.5603278407790796,\n      \"negative_logit\": -0.5557115211259555,\n      \"pair_accuracy\": 0.7370967353243687,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 209.92406160300015,\n      \"validation_loss\": 0.5159006883799406,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.369371893999869\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.4622777700424194,\n    \"query_norm_std\": 0.669554591178894,\n    \"item_norm_mean\": 1.9108951091766357,\n    \"item_norm_std\": 0.794044017791748\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "stderr": "",
              "aggregated_output": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nepoch=1/1 batches=250 targets=987,417 batch_bce=0.559269 running_bce=0.565164 elapsed=196.9s\nsaved epoch checkpoint: /app/solution/mixed_fresh_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.56307 validation_loss=0.51590 pair_accuracy=0.737 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.9 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=1 loss=0.515901\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_fresh_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 308.105,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5630657875696798,\n      \"positive_logit\": 0.5603278407790796,\n      \"negative_logit\": -0.5557115211259555,\n      \"pair_accuracy\": 0.7370967353243687,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 209.92406160300015,\n      \"validation_loss\": 0.5159006883799406,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.369371893999869\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.4622777700424194,\n    \"query_norm_std\": 0.669554591178894,\n    \"item_norm_mean\": 1.9108951091766357,\n    \"item_norm_std\": 0.794044017791748\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
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              "formatted_output": "loaded full-sequence cache: tokens=20,056,329 targets=20,047,194\nchronological BCE window: train=1,052,953 validation=130,103 selected=1,183,056 discarded_old_targets=18,864,138 all=20,047,194\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.575 max=1.000\nfull-history false-negative filter: users=9,135 unique_user_items=5,524,275 bytes=34,256,250\nepoch=1/1 batches=250 targets=987,417 batch_bce=0.559269 running_bce=0.565164 elapsed=196.9s\nsaved epoch checkpoint: /app/solution/mixed_fresh_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.56307 validation_loss=0.51590 pair_accuracy=0.737 train_targets=1,052,953 validation_targets=130,103 train_seconds=209.9 validation_seconds=15.4\nrestored best validation-BCE checkpoint: epoch=1 loss=0.515901\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"validation\",\n  \"output\": \"/app/solution/mixed_fresh_validation.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 308.105,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 4,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20056329,\n  \"all_next_item_targets\": 20047194,\n  \"selected_training_targets\": 1052953,\n  \"selected_validation_targets\": 130103,\n  \"discarded_old_targets\": 18864138,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5630657875696798,\n      \"positive_logit\": 0.5603278407790796,\n      \"negative_logit\": -0.5557115211259555,\n      \"pair_accuracy\": 0.7370967353243687,\n      \"targets\": 1052953.0,\n      \"target_weight_sum\": 632551.0,\n      \"batches\": 266.0,\n      \"seconds\": 209.92406160300015,\n      \"validation_loss\": 0.5159006883799406,\n      \"validation_targets\": 130103.0,\n      \"validation_target_weight_sum\": 78769.25,\n      \"validation_seconds\": 15.369371893999869\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.4622777700424194,\n    \"query_norm_std\": 0.669554591178894,\n    \"item_norm_mean\": 1.9108951091766357,\n    \"item_norm_std\": 0.794044017791748\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n"
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          "input": {
            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python /task/evaluate_public.py /app/solution/mixed_fresh_validation.parquet\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:3000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:15:11.723Z",
            "content": "Script completed\nWall time 3.4 seconds\nOutput:\n\n{\n  \"model\": \"/app/solution/mixed_fresh_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.019452,\n    \"quality_users\": 4263\n  }\n}\n",
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              "status": "completed",
              "stdout": "{\n  \"model\": \"/app/solution/mixed_fresh_validation.parquet\",\n  \"scores\": {\n    \"quality_ndcg@10\": 0.019452,\n    \"quality_users\": 4263\n  }\n}\n",
              "stderr": "",
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          "text": ""
        },
        {
          "kind": "message",
          "timestamp": "2026-09-23T22:15:29.108Z",
          "text": "The controlled one-epoch hard-negative run scored 0.019452, so I’m rejecting that training change rather than shipping a plausible-sounding regression. The measured winner remains the original one-epoch training checkpoint plus indexable item-side calibration at 0.023345. I’m now making that calibration part of the production ranking implementation, restoring the proven negative mix as the default, and running the required final refit on `train + val`."
        },
        {
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          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n-    catalog_hard_negatives: int = 4\\n+    catalog_hard_negatives: int = 0\\n+    item_norm_power: float = 0.25\\n+    popularity_penalty: float = 0.15\\n@@\\n def rank_candidates(\\n@@\\n-    items = torch.cat(item_parts)\\n+    items = torch.cat(item_parts)\\n+    # Item-only calibration remains an indexed two-tower score. Algebraically\\n+    # this is an augmented dot product between [q, 1] and\\n+    # [v / ||v||**p, -lambda * standardized_log_popularity].\\n+    calibrated_items = items / torch.linalg.vector_norm(\\n+        items, dim=1, keepdim=True\\n+    ).clamp_min(1.0e-8).pow(config.item_norm_power)\\n+    popularity_bias = (\\n+        config.popularity_penalty\\n+        * torch.from_numpy(prepared.item_features[:, 0]).to(calibrated_items)\\n+    )\\n@@\\n-        scores = queries[start:end] @ items.T\\n+        scores = queries[start:end] @ calibrated_items.T\\n+        scores -= popularity_bias\\n@@\\n     parser.add_argument(\\n         \\\"--catalog-hard-negatives\\\",\\n@@\\n     )\\n+    parser.add_argument(\\n+        \\\"--item-norm-power\\\", type=float, default=Config.item_norm_power\\n+    )\\n+    parser.add_argument(\\n+        \\\"--popularity-penalty\\\", type=float, default=Config.popularity_penalty\\n+    )\\n@@\\n         or args.catalog_hard_negatives > Config.uniform_negatives\\n+        or args.item_norm_power < 0\\n+        or args.popularity_penalty < 0\\n@@\\n         catalog_hard_negatives=args.catalog_hard_negatives,\\n+        item_norm_power=args.item_norm_power,\\n+        popularity_penalty=args.popularity_penalty,\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:15:44.232Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n{}",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:15:44.155Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "FileChange",
              "id": "exec-c4542d9a-f68f-4280-9f11-0c679b4641c4",
              "changes": {
                "/app/solution/train_current_model.py": {
                  "type": "update",
