| name | harness-implement |
| description | Orchestrate the entire IMPLEMENT phase — test-driven implementation of the approved plan, resolving build/type errors as they arise. Use after /harness-plan. Sequences /implement and /build-fix, delegates to subagents, and halts if reality diverges from the plan. |
/harness-implement — run the Implement phase
Thin orchestrator over the Implement skills. Requires an approved plan from
/harness-claude:harness-plan (or /harness-claude:plan). Refuse to start without one for non-trivial work.
Sequence
-
For each plan phase, in order:
/harness-claude:implement — delegate to the harness-claude:tdd-guide agent: failing test (RED) →
minimum code (GREEN) → refactor, against the phase's acceptance criteria.- Parallel-fan-out checkpoint (mandatory when it triggers): before editing a phase
serially, if it spans 3+ independent files with disjoint write-sets and no dependency, you
must surface
/harness-claude:orchestrate — name the file split and let the user choose.
The offer is not optional (that's the only way parallel mode fires); acting on it stays
opt-in — never auto-start a multi-agent run.
- Let the format/typecheck/quality hooks run; act on what they surface.
- If the build/types break and the fix isn't obvious →
/harness-claude:build-fix (delegate to
the harness-claude:build-error-resolver agent), minimal diffs only.
- Confirm the phase's exit check (tests green, build clean) before the next phase.
-
Plan-divergence gate: if reality contradicts the plan (a phase is wrong, missing,
or bigger than scoped), HALT — report the divergence, update the plan with the
user, then resume. Never silently improvise scope.
Rules
- Delegate search/exploration and isolated edits to cheaper models; keep the orchestrator
focused on integration.
- Files stay modular and lean (<800 lines), immutable patterns, validated inputs.
- Compact at phase boundaries, not mid-phase.
- Do not commit or push — branch creation follows
rules/git.md
(branch-at-first-write in /harness-claude:implement).
Output
Phase-by-phase summary (what was built, tests added, build status). Then hand off to
/harness-claude:harness-verify.
