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implementation-planner

@l-lin/dotfiles
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Break down technical implementation tasks into actionable steps with codebase analysis. Use when you need to decompose complex features, refactorings, or bug fixes into a structured implementation plan.

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SKILL.md

name implementation-planner
description Break down technical implementation tasks into actionable steps with codebase analysis. Use when you need to decompose complex features, refactorings, or bug fixes into a structured implementation plan.

Task Breakdown Protocol

You are invoked to break down a technical implementation task into concrete, actionable steps.

Analysis Phase

Step 1: Context Gathering

  1. Read all mentioned files immediately and FULLY:

    • Research documents, tickets, related plans
    • CRITICAL: Use Read tool WITHOUT limit/offset to read entire files
    • NEVER read files partially
  2. Spawn parallel research tasks to gather context:

    • Use @codebase-locator to find all files related to the task
    • Use @codebase-analyzer to understand current implementation
    • Use @git-investigator to understand why current implementation exists
    • Use @codebase-pattern-finder to find similar features to model after
  3. Wait for ALL sub-tasks to complete before proceeding

  4. Read all files identified by research tasks:

    • Read them FULLY into context
    • Cross-reference with requirements
    • Identify discrepancies
  5. Analyze and verify:

    • Note assumptions requiring verification
    • Determine true scope from codebase reality
    • Only ask questions that code investigation cannot answer

Breakdown Rules

Structure (MUST)

  • Each step must be specific and verifiable
  • Include file paths and function names where applicable
  • Order steps by dependency (prerequisites first)
  • Separate implementation from testing

Required Steps (MUST include)

  1. Test setup - Write test cases first (TDD approach)
  2. Implementation steps - Ordered by dependency
  3. Verification steps - Split into:
    • Automated verification: Tests, builds, linting (can be run by agents)
    • Manual verification: UI testing, performance checks (requires human)
  4. Cleanup step - Remove dead code, update docs if needed

Anti-patterns (AVOID)

  • Vague steps like "Update the logic"
  • Steps without file/function references
  • Missing verification steps
  • Skipping test-first approach

Output Format

Return a numbered list of tasks in this format:

1. Write tests for [feature] in [file:line]
   - GIVEN: [scenario]
   - WHEN: [action]
   - THEN: [expected outcome]

2. Implement [function] in [file:line]
   - [specific implementation detail]

3. Update [related code] in [file:line]
   - [what needs to change and why]

4. Run automated verification
   - [ ] Tests pass: `npm test` or `make test`
   - [ ] Build succeeds: `npm run build` or `make build`
   - [ ] Linting passes: `npm run lint` or `make lint`
   - [ ] Type checking passes: `npm run typecheck`

5. Run manual verification
   - [ ] [Specific UI feature works as expected]
   - [ ] [Performance acceptable under load]
   - [ ] [Edge case handling verified]
   - [ ] [No regressions in related features]

6. Cleanup (if needed)
   - Remove [deprecated code] from [file:line]
   - Update [documentation] in [file:line]

Verification Checklist

Each task should pass this check:

  • Can I execute this step without ambiguity?
  • Do I know which file and function to modify?
  • Is the expected outcome clear?
  • Can I verify this step independently?

Examples

Good Breakdown

1. Write test for user authentication in tests/auth.test.ts:45
   - GIVEN: User with valid credentials
   - WHEN: login() is called
   - THEN: Returns auth token and sets session cookie

2. Implement login() function in src/auth.ts:120
   - Hash password with bcrypt
   - Query users table for matching email
   - Generate JWT token on success
   - Set httpOnly session cookie

3. Update API route in src/api/auth.ts:30
   - Add POST /api/login endpoint
   - Call login() with request body
   - Return 200 with token or 401 on failure

4. Run automated verification
   - [ ] Unit tests pass: `npm test auth`
   - [ ] Integration tests pass: `npm test api/auth`
   - [ ] Type checking passes: `npm run typecheck`
   - [ ] No linting errors: `npm run lint`

5. Run manual verification
   - [ ] Login form works in browser
   - [ ] Session persists across page refresh
   - [ ] Invalid credentials show error message
   - [ ] Rate limiting prevents brute force

Bad Breakdown

1. Fix the authentication
2. Make sure it works
3. Test it

Problems: No file references, vague steps, no verification criteria

Sub-task Spawning Best Practices

When spawning research sub-tasks:

  1. Spawn multiple tasks in parallel for efficiency
  2. Each task should be focused on a specific area
  3. Provide detailed instructions including:
    • Exactly what to search for
    • Which directories to focus on
    • What information to extract
    • Expected output format
  4. Be EXTREMELY specific about directories:
    • Include full path context in prompts
  5. Request specific file:line references in responses
  6. Wait for all tasks to complete before synthesizing
  7. Verify sub-task results:
    • If sub-task returns unexpected results, spawn follow-up tasks
    • Cross-check findings against actual codebase
    • Don't accept incorrect results

Example spawning multiple tasks concurrently:

# Spawn these in parallel:
tasks = [
    Task("Research database schema", db_research_prompt),
    Task("Find API patterns", api_research_prompt),
    Task("Investigate UI components", ui_research_prompt),
    Task("Check test patterns", test_research_prompt)
]

Common Patterns

For Database Changes:

  1. Start with schema/migration
  2. Add store methods
  3. Update business logic
  4. Expose via API
  5. Update clients

For New Features:

  1. Research existing patterns first
  2. Start with data model
  3. Build backend logic
  4. Add API endpoints
  5. Implement UI last

For Refactoring:

  1. Document current behavior
  2. Plan incremental changes
  3. Maintain backwards compatibility
  4. Include migration strategy

Notes

  • Use existing codebase patterns (check before introducing new dependencies)
  • Keep scope focused (only touch relevant code)
  • Consider error handling in each step
  • Mark which steps require manual verification beyond tests
  • No open questions in final breakdown - resolve all uncertainties first