                  "unified_diff": "@@ -61,3 +61,5 @@\n     catalog_negative_power: float = 0.75\n-    catalog_hard_negatives: int = 4\n+    catalog_hard_negatives: int = 0\n+    item_norm_power: float = 0.25\n+    popularity_penalty: float = 0.15\n     negative_filter_scope: str = \"full-training-history\"\n@@ -1904,2 +1906,12 @@\n     items = torch.cat(item_parts)\n+    # Item-only calibration remains an indexed two-tower score. Algebraically\n+    # this is an augmented dot product between [q, 1] and\n+    # [v / ||v||**p, -lambda * standardized_log_popularity].\n+    calibrated_items = items / torch.linalg.vector_norm(\n+        items, dim=1, keepdim=True\n+    ).clamp_min(1.0e-8).pow(config.item_norm_power)\n+    popularity_bias = (\n+        config.popularity_penalty\n+        * torch.from_numpy(prepared.item_features[:, 0]).to(calibrated_items)\n+    )\n     rows: list[tuple[int, int, int]] = []\n@@ -1907,3 +1919,4 @@\n         end = min(start + ranking_batch_size, len(eligibility.uids))\n-        scores = queries[start:end] @ items.T\n+        scores = queries[start:end] @ calibrated_items.T\n+        scores -= popularity_bias\n         eligible = np.unpackbits(\n@@ -1984,2 +1997,8 @@\n     parser.add_argument(\n+        \"--item-norm-power\", type=float, default=Config.item_norm_power\n+    )\n+    parser.add_argument(\n+        \"--popularity-penalty\", type=float, default=Config.popularity_penalty\n+    )\n+    parser.add_argument(\n         \"--target-weighting\",\n@@ -2057,2 +2076,4 @@\n         or args.catalog_hard_negatives > Config.uniform_negatives\n+        or args.item_norm_power < 0\n+        or args.popularity_penalty < 0\n         or args.max_train_targets_per_user < 0\n@@ -2075,2 +2096,4 @@\n         catalog_hard_negatives=args.catalog_hard_negatives,\n+        item_norm_power=args.item_norm_power,\n+        popularity_penalty=args.popularity_penalty,\n         target_weighting=args.target_weighting,\n",
                  "move_path": null
                }
              },
              "status": "completed",
              "stdout": "Success. Updated the following files:\nM /app/solution/train_current_model.py\n",
              "stderr": ""
            }
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            "timestamp": "2026-09-23T22:16:55.097Z",
            "content": "Script completed\nWall time 24.8 seconds\nOutput:\n\nprepared users=6,000 tokens=13,485,786 states=224,384 elapsed=31.7s\nprepared users=7,000 tokens=15,826,114 states=265,318 elapsed=37.5s\nprepared users=8,000 tokens=18,028,622 states=306,474 elapsed=43.1s\nprepared users=9,000 tokens=20,195,749 states=342,272 elapsed=48.1s\ntarget users without qualifying catalog sequence=6\nprepared stage=submission sequence_users=9,153 tokens=20,712,971 next_item_targets=20,703,818 states=350,322\nsaved public-derived full-sequence cache: /app/solution/submission_cache.npz\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nTraceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 2228, in <module>\n    raise SystemExit(main())\n                     ^^^^^^\n  File \"/app/solution/train_current_model.py\", line 2157, in main\n    model, training_history = train_model(\n                              ^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1717, in train_model\n    diagnostics = run_training_epoch(\n                  ^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1315, in run_training_epoch\n    negatives, negative_weights = draw_training_negatives(\n                                  ^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 761, in draw_training_negatives\n    return draw_full_history_filtered_negatives(\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 666, in draw_full_history_filtered_negatives\n    hard = torch.multinomial(\n           ^^^^^^^^^^^^^^^^^^\nRuntimeError: cannot sample n_sample <= 0 samples\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:16:30.378Z",
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        {
          "kind": "context",
          "timestamp": "2026-09-23T22:16:55.095Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-3bacc46d-9cac-4dcb-bfa2-07804f0fc109",
              "process_id": "15292",
              "command": [
                "/bin/sh",
                "-lc",
                "/opt/task-venv/bin/python -m py_compile /app/solution/train_current_model.py /app/solution/two_tower_model.py && /opt/task-venv/bin/python /app/solution/train_current_model.py --stage submission --public-dir /task --output /app/solution/submission.parquet --prepared-cache /app/solution/submission_cache.npz --checkpoint-dir /app/solution/final_ckpt --epochs 1 --threads 8"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python -m py_compile /app/solution/train_current_model.py /app/solution/two_tower_model.py && /opt/task-venv/bin/python /app/solution/train_current_model.py --stage submission --public-dir /task --output /app/solution/submission.parquet --prepared-cache /app/solution/submission_cache.npz --checkpoint-dir /app/solution/final_ckpt --epochs 1 --threads 8"
                }
              ],
              "source": "unified_exec_startup",
              "status": "failed",
              "stdout": "loaded explicit events: rows=746,504 users=8,307\nprepared users=1,000 tokens=2,167,338 states=37,073 elapsed=5.2s\nprepared users=2,000 tokens=4,450,246 states=73,784 elapsed=10.5s\nprepared users=3,000 tokens=6,703,970 states=113,190 elapsed=15.9s\nprepared users=4,000 tokens=9,087,187 states=153,283 elapsed=21.6s\nprepared users=5,000 tokens=11,354,844 states=188,776 elapsed=26.7s\nprepared users=6,000 tokens=13,485,786 states=224,384 elapsed=31.7s\nprepared users=7,000 tokens=15,826,114 states=265,318 elapsed=37.5s\nprepared users=8,000 tokens=18,028,622 states=306,474 elapsed=43.1s\nprepared users=9,000 tokens=20,195,749 states=342,272 elapsed=48.1s\ntarget users without qualifying catalog sequence=6\nprepared stage=submission sequence_users=9,153 tokens=20,712,971 next_item_targets=20,703,818 states=350,322\nsaved public-derived full-sequence cache: /app/solution/submission_cache.npz\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nTraceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 2228, in <module>\n    raise SystemExit(main())\n                     ^^^^^^\n  File \"/app/solution/train_current_model.py\", line 2157, in main\n    model, training_history = train_model(\n                              ^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1717, in train_model\n    diagnostics = run_training_epoch(\n                  ^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1315, in run_training_epoch\n    negatives, negative_weights = draw_training_negatives(\n                                  ^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 761, in draw_training_negatives\n    return draw_full_history_filtered_negatives(\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 666, in draw_full_history_filtered_negatives\n    hard = torch.multinomial(\n           ^^^^^^^^^^^^^^^^^^\nRuntimeError: cannot sample n_sample <= 0 samples\n",
              "stderr": "",
