implement

/implement — build it, test-first

Goal: turn the plan into working, tested, clean code — one phase at a time.

Do this

1. Take the plan's phases in order. For each phase:
   • Delegate to harness-claude:tdd-guide (or run TDD inline): write a failing test against an acceptance criterion (RED) → minimum code to pass (GREEN) → refactor.
   • Keep files modular and lean (<800 lines), immutable patterns, inputs validated.
   • Let the format/typecheck hooks run; fix what they flag immediately.
2. Parallel-fan-out check. If a phase (or the plan) spans 3+ independent files with disjoint write-sets and no dependency between them, offer to fan the work out via /harness-claude:orchestrate instead of editing serially. Opt-in — propose it and let the user choose; never silently start a multi-agent run (it spawns workers and costs more tokens).
3. After each phase, confirm its exit check (test green, build clean) before moving on.
4. If the build breaks and the fix is non-obvious, hand off to /harness-claude:build-fix.
5. Stay inside the plan. If reality diverges from it, stop, update the plan, then resume — don't silently improvise scope.

Token discipline

Delegate search/exploration and isolated edits to cheaper models; keep the orchestrator focused on integration. Compact at phase boundaries, not mid-phase.

Exit criterion

All phases complete, tests written-first and green, build/types/lint clean. Then proceed to the Verify phase (/harness-claude:review).