Execute an implementation plan step by step with verification checkpoints and progress tracking. Use when the user asks to "implement the plan", "execute the steps", "start implementing", or has an approved plan ready to implement.

Execute a structured implementation plan. Work through each step with developer oversight.

Phase 1 — Locate the Plan

Find the plan to execute:

If the developer specifies a file, use it.
Otherwise, search for recent plan-*.md or implementation plan files in the working directory.
If multiple candidates exist, ask which one to use.

Read the plan. Summarize: what will change, how many steps, which files are affected. Ask the developer to confirm before touching any files.

Phase 2 — Execute Steps

For each numbered step in the plan:

Announce — state which step is being executed and what it involves.
Implement — make the change as specified.
Verify — if the plan includes verification for this step (test commands, expected behavior), run it. If not, confirm the change looks correct in context.
Report — brief result before moving to the next step.

If something unexpected comes up during a step (a file doesn't exist, a function signature changed, a test fails), stop and surface it to the developer. Do not improvise fixes outside the plan scope.

Phase 3 — Verification

After all steps are complete, run any verification commands specified in the plan:

Automated tests
Build commands
Manual verification steps (describe what to check)

Report pass/fail for each.

Phase 4 — Summary

Provide:

Steps completed
Files modified
Tests run and results
Any deviations from the plan (with reasoning)
Any new issues discovered (for separate follow-up)

Constraints

Stay in scope. Implement exactly what the plan specifies. If something adjacent needs fixing, note it — do not fix it.
Do not commit. The developer decides when to commit.
Do not deploy. No deploy or push commands.
Surface surprises. If reality doesn't match the plan, stop and ask rather than guessing.