              "aggregated_output": "loaded explicit events: rows=746,504 users=8,307\nprepared users=1,000 tokens=2,167,338 states=37,073 elapsed=5.2s\nprepared users=2,000 tokens=4,450,246 states=73,784 elapsed=10.5s\nprepared users=3,000 tokens=6,703,970 states=113,190 elapsed=15.9s\nprepared users=4,000 tokens=9,087,187 states=153,283 elapsed=21.6s\nprepared users=5,000 tokens=11,354,844 states=188,776 elapsed=26.7s\nprepared users=6,000 tokens=13,485,786 states=224,384 elapsed=31.7s\nprepared users=7,000 tokens=15,826,114 states=265,318 elapsed=37.5s\nprepared users=8,000 tokens=18,028,622 states=306,474 elapsed=43.1s\nprepared users=9,000 tokens=20,195,749 states=342,272 elapsed=48.1s\ntarget users without qualifying catalog sequence=6\nprepared stage=submission sequence_users=9,153 tokens=20,712,971 next_item_targets=20,703,818 states=350,322\nsaved public-derived full-sequence cache: /app/solution/submission_cache.npz\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nTraceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 2228, in <module>\n    raise SystemExit(main())\n                     ^^^^^^\n  File \"/app/solution/train_current_model.py\", line 2157, in main\n    model, training_history = train_model(\n                              ^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1717, in train_model\n    diagnostics = run_training_epoch(\n                  ^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1315, in run_training_epoch\n    negatives, negative_weights = draw_training_negatives(\n                                  ^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 761, in draw_training_negatives\n    return draw_full_history_filtered_negatives(\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 666, in draw_full_history_filtered_negatives\n    hard = torch.multinomial(\n           ^^^^^^^^^^^^^^^^^^\nRuntimeError: cannot sample n_sample <= 0 samples\n",
              "exit_code": 1,
              "duration": {
                "secs": 61,
                "nanos": 354181145
              },
              "formatted_output": "loaded explicit events: rows=746,504 users=8,307\nprepared users=1,000 tokens=2,167,338 states=37,073 elapsed=5.2s\nprepared users=2,000 tokens=4,450,246 states=73,784 elapsed=10.5s\nprepared users=3,000 tokens=6,703,970 states=113,190 elapsed=15.9s\nprepared users=4,000 tokens=9,087,187 states=153,283 elapsed=21.6s\nprepared users=5,000 tokens=11,354,844 states=188,776 elapsed=26.7s\nprepared users=6,000 tokens=13,485,786 states=224,384 elapsed=31.7s\nprepared users=7,000 tokens=15,826,114 states=265,318 elapsed=37.5s\nprepared users=8,000 tokens=18,028,622 states=306,474 elapsed=43.1s\nprepared users=9,000 tokens=20,195,749 states=342,272 elapsed=48.1s\ntarget users without qualifying catalog sequence=6\nprepared stage=submission sequence_users=9,153 tokens=20,712,971 next_item_targets=20,703,818 states=350,322\nsaved public-derived full-sequence cache: /app/solution/submission_cache.npz\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nTraceback (most recent call last):\n  File \"/app/solution/train_current_model.py\", line 2228, in <module>\n    raise SystemExit(main())\n                     ^^^^^^\n  File \"/app/solution/train_current_model.py\", line 2157, in main\n    model, training_history = train_model(\n                              ^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1717, in train_model\n    diagnostics = run_training_epoch(\n                  ^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 1315, in run_training_epoch\n    negatives, negative_weights = draw_training_negatives(\n                                  ^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 761, in draw_training_negatives\n    return draw_full_history_filtered_negatives(\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/solution/train_current_model.py\", line 666, in draw_full_history_filtered_negatives\n    hard = torch.multinomial(\n           ^^^^^^^^^^^^^^^^^^\nRuntimeError: cannot sample n_sample <= 0 samples\n"
            }
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    },
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      "timestamp": "2026-09-23T22:16:57.132Z",
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          "callId": "call_NqyEOK45nwROHErREdH5aK1r",
          "name": "exec",
          "input": {
            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n-    hard = torch.multinomial(\\n-        proposal,\\n-        batch_size * hard_count,\\n-        replacement=True,\\n-        generator=generator,\\n-    ).reshape(batch_size, hard_count)\\n+    hard = (\\n+        torch.multinomial(\\n+            proposal,\\n+            batch_size * hard_count,\\n+            replacement=True,\\n+            generator=generator,\\n+        ).reshape(batch_size, hard_count)\\n+        if hard_count\\n+        else torch.empty((batch_size, 0), dtype=torch.long)\\n+    )\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:17:02.858Z",
            "content": "Script completed\nWall time 0.0 seconds\nOutput:\n\n{}",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:17:02.510Z",
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              "changes": {
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                  "type": "update",
                  "unified_diff": "@@ -665,8 +665,12 @@\n     )\n-    hard = torch.multinomial(\n-        proposal,\n-        batch_size * hard_count,\n-        replacement=True,\n-        generator=generator,\n-    ).reshape(batch_size, hard_count)\n+    hard = (\n+        torch.multinomial(\n+            proposal,\n+            batch_size * hard_count,\n+            replacement=True,\n+            generator=generator,\n+        ).reshape(batch_size, hard_count)\n+        if hard_count\n+        else torch.empty((batch_size, 0), dtype=torch.long)\n+    )\n     uniform = torch.cat([broad, hard], dim=1)\n",
                  "move_path": null
                }
              },
              "status": "completed",
              "stdout": "Success. Updated the following files:\nM /app/solution/train_current_model.py\n",
              "stderr": ""
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          "text": "The final data preparation completed, but the zero-hard-negative compatibility path exposed a PyTorch edge case (`multinomial(..., 0)` is invalid). I’ve fixed that branch; no data or model logic changed, and the cached final-stage sequences let the refit resume immediately without repeating preparation."
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          },
          "result": {
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            "content": "Script completed\nWall time 1.2 seconds\nOutput:\n\n{\"chunk_id\":\"cdac30\",\"wall_time_seconds\":1.000777822,\"session_id\":23549,\"original_token_count\":0,\"output\":\"\"}",
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              "stdout": "loaded full-sequence cache: tokens=20,712,971 targets=20,703,818\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nepoch=1/1 batches=250 targets=994,228 batch_bce=0.460538 running_bce=0.541708 elapsed=196.1s\nsaved epoch checkpoint: /app/solution/final_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.53835 validation_loss=0.49795 pair_accuracy=0.755 train_targets=1,067,606 validation_targets=131,997 train_seconds=211.0 validation_seconds=15.5\nrestored best validation-BCE checkpoint: epoch=1 loss=0.497949\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"submission\",\n  \"output\": \"/app/solution/submission.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 312.061,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 0,\n    \"item_norm_power\": 0.25,\n    \"popularity_penalty\": 0.15,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20712971,\n  \"all_next_item_targets\": 20703818,\n  \"selected_training_targets\": 1067606,\n  \"selected_validation_targets\": 131997,\n  \"discarded_old_targets\": 19504215,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5383531213538583,\n      \"positive_logit\": 0.7500169960101568,\n      \"negative_logit\": -0.630098677270996,\n      \"pair_accuracy\": 0.7552423073212402,\n      \"targets\": 1067606.0,\n      \"target_weight_sum\": 641383.25,\n      \"batches\": 270.0,\n      \"seconds\": 210.95327796699985,\n      \"validation_loss\": 0.4979486915141155,\n      \"validation_targets\": 131997.0,\n      \"validation_target_weight_sum\": 80328.75,\n      \"validation_seconds\": 15.479684333000023\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.651851773262024,\n    \"query_norm_std\": 0.8145269751548767,\n    \"item_norm_mean\": 1.9033515453338623,\n    \"item_norm_std\": 0.9598209261894226\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
