trainer-train-code

# Trainer Train - Code Use this skill as the orchestration contract for one trainer run against a **Python code target** optimized through Microsoft Trace. The target is a Python file, function, helper, or agent component that benefits from test-based or benchmark-based feedback. Read `references/code-loop-contract.md` for the full routing table, Trace-specific patterns, feedback-signal rules, and validation constraints before any stage execution. ## When to use this skill - The selected target is a Python file or callable that should be improved with Microsoft Trace. - The caller needs to initialize or resume a trainer workspace for a code target. - Feedback signals exist as test results, benchmark scores, compiler errors, or deterministic evaluators. - The optimization stage returns a manual follow-up payload and the loop must continue. - A winning candidate needs to be validated against the test suite and written back. Do not use this skill for prompt-only targets, skill files, or agent contracts. Read the parent trainer skill's `references/target-routing.md` to identify the appropriate specialist for those target types. ## Required inputs - One selected Python target file or component boundary. - Repository root or enough path context to derive the local trainer workspace. - The feedback command: test suite, benchmark script, or deterministic evaluator (e.g., `python -m pytest -q`). - The concrete stage capability map: researcher, synthesizer, optimizer, elector. - The candidate trainable surface: which parts should become Trace nodes, bundles, or models. - Any existing workspace artifacts, test results, or Trace configurations to reuse. ## Code-specific loop rules ### Trace surface selection Choose the smallest trainable surface that Trace should control: - Use `trace.node(trainable=True)` for mutable values: prompts, instruction strings, thresholds, templates, routing labels. - Use `@trace.bundle(trainable=True)` for a callable whose behavior should be optimized as a unit: formatters, extractors, classifiers, repair functions. - Use `@trace.model` when several trainable nodes and bundles belong to one coherent object. - Leave orchestration, I/O, and stable business logic as plain Python outside the trainable surface. ### Judge mode Code targets use **custom** scoring mode by default. Executable feedback (test pass/fail, benchmark scores, compiler errors) is authoritative. Use `llm_judge` only as a secondary signal when tests explain *what* failed but not *how* to improve it. Treat an explicit row-level `scoring` declaration as authoritative. ### Feedback signal discipline - Reset feedback each iteration before the next backward pass. - Preserve failed executions and feed them back through `ExecutionError` when the failure itself is informative. - Prefer deterministic, repeatable checks over subjective critiques whenever possible. - If no feedback signal can be deterministically rerun, stop and report a blocker. ### Import and dependency hygiene - Keep Trace imports explicit and local to the trainable surface. - Call out hidden dependencies inside trainable bundles before optimization begins. - Warn when a trainable surface is too broad to produce attributable feedback. ## Core workflow Follow this order. Consult `references/code-loop-contract.md` when artifact paths, Trace patterns, or feedback-signal choices are uncertain. 1. **Resolve target and workspace.** Derive `<code-name>` from the selected file using the canonical rule: strip only `.md` for `.md` files; for `.prompty` strip entirely; otherwise use `Path.stem`. For a typical Python file (`config.py`), strip `.py` to get `config`. Use `<target-dir>/.trainer-workspace/<code-name>/` as workspace root. If state indicates a resumed run, audit tracked artifact pointers and skip only stages that already produced valid outputs. 2. **Require the workspace review checkpoint.** Confirm the engineering review artifact exists before optimization starts. Report a blocker if it is absent. 3. **Initialize or refresh workspace.** Create or update `workflow-status.json`, source snapshot, the review subdirectory, `inputs/source/`, and `iterations/` directories. 4. **Identify the trainable surface.** Confirm which code boundaries should become Trace nodes, bundles, or models. Record the trainable surface in the workspace before optimization. 5. **Inspect existing datasets and evals.** Prefer reuse when train, validation, and authored eval assets already fit the code target and feedback signal. Keep authored evals, train data, and validation data as separate artifacts. 6. **Run missing-data path if needed.** If any required dataset or feedback-signal script is absent, pause optimization and gather them via the caller-supplied researcher and synthesizer. 7. **Infer judge mode.** Default to `custom` scoring for code targets. Treat explicit row-level `scoring` as authoritative. Stop and report inconsistency if train and validation splits imply different modes. 8. **Run at least one optimization pass.** Pass the inferred judge mode, the trainable surface description, and the feedback command to the optimizer. 9. **Handle manual follow-up if returned.** Save the report as `manual-followup-report.json`, answer the model-facing prompt, persist the candidate artifact, and continue the loop. 10. **Run election if multiple candidates exist.** Use the caller-supplied elector when optimization produces more than one defensible candidate. 11. **Publish iteration artifacts.** Stage steering, candidate bundles, validation logs, and a decision summary under the active iteration directory. 12. **Write back only when validation passes.** Confirm the test suite passes and the decision summary justifies write-back before persisting the winning candidate. ## Blocker-first rule Stop and report a clear blocker before any optimization or rewrite when: - The workspace review artifact is absent. - No repeatable feedback signal exists (tests, benchmarks, or evaluator script). - The trainable surface is undefined or too broad to produce attributable feedback. - Tracked artifact pointers from a resumed run are missing or inconsistent. A blocker report must name the missing artifact or undefined boundary, explain why the loop cannot advance, and leave `workflow-status.json` in a resumable checkpoint state. ## Output contract Return: 1. Workspace status and any active blockers. 2. Current-turn decisions: trainable surface, judge mode, selected branch, blockers. 3. Optimization or manual follow-up status with artifact paths. 4. Feedback signal confirmation (test command and expected signal shape). 5. Validation status (test suite pass/fail). 6. Write-back decision and justification. 7. Next required action to resume or continue the loop.