Implement Feature

Execute the tasks from the task list to build the feature. Works through tasks in dependency order, checking off completed items as it goes.

Usage

/spec-kit:implement

Optionally specify a spec: /spec-kit:implement 001 or /spec-kit:implement user-auth

Process

Step 1: Get Current Spec Context

Use the get-current-spec skill to determine which spec to work with.

The skill will:

1. Check if user mentioned a spec in their input (e.g., "001", "user-auth")
2. Read from progress.yml if no spec mentioned
3. Prompt user to select if neither available
4. Update progress.yml via set-current-spec skill when a new spec is chosen

After the skill completes, you will have:

• Feature number: {NNN}
• Feature name: {feature-name}
• Feature directory: .claude/spec-kit/specs/{NNN}-{feature-name}/

Step 2: Load All Artifacts

Read the complete context:

cat .claude/spec-kit/memory/constitution.md
cat .claude/spec-kit/specs/{NNN}-{feature-name}/spec.md
cat .claude/spec-kit/specs/{NNN}-{feature-name}/plan.md
cat .claude/spec-kit/specs/{NNN}-{feature-name}/tasks.md

If any are missing, direct user to appropriate command.

Step 3: Check for Consistency Issues

Remind user to run analysis if they haven't:

⚠️ Recommendation: Run /spec-kit:analyze first to check for consistency issues.

If the user wants to proceed anyway, continue.

Step 4: Review Task Status

Parse tasks.md to find:

• Total tasks: {count}
• Completed: {count}
• In Progress: {count}
• Not Started: {count}

Decision Point:

• If tasks are already in progress, ask if user wants to continue from where they left off or start fresh
• Show which task was in progress

Step 5: Select Starting Task

Find the next task to work on:

• Not started with dependencies satisfied
• Follow dependency order (Phase 1 → Phase 2 → Phase 3)
• Within a phase, prioritize by: High priority → Medium → Low

Show the selected task:

📋 Next Task: Task 1.2 - Set Up Database Schema

Priority: High
Complexity: Medium
Estimated: M (1 day)
Dependencies: ✅ Task 1.1 (completed)

Description:
Create database schema for user authentication with users table and sessions table.

Ready to start? (y/n)

Step 6: Execute Task

For the selected task:

1. Mark as In Progress

   • Update tasks.md: Change status from ⬜ to 🟡
   • Write the updated tasks.md

2. Review Task Details

   • Read acceptance criteria
   • Note files to create/modify
   • Review implementation notes
   • Check testing requirements

3. Implement the Task

   • Create or modify files as specified
   • Follow patterns from the plan
   • Adhere to constitution standards
   • Write clean, well-documented code

4. Verify Acceptance Criteria

   • Go through each checkbox
   • Validate the criteria is met
   • If not met, continue working

5. Run Tests (if applicable)

   • Run unit tests for the task
   • Run integration tests if needed
   • Fix any failures

6. Mark as Complete

   • Update tasks.md: Change status from 🟡 to ✅
   • Check all acceptance criteria boxes
   • Update task summary counts

Step 7: Move to Next Task

After completing a task:

✅ Task 1.2 Complete: Set Up Database Schema

Files Modified:
- src/database/schema.sql
- src/models/User.ts
- src/models/Session.ts

Tests: ✅ All passing (12 tests)

Progress: 2/15 tasks complete (13%)

Next task available: Task 1.3 - Create Auth Service
Continue? (y/n)

If user says yes, repeat Step 6 for the next task. If user says no, save progress and exit.

Step 8: Handle Blockers

If you encounter a blocker:

Technical Blocker:

• Document the issue in implementation notes
• Mark task as blocked with reason
• Suggest how to unblock
• Ask user for guidance

Requirement Ambiguity:

• Flag the unclear requirement
• Suggest running /spec-kit:clarify to resolve
• Pause implementation until clarified

Dependency Missing:

• Check if dependency task is complete
• If not, suggest completing that first
• If complete but still blocking, investigate why

Step 9: Phase Completion

When all tasks in a phase are complete:

🎉 Phase 1 Complete: Foundation

Completed Tasks: 5/5
- ✅ Task 1.1: Project setup
- ✅ Task 1.2: Database schema
- ✅ Task 1.3: Auth service
- ✅ Task 1.4: API routes
- ✅ Task 1.5: Basic tests

Next Phase: Phase 2 - Core Features (8 tasks)

Ready to continue with Phase 2? (y/n)

Step 10: Feature Completion

When all tasks are complete:

🎊 Feature Complete: {NNN}-{feature-name}!

Implementation Summary:
- Total Tasks: 15
- Completed: 15
- Time Taken: {actual time if tracked}
- Files Created: {count}
- Files Modified: {count}
- Tests Written: {count}

Final Steps:
1. Review all changes: git diff main
2. Run full test suite: npm test
3. Manual testing of user flows
4. Code review preparation
5. Deployment planning

Recommendations:
- Update spec.md if requirements changed during implementation
- Update plan.md with lessons learned
- Document any deviations from original plan
- Consider writing a post-mortem or summary

Ready to commit? Use /commit to create a commit with the changes.

Best Practices

Work in Small Increments

• Complete one task at a time
• Commit after each task or phase
• Test continuously
• Don't skip ahead

Follow the Plan

• Stick to the plan unless there's a good reason to deviate
• If you deviate, document why
• Update the plan if you learn something new

Test as You Go

• Write tests alongside implementation
• Run tests after each task
• Don't accumulate testing debt

Ask for Help

• If stuck for >30 minutes, ask user
• Don't make assumptions about requirements
• Clarify ambiguities immediately

Keep Tasks Updated

• Update status in real-time
• Check off acceptance criteria as met
• Add notes about challenges or learnings

Handling Common Situations

Task Seems Too Large

If a task is taking much longer than estimated:

• Break it into subtasks
• Complete what you can
• Mark original task partially complete
• Add new tasks for remaining work

Requirements Changed

If requirements change during implementation:

1. Pause implementation
2. Document the change
3. Update spec.md
4. Update plan.md and tasks.md if needed
5. Get user approval
6. Resume implementation

Discovered Technical Issue

If you find a technical problem not anticipated in the plan:

1. Document the issue
2. Propose solution options
3. Update plan with chosen approach
4. Add tasks if needed
5. Continue implementation

Tests Failing

If tests fail:

1. Don't mark task complete
2. Fix the failures
3. Re-run tests
4. Only mark complete when tests pass

Error Handling

• If tasks.md doesn't exist, direct to /spec-kit:tasks
• If no tasks are ready (dependencies), show dependency tree
• If encountering code errors, debug and fix them
• If uncertain about implementation, consult plan and spec

Notes

• Implementation can be paused and resumed anytime
• Tasks.md tracks your progress
• You can implement tasks out of order if dependencies allow
• It's OK to add new tasks if you discover more work
• Update estimates if actual effort differs significantly
• Document lessons learned for future planning
• The goal is to ship the feature, not to follow the plan perfectly