              "stderr": "",
              "aggregated_output": "loaded full-sequence cache: tokens=20,712,971 targets=20,703,818\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nepoch=1/1 batches=250 targets=994,228 batch_bce=0.460538 running_bce=0.541708 elapsed=196.1s\nsaved epoch checkpoint: /app/solution/final_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.53835 validation_loss=0.49795 pair_accuracy=0.755 train_targets=1,067,606 validation_targets=131,997 train_seconds=211.0 validation_seconds=15.5\nrestored best validation-BCE checkpoint: epoch=1 loss=0.497949\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"submission\",\n  \"output\": \"/app/solution/submission.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 312.061,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 0,\n    \"item_norm_power\": 0.25,\n    \"popularity_penalty\": 0.15,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20712971,\n  \"all_next_item_targets\": 20703818,\n  \"selected_training_targets\": 1067606,\n  \"selected_validation_targets\": 131997,\n  \"discarded_old_targets\": 19504215,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5383531213538583,\n      \"positive_logit\": 0.7500169960101568,\n      \"negative_logit\": -0.630098677270996,\n      \"pair_accuracy\": 0.7552423073212402,\n      \"targets\": 1067606.0,\n      \"target_weight_sum\": 641383.25,\n      \"batches\": 270.0,\n      \"seconds\": 210.95327796699985,\n      \"validation_loss\": 0.4979486915141155,\n      \"validation_targets\": 131997.0,\n      \"validation_target_weight_sum\": 80328.75,\n      \"validation_seconds\": 15.479684333000023\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.651851773262024,\n    \"query_norm_std\": 0.8145269751548767,\n    \"item_norm_mean\": 1.9033515453338623,\n    \"item_norm_std\": 0.9598209261894226\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n",
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              "formatted_output": "loaded full-sequence cache: tokens=20,712,971 targets=20,703,818\nchronological BCE window: train=1,067,606 validation=131,997 selected=1,199,603 discarded_old_targets=19,504,215 all=20,703,818\ninbatch correction: min=0.250 mean_on_targets=1.001 max=4.000\ntarget weighting=organic-strong min=0.250 mean=0.576 max=1.000\nfull-history false-negative filter: users=9,153 unique_user_items=5,682,910 bytes=34,323,750\nepoch=1/1 batches=250 targets=994,228 batch_bce=0.460538 running_bce=0.541708 elapsed=196.1s\nsaved epoch checkpoint: /app/solution/final_ckpt/epoch-01.pt\nepoch=1/1 train_loss=0.53835 validation_loss=0.49795 pair_accuracy=0.755 train_targets=1,067,606 validation_targets=131,997 train_seconds=211.0 validation_seconds=15.5\nrestored best validation-BCE checkpoint: epoch=1 loss=0.497949\nranked users=1,024/8,456\nranked users=2,048/8,456\nranked users=3,072/8,456\nranked users=4,096/8,456\nranked users=5,120/8,456\nranked users=6,144/8,456\nranked users=7,168/8,456\nranked users=8,192/8,456\nranked users=8,456/8,456\n{\n  \"baseline\": \"yambda-windowed-sequence-two-tower-base\",\n  \"stage\": \"submission\",\n  \"output\": \"/app/solution/submission.parquet\",\n  \"rows\": 845600,\n  \"users\": 8456,\n  \"runtime_seconds\": 312.061,\n  \"public_inputs_only\": true,\n  \"architecture\": {\n    \"family\": \"pure-windowed-sequence-two-tower\",\n    \"sequence_training\": \"every-adjacent-target-within-recent-chronological-window\",\n    \"sequence_encoder\": \"one-layer-GRU-dense-timestep-loss\",\n    \"bptt_hidden_state\": \"carried-and-detached\",\n    \"model_selection\": \"chronological-validation-BCE-early-stopping\",\n    \"loss_execution\": \"gradient-accumulated-microbatches\",\n    \"user_id_embedding\": false,\n    \"user_mlp\": \"582-512-256-192\",\n    \"item_mlp\": \"196-512-256-192\",\n    \"normalization\": \"none\",\n    \"score\": \"raw-dot-product\",\n    \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n    \"negative_sampling\": \"24-uniform-plus-8-propensity-corrected-inbatch\",\n    \"false_negative_filter\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\"\n  },\n  \"config\": {\n    \"bptt_steps\": 100,\n    \"user_batch_size\": 64,\n    \"embedding_dim\": 192,\n    \"hidden_dim\": 192,\n    \"user_hidden_1\": 512,\n    \"user_hidden_2\": 256,\n    \"item_hidden_1\": 512,\n    \"item_hidden_2\": 256,\n    \"dropout\": 0.05,\n    \"epochs\": 1,\n    \"learning_rate\": 0.001,\n    \"weight_decay\": 1e-05,\n    \"gradient_clip\": 2.0,\n    \"loss_microbatch_size\": 65536,\n    \"uniform_negatives\": 24,\n    \"inbatch_negatives\": 8,\n    \"inbatch_correction_power\": 0.5,\n    \"inbatch_correction_min\": 0.25,\n    \"inbatch_correction_max\": 4.0,\n    \"catalog_negative_power\": 0.75,\n    \"catalog_hard_negatives\": 0,\n    \"item_norm_power\": 0.25,\n    \"popularity_penalty\": 0.15,\n    \"negative_filter_scope\": \"full-training-history\",\n    \"target_weighting\": \"organic-strong\",\n    \"ordinary_target_weight\": 0.25,\n    \"organic_strong_target_weight\": 1.0,\n    \"organic_like_target_weight\": 3.0,\n    \"discovery_horizon_days\": 7,\n    \"validation_fraction\": 0.1,\n    \"max_train_targets_per_user\": 128,\n    \"max_validation_targets_per_user\": 16,\n    \"early_stopping_patience\": 1,\n    \"early_stopping_min_delta\": 0.0001,\n    \"seed\": 29\n  },\n  \"sequence_tokens\": 20712971,\n  \"all_next_item_targets\": 20703818,\n  \"selected_training_targets\": 1067606,\n  \"selected_validation_targets\": 131997,\n  \"discarded_old_targets\": 19504215,\n  \"training_history\": [\n    {\n      \"epoch\": 1.0,\n      \"loss\": 0.5383531213538583,\n      \"positive_logit\": 0.7500169960101568,\n      \"negative_logit\": -0.630098677270996,\n      \"pair_accuracy\": 0.7552423073212402,\n      \"targets\": 1067606.0,\n      \"target_weight_sum\": 641383.25,\n      \"batches\": 270.0,\n      \"seconds\": 210.95327796699985,\n      \"validation_loss\": 0.4979486915141155,\n      \"validation_targets\": 131997.0,\n      \"validation_target_weight_sum\": 80328.75,\n      \"validation_seconds\": 15.479684333000023\n    }\n  ],\n  \"embedding_diagnostics\": {\n    \"query_norm_mean\": 1.651851773262024,\n    \"query_norm_std\": 0.8145269751548767,\n    \"item_norm_mean\": 1.9033515453338623,\n    \"item_norm_std\": 0.9598209261894226\n  },\n  \"torch_version\": \"2.8.0+cpu\",\n  \"device\": \"cpu\"\n}\n"
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          "text": "The final refit completed on `train + val` and wrote 845,600 rows for all 8,456 target users. I’m doing the last gate now: exact users, 100 distinct eligible items per user, ranks 1–100, integer/finite columns, and a regular (non-symlink) Parquet file. I’m also recording the rejected negative-sampling experiments and the measured calibration gain in the README so the experiment trail is honest and reproducible."
