phase2-codegen

name	phase2-codegen
description	Generate production-quality code following acceptance criteria from refined issue, with comprehensive tests and documentation. Use after issue refinement (Phase 1) is complete.
argument-hint	[issue-number-or-description]

PHASE 2: CODE GENERATION

Generate complete, production-quality implementation from a refined issue.

Prerequisites: Issue has WHAT/WHY/HOW; user approved implementation.

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AGENT DELEGATION

Map the issue's HOW section to one of the developer agents installed alongside this skill:

Area of change	Developer agent
Backend / API	backend-developer
Frontend	frontend-developer
CLI	cli-developer
Marketing site	website-developer
Docs site	docs-site-developer

Delegate for service-specific changes. Self-implement for simple cross-cutting changes (small config/docs). For multi-service changes, run sequentially when dependent or in parallel when independent.

The delegation prompt template lives in the orchestrator workflow (github-issue-to-pr Step 2A).

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STEP 1: READ THE REFINED ISSUE

Extract: files to create/modify, functions/classes to implement, edge cases, tests to write. Map each acceptance criterion to the code that satisfies it.

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STEP 2: IMPLEMENT

For each component in HOW: create/open the file, implement with the exact names from HOW, handle the listed edge cases, add error handling. Follow the project's existing style, naming, file organization, and architectural patterns.

Required in all code:

• Imports grouped (stdlib, third-party, local), alphabetized, no unused
• Type hints / static types
• Docstrings on public functions, comments only for non-obvious logic
• Specific exceptions, not generic catches
• Constants instead of magic numbers/strings
• Clear names; one function = one responsibility
• DRY: extract repeated logic

Language pointers:

• Python: PEP 8, type hints, dataclasses, context managers, pathlib
• Go: idiomatic errors (fmt.Errorf with %w), defer cleanup, interfaces for abstractions
• TS/JS: const/let, async/await, strict types, project ESLint rules

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STEP 3: TESTS

For every new function: happy path, edge cases, error cases. Use AAA pattern (Arrange/Act/Assert).

• One test file per source file (test_<source>.py or similar)
• Unit tests mock external deps and run in milliseconds
• Integration tests cover end-to-end flows; mock external APIs but use real DB/FS where safe
• Each acceptance criterion has at least one test verifying it
• No flaky tests (no time.sleep, no unfixed randomness, no shared state)

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STEP 4: DOCUMENTATION

• Docstrings on every public function (args, returns, raises)
• Inline comments only for non-obvious logic
• Update README if public API changed, new feature added, install/config changed
• Update API docs if endpoints/schemas changed
• Document new env vars (purpose, default, valid range)

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STEP 5: DEPENDENCIES & CONFIG

• Add new packages to requirements/package.json with pinned versions; note purpose
• Update lock files
• New env vars: declare with defaults in code, document in .env.example and README
• Sensible defaults; document valid ranges

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STEP 6: VALIDATE AGAINST ACCEPTANCE CRITERIA

For each WHAT criterion, confirm: code implements it, a test would fail without it, you can demo it. Any unmet criterion blocks Phase 3 — implement and test it.

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SELF-CHECK BEFORE PHASE 3

# Python
pytest && ruff check . && mypy src/

# Go
go test ./... && golangci-lint run

# Node/TS
npm test && npm run lint && tsc --noEmit

No print statements, no commented-out code, no leftover TODOs, no debug logging.

For the canonical quality gate list see the quality-gates skill.

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EXIT CHECKLIST

• All HOW-section functions/classes implemented; edge cases handled; errors handled
• All new functions have tests; all acceptance criteria have tests; tests pass; coverage maintained or improved
• Docstrings on public functions; README/API/config docs updated as needed
• Deps + env vars + example configs in place
• Each WHAT criterion satisfied; implementation matches HOW (deviations documented)

Proceed to Phase 3 (phase3-rl-loop skill).