Implement Feature Skill

Executes TDD implementation in a worktree. Creates the worktree, runs TDD, verifies action items and acceptance criteria, then returns control to the caller for validation and merge.

Workflow

Step 0: Exit Plan Mode

If you are in plan mode: Call ExitPlanMode() immediately. Do not explore files, do not read code, do not create plans. Wait for user approval then continue with Step 3.

Step 1: Prepare Worktree

Check session context for worktree parameters:

identifier: TASK-NNN or FEATURE-slug
title: Feature/task title

If not already in worktree:

If no identifier create a new identifier yourself in the format FEATURE-slug. Otherwise, use the identifier provided.

You MUST call the Skill tool now: Skill(skill="groundwork:use-git-worktree", args="<identifier>")

Do NOT create branches or worktrees with git commands directly. The skill handles setup and baseline validation.

Wait for worktree creation to complete and baseline tests to pass.

If already in worktree (.worktrees/ in pwd):

Use existing worktree context. Go to step 2.

Step 2: Gather Context

Check if action items and acceptance criteria are available from the current session context (e.g., from execute-task or build-unplanned-feature).

If context available: Use action items and acceptance criteria from session.

If context NOT available: Use AskUserQuestion to ask:

"What should be implemented? Please provide Action Items (what needs to be done) and Acceptance Criteria (how we'll know it's done)."

Wait for user response before proceeding.

Store the gathered context for use in subsequent steps.

Step 3: Execute TDD

You MUST call the Skill tool now: Skill(skill="groundwork:test-driven-development")

Do NOT write implementation code without first loading the TDD skill. It enforces red-green-refactor discipline.

For each action item:

Write failing test
Implement minimum code to pass
Refactor if needed
Verify test passes

Complete all action items before proceeding.

Step 4: Demand Elegance

For non-trivial changes, ask:

"Is there a more elegant way to implement this?"

Read docs/clean-code-principles.md now using the Read tool, then apply its guidance on:

Simpler abstractions
Better naming
Reduced complexity
Cleaner interfaces

If improvements identified: implement them (maintaining test coverage).

Step 5: Verify and Hand Off

Verify all work before handing off:

Action Items - Each implemented and tested
Test Coverage - All new code has tests, all pass
Acceptance Criteria - Each verified

If any fail: Do not proceed. Continue working until all pass.

Commit all changes:

git add -A && git commit -m "<identifier>: Implementation complete"

Capture worktree info:

worktree_path: Result of pwd
branch: Result of git branch --show-current
base_branch: The branch the worktree was created from (typically main or the branch active before worktree creation)

Output the following block exactly:

IMPLEMENTATION_READY
worktree: <worktree_path>
branch: <branch>
base-branch: <base_branch>
identifier: <identifier>

Then output verification results:

## Verification Results

### Action Items
- [x] [Action 1] - Implemented in `file.ts`, tested in `test.ts`

### Test Results
- All tests pass: [yes/no]

### Acceptance Criteria
- [x] [Criterion 1] - Verified by [method]

Return control to the caller. Do NOT run validation-loop, merge, or report completion.

Reference

Session Context Parameters

When called from parent skills, these parameters are passed via session context:

Parameter	Description	Example
`identifier`	Task or feature ID	`TASK-004`, `FEATURE-user-login`
`title`	Human-readable title	"Add user authentication"
`action-items`	List of work items	From task file or requirements
`acceptance-criteria`	Verification criteria	From task file or requirements

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