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            "code": "const patch = \"*** Begin Patch\\n*** Add File: /app/solution/README.md\\n+# Improved production two-tower\\n+\\n+## Result\\n+\\n+- Reproduced production public NDCG@10: **0.021280** (4,263 scored users).\\n+- Selected model public NDCG@10: **0.023345** (4,263 scored users), a **9.7% relative gain**.\\n+- Final `submission.parquet` is refit with `train_* + val_*` history and ranked only over the supplied test candidates.\\n+\\n+## Diagnosis and experiments\\n+\\n+The baseline samples 24 catalog-uniform negatives and eight corrected in-batch\\n+negatives. Its sampled validation BCE looks good, but most uniform draws are\\n+easy tail items and do not constrain the item norm/popularity effects that\\n+dominate the top of the index. Public diagnostics confirmed that adding more\\n+popularity prior reduced NDCG, while modestly controlling it improved NDCG.\\n+\\n+The implementation adds an optional, full-history-filtered tempered-popularity\\n+negative proposal (`--catalog-hard-negatives` and\\n+`--catalog-negative-power`). Controlled public tests rejected enabling it in\\n+the shipped recipe: four hard negatives scored 0.019452 from scratch, and an\\n+aggressive proposal scored 0.014692 after fine-tuning. These results showed\\n+that biased hard-negative training over-corrected under the one-epoch CPU\\n+budget, so the final default conservatively retains the proven negative mix.\\n+\\n+The selected change is item-side score calibration: precomputed item vectors\\n+are divided by `norm**0.25`, and a `0.15 * standardized_log_popularity` item\\n+bias is subtracted. This is still an indexable two-tower dot product by\\n+augmenting the query with a constant coordinate and each precomputed item\\n+vector with its bias. It adds no per-candidate sequence computation, user-ID\\n+lookup, or cross-encoder.\\n+\\n+## Reproduce final artifact\\n+\\n+```sh\\n+/opt/task-venv/bin/python /app/solution/train_current_model.py \\\\\\n+  --stage submission \\\\\\n+  --public-dir /task \\\\\\n+  --output /app/solution/submission.parquet \\\\\\n+  --prepared-cache /app/solution/submission_cache.npz \\\\\\n+  --checkpoint-dir /app/solution/final_ckpt \\\\\\n+  --epochs 1 --threads 8\\n+```\\n+\\n+The public validation calibration selected `--item-norm-power 0.25` and\\n+`--popularity-penalty 0.15`; both are defaults in the submitted script.\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
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            "timestamp": "2026-09-23T22:23:03.035Z",
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                "/app/solution/README.md": {
                  "type": "add",
                  "content": "# Improved production two-tower\n\n## Result\n\n- Reproduced production public NDCG@10: **0.021280** (4,263 scored users).\n- Selected model public NDCG@10: **0.023345** (4,263 scored users), a **9.7% relative gain**.\n- Final `submission.parquet` is refit with `train_* + val_*` history and ranked only over the supplied test candidates.\n\n## Diagnosis and experiments\n\nThe baseline samples 24 catalog-uniform negatives and eight corrected in-batch\nnegatives. Its sampled validation BCE looks good, but most uniform draws are\neasy tail items and do not constrain the item norm/popularity effects that\ndominate the top of the index. Public diagnostics confirmed that adding more\npopularity prior reduced NDCG, while modestly controlling it improved NDCG.\n\nThe implementation adds an optional, full-history-filtered tempered-popularity\nnegative proposal (`--catalog-hard-negatives` and\n`--catalog-negative-power`). Controlled public tests rejected enabling it in\nthe shipped recipe: four hard negatives scored 0.019452 from scratch, and an\naggressive proposal scored 0.014692 after fine-tuning. These results showed\nthat biased hard-negative training over-corrected under the one-epoch CPU\nbudget, so the final default conservatively retains the proven negative mix.\n\nThe selected change is item-side score calibration: precomputed item vectors\nare divided by `norm**0.25`, and a `0.15 * standardized_log_popularity` item\nbias is subtracted. This is still an indexable two-tower dot product by\naugmenting the query with a constant coordinate and each precomputed item\nvector with its bias. It adds no per-candidate sequence computation, user-ID\nlookup, or cross-encoder.\n\n## Reproduce final artifact\n\n```sh\n/opt/task-venv/bin/python /app/solution/train_current_model.py \\\n  --stage submission \\\n  --public-dir /task \\\n  --output /app/solution/submission.parquet \\\n  --prepared-cache /app/solution/submission_cache.npz \\\n  --checkpoint-dir /app/solution/final_ckpt \\\n  --epochs 1 --threads 8\n```\n\nThe public validation calibration selected `--item-norm-power 0.25` and\n`--popularity-penalty 0.15`; both are defaults in the submitted script.\n"
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              "status": "completed",
              "stdout": "Success. Updated the following files:\nA /app/solution/README.md\n",
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            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python - <<'PY'\\nfrom pathlib import Path\\nimport numpy as np, pandas as pd\\nout=Path('/app/solution/submission.parquet')\\nassert out.is_file() and not out.is_symlink()\\nr=pd.read_parquet(out,columns=['uid','item_id','rank'])\\ntarget=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64)\\nz=np.load('/task/data/test_eligible_candidates.npz')\\nassert list(r.columns)==['uid','item_id','rank']\\nassert len(r)==len(target)*100\\nassert all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns)\\nassert np.isfinite(r.to_numpy()).all()\\nassert set(r.uid)==set(target)==set(z['uids'])\\ng=r.groupby('uid',sort=False)\\nassert (g.size()==100).all()\\nassert (g.item_id.nunique()==100).all()\\nassert all(np.array_equal(np.sort(x),np.arange(1,101)) for x in g['rank'])\\nitem_to_col={int(x):i for i,x in enumerate(z['item_ids'])}\\nuid_to_row={int(x):i for i,x in enumerate(z['uids'])}\\nfor uid,items in g.item_id:\\n    mask=np.unpackbits(z['packed_eligible'][uid_to_row[int(uid)]],count=len(z['item_ids']),bitorder='little')\\n    assert all(mask[item_to_col[int(item)]] for item in items)\\nprint({'path':str(out),'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(g.size().min()),int(g.size().max())],'distinct_items_per_user':[int(g.item_id.nunique().min()),int(g.item_id.nunique().max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':True,'dtypes':{c:str(r[c].dtype) for c in r.columns}})\\nPY\\nls -lh /app/solution/submission.parquet /app/solution/train_current_model.py /app/solution/two_tower_model.py /app/solution/README.md\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:5000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:23:23.424Z",
            "content": "Script completed\nWall time 1.7 seconds\nOutput:\n\nTraceback (most recent call last):\n  File \"<stdin>\", line 16, in <module>\n  File \"<stdin>\", line 16, in <genexpr>\n  File \"/opt/task-venv/lib/python3.12/site-packages/numpy/_core/fromnumeric.py\", line 1121, in sort\n    a = asanyarray(a).copy(order=\"K\")\n        ^^^^^^^^^^^^^\nValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 1 dimensions. The detected shape was (2,) + inhomogeneous part.\n-rw-r--r-- 1 agent agent 2.1K Sep 23 22:23 /app/solution/README.md\n-rw-r--r-- 1 agent agent 1.2M Sep 23 22:22 /app/solution/submission.parquet\n-rw-r--r-- 1 agent agent  82K Sep 23 22:17 /app/solution/train_current_model.py\n-rw-r--r-- 1 agent agent  16K Sep 23 21:39 /app/solution/two_tower_model.py\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:23:21.848Z",
          "data": {
            "type": "token_usage_record",
            "thread_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "session_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
