03 implement

Implement a feature from a prd.

Guardrails

• Follow the repo's AGENTS.md instructions (if present) for any files you touch.
• Keep changes simple and handoff-friendly: assume a junior dev (or another AI) will maintain this later.
• Do not change product scope while executing:
  • If the prd is missing details or ambiguous, stop and use 02-plan to refine the prd first.
  • If the feature is missing from tasks/todo.md, stop and use 01-new first.
  • If you discover out-of-scope requirements or bugs during execution, do not expand scope—create a new backlog item via 01-new instead.
• Do not edit tasks/todo.md except updating this feature's status indicator from — to 🔨 when implementation is complete.
• Do not reset any prd status checkboxes when updating an existing prd.

Workflow

1. Identify the prd

   • Ask for the prd path if not provided (usually tasks/f-##-<slug>.md).
   • Confirm which feature ID/name this prd corresponds to.

2. Pre-flight

   • Read AGENTS.md (if present) and follow it.
   • Check priority (if tasks/todo.md exists):
     • Priority is determined by list order.
     • If there are higher-priority items above this feature, ask the user to confirm they want to work on it now (vs a higher-priority item).
       • If the higher-priority item is unchecked (no prd yet), recommend writing its prd via 02-plan first.
   • Create a new feature branch before making changes (unless you are already on an appropriate feature branch):
     • Base it off the default branch (usually main) unless the repo has a different branching model.
     • Name it based on the prd Summary Type (or match repo conventions):
       • Type: fix → fix/f-##-<short-slug>
       • Type: chore → chore/f-##-<short-slug>
       • default (Type: feat) → feat/f-##-<short-slug>
   • If tasks/memory.md exists, skim key decisions / notes / gotchas relevant to this area before coding.
   • Parse the prd into an execution plan: user stories, functional requirements, non-goals, risks, rollout, and testing notes.
   • Verify dependencies:
     • Read this prd's "Dependencies & Constraints" section for feature dependency IDs.
     • For each dependency ID, locate the dependency's prd path from tasks/todo.md (or search tasks/ by ID if missing).
     • Check the dependency prd's ## Execution Status section.
     • If any dependency is not Implemented, recommend executing that dependency prd first.
     • If a dependency has no prd yet, stop and use 02-plan to create that dependency prd first.

3. Execute

   • Implement the feature as specified.
   • Add/update tests as appropriate.
   • Run the project's normal checks (typecheck/lint/tests/build) per AGENTS.md or project conventions.

4. Verify

   • Verify acceptance criteria and edge cases from the prd.
   • Perform any manual QA steps listed in the prd.

5. Update status (in-place)

   • Ensure the prd contains this section (add it if missing):

     ## Execution Status
     - [ ] Implemented
     - [ ] Reviewed
     - [ ] Merged
     

   • Check boxes based on evidence:

     • Implemented: code changes complete, tests added/updated and passing, acceptance criteria met locally. Also update the feature's status indicator in tasks/todo.md from — to 🔨.

   • If the prd has user-story checklists (e.g., - [ ] US-001 … and acceptance-criteria checkboxes), check them off as you complete them. Do not reset existing checkboxes.

6. Close out

   • Summarize what was changed and what remains.
   • Next steps:
     • If you want a PR: run 04-propose, then 05-review.
     • If you don't want a PR yet: run 05-review (local), then 06-memory.

Output

• Update code and tests as needed.
• Update the prd execution status checkboxes in the prd file.
• If you discover a durable decision/gotcha or complete a significant milestone, capture it in tasks/memory.md via 06-memory.
• Reply with:
  • prd path
  • Which execution status boxes were checked
  • Which status indicator was updated in tasks/todo.md (if any)
  • Any follow-ups or open issues