Subagent Driven Development

Subagent-Driven Development Skill

Execute a plan with fresh implementers. Planning owns the plan format; this skill owns task dispatch and integration. Check requirements before code quality. Use the review lane in skills/process/pr-workflow/SKILL.md to choose direct or independent review; do not add another roster to a completed review.

Instructions

Phase 1: SETUP

Step 1: Read plan and extract tasks

Read the plan once. For each task, retain its full text, files, dependencies, and verification commands. Pass these inline rather than sending workers back to the plan.

Step 2: Create TodoWrite

Track all tasks as pending, in progress, or complete with TodoWrite or the harness's task tracker. Reuse the existing plan; do not create a second status artifact.

Step 3: Gather scene-setting context

Capture git status, project conventions from CLAUDE.md, relevant code patterns, dependencies, and setup requirements. Capture BASE_SHA with git rev-parse HEAD before the first implementer: it anchors the final integration diff. Include the context each worker needs in its dispatch.

Step 4: Determine parallel vs sequential dispatch (scope-overlap check)

python3 scripts/check-scope-overlap.py \
  --tasks '[{"id":"task-1","scope":["path/a.py"]},{"id":"task-2","scope":["path/b.py"]}]' \
  --human   # --check: exit 0 for no conflicts, 1 for conflicts

Each task has an id and scope path list. Directories include descendants; "readonly": true marks read-only tasks. Use the reported parallel groups, then account for dependencies: serialize overlapping writes and tasks that consume earlier results. Independent groups may run in parallel.

Gate: Full tasks, BASE_SHA, context, dependencies, and checked file scopes are ready.

Phase 2: EXECUTE (Per-Task Loop)

Step 1: Mark task in_progress

Update the task tracker.

Step 2: Dispatch implementer subagent

Use ./implementer-prompt.md with full task text, relevant context, deliverables, and checks. Resolve material questions from available evidence; ask the user only when their decision is needed.

Allocate one implementation worktree per task and reuse it for corrections. Before creating it, run the capacity guard from worktree-agent; at the hard threshold, reclaim accepted clean checkouts. Reviewers read the committed candidate with git diff or git show and need no worktree.

For executor-ready plans, append the template's Executor-Ready Plans contract. Keep the plan-creation SHA distinct from execution BASE_SHA. The implementer checks ancestry and context drift, runs each step's verify command, and stops for drift, two verification failures, scope violations, ambiguous or missing instructions, or test regression. The complete contract lives in skills/process/planning/references/executor-ready-plan-template.md; do not weaken it during dispatch.

Implementers understand the task, implement with TDD where appropriate, run relevant and required checks, self-review, and commit. Use verification-before-completion for verification rules. A still-valid passing check does not need repeating merely because the task reaches another phase.

Step 3: Dispatch ADR compliance reviewer subagent

Check the implementation against requirements and any applicable ADR: missing work, unwanted additions, and mismatches. For an independent review, use ./adr-reviewer-prompt.md. For a direct review lane, the coordinator performs this check. Reuse review of the same candidate and scope.

Fix requirement failures before code-quality review. Reuse the task worktree and provide precise corrections. After three failed reviews at this stage, stop the loop, report the findings and attempted fixes, and request the decision needed to resolve the conflict.

Step 4: Dispatch code quality reviewer subagent

After requirements pass, check structure, meaningful tests, error handling, and bugs. For an independent review, use ./code-quality-reviewer-prompt.md; otherwise review directly. Fix Critical and Important findings; Minor findings are optional. Recheck affected findings and behavior after fixes. After three failed reviews at this stage, stop and report the unresolved decision as in Step 3.

Step 5: Mark task complete

Record both results:

Task [N]: [Title] -- COMPLETE
  ADR compliance: PASS
  Code quality: PASS

When no ADR applies, label the first result Requirements: PASS instead. Do not report an independent review if the check was direct. Continue with the next ready task.

After integration accepts the task, verify its worktree is clean and inactive, then run git worktree remove -- <path>. Preserve the branch until normal merged-branch cleanup proves it disposable.

Gate: Requirements and code quality pass; task status records completion.

Phase 3: FINALIZE

Step 1: Final integration review

Review the combined BASE_SHA..HEAD diff for cross-task conflicts, duplicate utilities, incompatible patterns, and broken integration. Use independent review when the selected lane requires it or unresolved risk warrants it. Reuse completed review that covers this combined candidate. Run required integration checks and tests affected by combining the tasks.

Step 2: Complete development workflow

Follow the authorized completion path: pr-workflow for a PR, authorized merge, or keeping the branch. Do not ask again for an action already authorized.

Gate: Combined changes work together, required checks pass, and the requested delivery is complete.

Error Handling

References

• implementer-prompt.md: implementation dispatch and executor-ready contract.
• skills/process/planning/references/executor-ready-plan-template.md: plan schema, drift checks, verification, and STOP conditions.
• adr-reviewer-prompt.md: requirements review.
• code-quality-reviewer-prompt.md: code-quality review.