            "response_id": "resp_038c43f9aa686cae016ab451474aa087d29d26e535fcb119f0",
            "usage": {
              "input_tokens": 73930,
              "cached_input_tokens": 72704,
              "cache_write_input_tokens": 0,
              "output_tokens": 542,
              "reasoning_output_tokens": 15,
              "total_tokens": 74472
            },
            "turn_token_usage": {
              "input_tokens": 5804776,
              "cached_input_tokens": 5723904,
              "cache_write_input_tokens": 0,
              "output_tokens": 17968,
              "reasoning_output_tokens": 5394,
              "total_tokens": 5822744
            },
            "thread_token_usage": {
              "input_tokens": 5804776,
              "cached_input_tokens": 5723904,
              "cache_write_input_tokens": 0,
              "output_tokens": 17968,
              "reasoning_output_tokens": 5394,
              "total_tokens": 5822744
            }
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:23:23.420Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-12e91305-c2f3-47f1-aa2f-fb5359c64ab4",
              "process_id": "53865",
              "command": [
                "/bin/sh",
                "-lc",
                "/opt/task-venv/bin/python - <<'PY'\nfrom pathlib import Path\nimport numpy as np, pandas as pd\nout=Path('/app/solution/submission.parquet')\nassert out.is_file() and not out.is_symlink()\nr=pd.read_parquet(out,columns=['uid','item_id','rank'])\ntarget=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64)\nz=np.load('/task/data/test_eligible_candidates.npz')\nassert list(r.columns)==['uid','item_id','rank']\nassert len(r)==len(target)*100\nassert all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns)\nassert np.isfinite(r.to_numpy()).all()\nassert set(r.uid)==set(target)==set(z['uids'])\ng=r.groupby('uid',sort=False)\nassert (g.size()==100).all()\nassert (g.item_id.nunique()==100).all()\nassert all(np.array_equal(np.sort(x),np.arange(1,101)) for x in g['rank'])\nitem_to_col={int(x):i for i,x in enumerate(z['item_ids'])}\nuid_to_row={int(x):i for i,x in enumerate(z['uids'])}\nfor uid,items in g.item_id:\n    mask=np.unpackbits(z['packed_eligible'][uid_to_row[int(uid)]],count=len(z['item_ids']),bitorder='little')\n    assert all(mask[item_to_col[int(item)]] for item in items)\nprint({'path':str(out),'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(g.size().min()),int(g.size().max())],'distinct_items_per_user':[int(g.item_id.nunique().min()),int(g.item_id.nunique().max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':True,'dtypes':{c:str(r[c].dtype) for c in r.columns}})\nPY\nls -lh /app/solution/submission.parquet /app/solution/train_current_model.py /app/solution/two_tower_model.py /app/solution/README.md"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python - <<'PY'\nfrom pathlib import Path\nimport numpy as np, pandas as pd\nout=Path('/app/solution/submission.parquet')\nassert out.is_file() and not out.is_symlink()\nr=pd.read_parquet(out,columns=['uid','item_id','rank'])\ntarget=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64)\nz=np.load('/task/data/test_eligible_candidates.npz')\nassert list(r.columns)==['uid','item_id','rank']\nassert len(r)==len(target)*100\nassert all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns)\nassert np.isfinite(r.to_numpy()).all()\nassert set(r.uid)==set(target)==set(z['uids'])\ng=r.groupby('uid',sort=False)\nassert (g.size()==100).all()\nassert (g.item_id.nunique()==100).all()\nassert all(np.array_equal(np.sort(x),np.arange(1,101)) for x in g['rank'])\nitem_to_col={int(x):i for i,x in enumerate(z['item_ids'])}\nuid_to_row={int(x):i for i,x in enumerate(z['uids'])}\nfor uid,items in g.item_id:\n    mask=np.unpackbits(z['packed_eligible'][uid_to_row[int(uid)]],count=len(z['item_ids']),bitorder='little')\n    assert all(mask[item_to_col[int(item)]] for item in items)\nprint({'path':str(out),'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(g.size().min()),int(g.size().max())],'distinct_items_per_user':[int(g.item_id.nunique().min()),int(g.item_id.nunique().max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':True,'dtypes':{c:str(r[c].dtype) for c in r.columns}})\nPY\nls -lh /app/solution/submission.parquet /app/solution/train_current_model.py /app/solution/two_tower_model.py /app/solution/README.md"
                }
              ],
              "source": "unified_exec_startup",
              "status": "completed",
              "stdout": "Traceback (most recent call last):\n  File \"<stdin>\", line 16, in <module>\n  File \"<stdin>\", line 16, in <genexpr>\n  File \"/opt/task-venv/lib/python3.12/site-packages/numpy/_core/fromnumeric.py\", line 1121, in sort\n    a = asanyarray(a).copy(order=\"K\")\n        ^^^^^^^^^^^^^\nValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 1 dimensions. The detected shape was (2,) + inhomogeneous part.\n-rw-r--r-- 1 agent agent 2.1K Sep 23 22:23 /app/solution/README.md\n-rw-r--r-- 1 agent agent 1.2M Sep 23 22:22 /app/solution/submission.parquet\n-rw-r--r-- 1 agent agent  82K Sep 23 22:17 /app/solution/train_current_model.py\n-rw-r--r-- 1 agent agent  16K Sep 23 21:39 /app/solution/two_tower_model.py\n",
              "stderr": "",
              "aggregated_output": "Traceback (most recent call last):\n  File \"<stdin>\", line 16, in <module>\n  File \"<stdin>\", line 16, in <genexpr>\n  File \"/opt/task-venv/lib/python3.12/site-packages/numpy/_core/fromnumeric.py\", line 1121, in sort\n    a = asanyarray(a).copy(order=\"K\")\n        ^^^^^^^^^^^^^\nValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 1 dimensions. The detected shape was (2,) + inhomogeneous part.\n-rw-r--r-- 1 agent agent 2.1K Sep 23 22:23 /app/solution/README.md\n-rw-r--r-- 1 agent agent 1.2M Sep 23 22:22 /app/solution/submission.parquet\n-rw-r--r-- 1 agent agent  82K Sep 23 22:17 /app/solution/train_current_model.py\n-rw-r--r-- 1 agent agent  16K Sep 23 21:39 /app/solution/two_tower_model.py\n",
              "exit_code": 0,
              "duration": {
                "secs": 1,
                "nanos": 552924188
              },
              "formatted_output": "Traceback (most recent call last):\n  File \"<stdin>\", line 16, in <module>\n  File \"<stdin>\", line 16, in <genexpr>\n  File \"/opt/task-venv/lib/python3.12/site-packages/numpy/_core/fromnumeric.py\", line 1121, in sort\n    a = asanyarray(a).copy(order=\"K\")\n        ^^^^^^^^^^^^^\nValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 1 dimensions. The detected shape was (2,) + inhomogeneous part.\n-rw-r--r-- 1 agent agent 2.1K Sep 23 22:23 /app/solution/README.md\n-rw-r--r-- 1 agent agent 1.2M Sep 23 22:22 /app/solution/submission.parquet\n-rw-r--r-- 1 agent agent  82K Sep 23 22:17 /app/solution/train_current_model.py\n-rw-r--r-- 1 agent agent  16K Sep 23 21:39 /app/solution/two_tower_model.py\n"
            }
          }
        }
      ]
    },
    {
      "id": 79,
      "role": "agent",
      "timestamp": "2026-09-23T22:23:26.774Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T22:23:26.774Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T22:23:41.306Z",
          "callId": "call_QX4dts1PGQIp5OEfmfhZuVsV",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python - <<'PY'\\nfrom pathlib import Path\\nimport numpy as np, pandas as pd\\nout=Path('/app/solution/submission.parquet'); assert out.is_file() and not out.is_symlink()\\nr=pd.read_parquet(out,columns=['uid','item_id','rank']); target=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64); z=np.load('/task/data/test_eligible_candidates.npz')\\nassert len(r)==len(target)*100 and all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns) and np.isfinite(r.to_numpy()).all()\\nassert set(r.uid)==set(target)==set(z['uids']); g=r.groupby('uid',sort=False)\\nassert (g.size()==100).all() and (g.item_id.nunique()==100).all()\\nassert all(np.array_equal(np.sort(s.to_numpy()),np.arange(1,101)) for _,s in g['rank'])\\nitem_to_col={int(x):i for i,x in enumerate(z['item_ids'])}; uid_to_row={int(x):i for i,x in enumerate(z['uids'])}\\nfor uid,s in g['item_id']:\\n mask=np.unpackbits(z['packed_eligible'][uid_to_row[int(uid)]],count=len(z['item_ids']),bitorder='little')\\n assert all(mask[item_to_col[int(item)]] for item in s)\\nprint({'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(g.size().min()),int(g.size().max())],'distinct_items_per_user':[int(g.item_id.nunique().min()),int(g.item_id.nunique().max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':True,'dtypes':{c:str(r[c].dtype) for c in r.columns}})\\nPY\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:3000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:24:11.476Z",
            "content": "Script completed\nWall time 30.2 seconds\nOutput:\n\n",
            "isError": null
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:23:41.419Z",
          "data": {
            "type": "token_usage_record",
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            "session_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
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              "cache_write_input_tokens": 0,
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            "turn_token_usage": {
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            "thread_token_usage": {
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              "reasoning_output_tokens": 5437,
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        }
      ]
    },
    {
      "id": 80,
      "role": "agent",
      "timestamp": "2026-09-23T22:24:18.603Z",
      "blocks": [
        {
          "kind": "reasoning",
          "representation": "summary",
          "timestamp": "2026-09-23T22:24:18.603Z",
          "text": ""
        },
        {
          "kind": "tool",
          "timestamp": "2026-09-23T22:24:32.657Z",
          "callId": "call_JT959XBi4QPLRlpnV8DNHzTC",
          "name": "exec",
          "input": {
            "code": "const r = await tools.exec_command({cmd:\"/opt/task-venv/bin/python - <<'PY'\\nfrom pathlib import Path\\nimport numpy as np, pandas as pd\\nout=Path('/app/solution/submission.parquet'); assert out.is_file() and not out.is_symlink()\\nr=pd.read_parquet(out,columns=['uid','item_id','rank']); target=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64); z=np.load('/task/data/test_eligible_candidates.npz')\\nassert len(r)==len(target)*100 and all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns) and np.isfinite(r.to_numpy()).all(); assert set(r.uid)==set(target)==set(z['uids'])\\ng=r.groupby('uid',sort=False); sizes=g.size(); distinct=g.item_id.nunique(); assert (sizes==100).all() and (distinct==100).all()\\nranks=np.sort(r['rank'].to_numpy().reshape(len(target),100),axis=1); assert np.all(ranks==np.arange(1,101))\\nrows=pd.Index(z['uids']).get_indexer(r.uid); cols=pd.Index(z['item_ids']).get_indexer(r.item_id); assert (rows>=0).all() and (cols>=0).all(); packed=z['packed_eligible']; ok=((packed[rows,cols>>3]>>(cols&7))&1).astype(bool); assert ok.all()\\nprint({'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(sizes.min()),int(sizes.max())],'distinct_items_per_user':[int(distinct.min()),int(distinct.max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':bool(ok.all()),'dtypes':{c:str(r[c].dtype) for c in r.columns}})\\nPY\",workdir:\"/app\",yield_time_ms:30000,max_output_tokens:3000}); text(r.output)\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:24:34.549Z",
            "content": "Script completed\nWall time 1.9 seconds\nOutput:\n\n{'regular_file': True, 'rows': 845600, 'users': 8456, 'rows_per_user': [100, 100], 'distinct_items_per_user': [100, 100], 'rank_range': [1, 100], 'all_test_eligible': True, 'dtypes': {'uid': 'int64', 'item_id': 'int64', 'rank': 'int64'}}\n",
            "isError": null
          }
        },
        {
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          "timestamp": "2026-09-23T22:24:32.787Z",
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            "session_id": "01a0d035-d127-7532-9187-ef65c3f614a5",
            "root_turn_id": "01a0d035-d135-77c1-9bc8-81a39dc8028d",
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              "reasoning_output_tokens": 5584,
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            }
          }
        },
        {
          "kind": "context",
          "timestamp": "2026-09-23T22:24:34.545Z",
          "data": {
            "type": "codex_item_completed",
            "item": {
              "type": "CommandExecution",
              "id": "exec-18851d0c-ad4f-403c-a87e-d50054695e30",
              "process_id": "74574",
              "command": [
                "/bin/sh",
                "-lc",
                "/opt/task-venv/bin/python - <<'PY'\nfrom pathlib import Path\nimport numpy as np, pandas as pd\nout=Path('/app/solution/submission.parquet'); assert out.is_file() and not out.is_symlink()\nr=pd.read_parquet(out,columns=['uid','item_id','rank']); target=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64); z=np.load('/task/data/test_eligible_candidates.npz')\nassert len(r)==len(target)*100 and all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns) and np.isfinite(r.to_numpy()).all(); assert set(r.uid)==set(target)==set(z['uids'])\ng=r.groupby('uid',sort=False); sizes=g.size(); distinct=g.item_id.nunique(); assert (sizes==100).all() and (distinct==100).all()\nranks=np.sort(r['rank'].to_numpy().reshape(len(target),100),axis=1); assert np.all(ranks==np.arange(1,101))\nrows=pd.Index(z['uids']).get_indexer(r.uid); cols=pd.Index(z['item_ids']).get_indexer(r.item_id); assert (rows>=0).all() and (cols>=0).all(); packed=z['packed_eligible']; ok=((packed[rows,cols>>3]>>(cols&7))&1).astype(bool); assert ok.all()\nprint({'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(sizes.min()),int(sizes.max())],'distinct_items_per_user':[int(distinct.min()),int(distinct.max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':bool(ok.all()),'dtypes':{c:str(r[c].dtype) for c in r.columns}})\nPY"
              ],
              "cwd": "file:///app",
              "parsed_cmd": [
                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python - <<'PY'\nfrom pathlib import Path\nimport numpy as np, pandas as pd\nout=Path('/app/solution/submission.parquet'); assert out.is_file() and not out.is_symlink()\nr=pd.read_parquet(out,columns=['uid','item_id','rank']); target=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64); z=np.load('/task/data/test_eligible_candidates.npz')\nassert len(r)==len(target)*100 and all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns) and np.isfinite(r.to_numpy()).all(); assert set(r.uid)==set(target)==set(z['uids'])\ng=r.groupby('uid',sort=False); sizes=g.size(); distinct=g.item_id.nunique(); assert (sizes==100).all() and (distinct==100).all()\nranks=np.sort(r['rank'].to_numpy().reshape(len(target),100),axis=1); assert np.all(ranks==np.arange(1,101))\nrows=pd.Index(z['uids']).get_indexer(r.uid); cols=pd.Index(z['item_ids']).get_indexer(r.item_id); assert (rows>=0).all() and (cols>=0).all(); packed=z['packed_eligible']; ok=((packed[rows,cols>>3]>>(cols&7))&1).astype(bool); assert ok.all()\nprint({'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(sizes.min()),int(sizes.max())],'distinct_items_per_user':[int(distinct.min()),int(distinct.max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':bool(ok.all()),'dtypes':{c:str(r[c].dtype) for c in r.columns}})\nPY"
                }
              ],
              "source": "unified_exec_startup",
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              "stdout": "{'regular_file': True, 'rows': 845600, 'users': 8456, 'rows_per_user': [100, 100], 'distinct_items_per_user': [100, 100], 'rank_range': [1, 100], 'all_test_eligible': True, 'dtypes': {'uid': 'int64', 'item_id': 'int64', 'rank': 'int64'}}\n",
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            "code": "const patch = \"*** Begin Patch\\n*** Update File: /app/solution/train_current_model.py\\n@@\\n-The model is a pure two-tower retriever: no user-ID embedding, no output\\n-normalization, raw dot-product retrieval, sample-weighted binary cross entropy,\\n-and 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\\n-selected adjacent target retains a nonzero weight. Only files under the supplied\\n-public directory are read.\\n+The model is a pure two-tower retriever: no user-ID embedding, item-side norm\\n+and popularity calibration, sample-weighted binary cross entropy, and 24\\n+catalog plus eight propensity-corrected unique in-batch negatives. Optional\\n+tempered-popularity negatives support controlled hard-negative experiments.\\n+Every selected adjacent target retains a nonzero weight. Only files under the\\n+supplied public directory are read.\\n@@\\n-                    \\\"normalization\\\": \\\"none\\\",\\n-                    \\\"score\\\": \\\"raw-dot-product\\\",\\n+                    \\\"normalization\\\": (\\n+                        f\\\"item-norm-power-{config.item_norm_power}\\\"\\n+                    ),\\n+                    \\\"score\\\": (\\n+                        \\\"augmented-dot-product-with-item-popularity-bias-\\\"\\n+                        f\\\"{config.popularity_penalty}\\\"\\n+                    ),\\n@@\\n-                        \\\"24-uniform-plus-8-propensity-corrected-inbatch\\\"\\n+                        f\\\"{config.uniform_negatives - config.catalog_hard_negatives}-uniform-\\\"\\n+                        f\\\"plus-{config.catalog_hard_negatives}-tempered-popularity-\\\"\\n+                        f\\\"plus-{config.inbatch_negatives}-propensity-corrected-inbatch\\\"\\n*** End Patch\";\ntext(await tools.apply_patch(patch));\n"
          },
          "result": {
            "timestamp": "2026-09-23T22:24:53.793Z",
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                  "type": "update",
                  "unified_diff": "@@ -11,7 +11,8 @@\n \n-The model is a pure two-tower retriever: no user-ID embedding, no output\n-normalization, raw dot-product retrieval, sample-weighted binary cross entropy,\n-and 24 uniform plus eight propensity-corrected unique in-batch negatives. Every\n-selected adjacent target retains a nonzero weight. Only files under the supplied\n-public directory are read.\n+The model is a pure two-tower retriever: no user-ID embedding, item-side norm\n+and popularity calibration, sample-weighted binary cross entropy, and 24\n+catalog plus eight propensity-corrected unique in-batch negatives. Optional\n+tempered-popularity negatives support controlled hard-negative experiments.\n+Every selected adjacent target retains a nonzero weight. Only files under the\n+supplied public directory are read.\n \"\"\"\n@@ -2200,7 +2201,14 @@\n                     \"item_mlp\": \"196-512-256-192\",\n-                    \"normalization\": \"none\",\n-                    \"score\": \"raw-dot-product\",\n+                    \"normalization\": (\n+                        f\"item-norm-power-{config.item_norm_power}\"\n+                    ),\n+                    \"score\": (\n+                        \"augmented-dot-product-with-item-popularity-bias-\"\n+                        f\"{config.popularity_penalty}\"\n+                    ),\n                     \"objective\": \"sample-weighted-BCE-at-every-timestep\",\n                     \"negative_sampling\": (\n-                        \"24-uniform-plus-8-propensity-corrected-inbatch\"\n+                        f\"{config.uniform_negatives - config.catalog_hard_negatives}-uniform-\"\n+                        f\"plus-{config.catalog_hard_negatives}-tempered-popularity-\"\n+                        f\"plus-{config.inbatch_negatives}-propensity-corrected-inbatch\"\n                     ),\n",
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        {
          "kind": "message",
          "timestamp": "2026-09-23T22:25:09.790Z",
          "text": "Completed and validated the final ranking.\n\n- Submission: [submission.parquet](/app/solution/submission.parquet)\n- Improved trainer: [train_current_model.py](/app/solution/train_current_model.py)\n- Model primitives: [two_tower_model.py](/app/solution/two_tower_model.py)\n- Experiment record: [README.md](/app/solution/README.md)\n\nResults:\n\n- Production public NDCG@10: `0.021280`\n- Improved public NDCG@10: `0.023345`\n- Relative improvement: `9.7%`\n\nThe final artifact was refit on `train_* + val_*`. Validation confirmed exactly 8,456 users, 100 distinct eligible items per user, ranks 1–100, integer columns, and no test-ineligible items."
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                "-lc",
                "/opt/task-venv/bin/python - <<'PY'\nfrom pathlib import Path\nimport numpy as np, pandas as pd\nout=Path('/app/solution/submission.parquet'); assert out.is_file() and not out.is_symlink()\nr=pd.read_parquet(out,columns=['uid','item_id','rank']); target=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64); z=np.load('/task/data/test_eligible_candidates.npz')\nassert len(r)==len(target)*100 and all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns) and np.isfinite(r.to_numpy()).all()\nassert set(r.uid)==set(target)==set(z['uids']); g=r.groupby('uid',sort=False)\nassert (g.size()==100).all() and (g.item_id.nunique()==100).all()\nassert all(np.array_equal(np.sort(s.to_numpy()),np.arange(1,101)) for _,s in g['rank'])\nitem_to_col={int(x):i for i,x in enumerate(z['item_ids'])}; uid_to_row={int(x):i for i,x in enumerate(z['uids'])}\nfor uid,s in g['item_id']:\n mask=np.unpackbits(z['packed_eligible'][uid_to_row[int(uid)]],count=len(z['item_ids']),bitorder='little')\n assert all(mask[item_to_col[int(item)]] for item in s)\nprint({'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(g.size().min()),int(g.size().max())],'distinct_items_per_user':[int(g.item_id.nunique().min()),int(g.item_id.nunique().max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':True,'dtypes':{c:str(r[c].dtype) for c in r.columns}})\nPY"
              ],
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                {
                  "type": "unknown",
                  "cmd": "/opt/task-venv/bin/python - <<'PY'\nfrom pathlib import Path\nimport numpy as np, pandas as pd\nout=Path('/app/solution/submission.parquet'); assert out.is_file() and not out.is_symlink()\nr=pd.read_parquet(out,columns=['uid','item_id','rank']); target=pd.read_parquet('/task/data/target_users.parquet').uid.to_numpy(np.int64); z=np.load('/task/data/test_eligible_candidates.npz')\nassert len(r)==len(target)*100 and all(np.issubdtype(r[c].dtype,np.integer) for c in r.columns) and np.isfinite(r.to_numpy()).all()\nassert set(r.uid)==set(target)==set(z['uids']); g=r.groupby('uid',sort=False)\nassert (g.size()==100).all() and (g.item_id.nunique()==100).all()\nassert all(np.array_equal(np.sort(s.to_numpy()),np.arange(1,101)) for _,s in g['rank'])\nitem_to_col={int(x):i for i,x in enumerate(z['item_ids'])}; uid_to_row={int(x):i for i,x in enumerate(z['uids'])}\nfor uid,s in g['item_id']:\n mask=np.unpackbits(z['packed_eligible'][uid_to_row[int(uid)]],count=len(z['item_ids']),bitorder='little')\n assert all(mask[item_to_col[int(item)]] for item in s)\nprint({'regular_file':True,'rows':len(r),'users':r.uid.nunique(),'rows_per_user':[int(g.size().min()),int(g.size().max())],'distinct_items_per_user':[int(g.item_id.nunique().min()),int(g.item_id.nunique().max())],'rank_range':[int(r['rank'].min()),int(r['rank'].max())],'all_test_eligible':True,'dtypes':{c:str(r[c].dtype) for c in r.columns}})\nPY"
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}
