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name: planning-methodology description: Create minimal-change, reversible implementation plans. Transform requirements into executable blueprints emphasizing simplicity and safety. auto_invoke: true tags: [planning, architecture, minimal-change, reversibility] version: 0.1.0 source: fork checksum: 79c5b626d9a7c520d02089aef93ccd6ebcbb3b8698415290e5c4c99b71d2ab05 updated_at: 2026-02-11T09:29:29+08:00

Planning Methodology Skill

This skill provides a systematic methodology for creating implementation plans that are surgical, reversible, and minimize risk while maximizing clarity.

When Codex Should Use This Skill

Codex will automatically invoke this skill when:

• ResearchPack is ready and implementation planning is needed
• User asks "how should we implement...", "create a plan for..."
• Complex feature requires structured approach
• Need to break down requirements into executable steps
• Transforming research into actionable blueprint

Core Principles (BRAHMA Constitution)

1. Simplicity over complexity (KISS, YAGNI)
2. Minimal changes only - Touch fewest files possible
3. Reversibility mandatory - Every change must be undoable
4. Verification at each step - Clear success criteria

Planning Methodology Protocol

Step 1: Codebase Discovery (< 90 seconds)

Objective: Understand existing structure before planning changes

Actions:

1. Structure scan (use Glob tool):

   Search patterns:
   - Source files: src/**/*.{ext}
   - Config files: *.config.{ext}, .{ext}rc
   - Test files: **/*.test.{ext}, **/*.spec.{ext}
   - Documentation: docs/*.md, README.md
   

2. Pattern recognition (use Grep + Read):

   • How similar features are currently implemented
   • Naming conventions (file names, function names)
   • Code style (indentation, formatting)
   • Import/export patterns
   • Test patterns and frameworks

3. Integration point identification:

   • Where does new code connect to existing code?
   • Configuration files that need updates
   • Entry points (main.ts, index.js, etc.)
   • Dependency injection patterns

4. Constraint discovery:

   • Existing dependencies that limit choices
   • Framework conventions that must be followed
   • Security/auth patterns that must be maintained
   • Performance SLAs to meet

Output:

Codebase Profile:
- Primary language: [TypeScript/Python/Go/etc.]
- Framework: [Next.js/Django/Gin/etc.]
- Structure: [src/ organization pattern]
- Test framework: [Jest/pytest/etc.]
- Key patterns: [Dependency injection / Factory / etc.]
- Integration points: [config.ts, app.ts, etc.]

Anti-stagnation: Max 90 seconds - if codebase is large, focus on areas relevant to feature only

Step 2: Minimal Change Analysis (< 60 seconds)

Objective: Identify the smallest set of changes that accomplishes the goal

Questions to answer:

1. New vs Modify:

   • Can we extend existing code (better) or must we modify it?
   • Can new functionality live in new files (preferred)?
   • What's the smallest interface between new and existing code?

2. Reuse vs Rebuild:

   • What existing utilities/services can be reused?
   • What patterns can we follow from similar features?
   • What must be built from scratch (minimize this)?

3. Scope boundaries:

   • What's the absolute minimum to make feature work?
   • What's "nice to have" that can be deferred?
   • What edge cases must be handled vs can be documented as limitations?

4. Reversibility:

   • How easily can each change be undone?
   • Are we modifying core/critical files (higher risk)?
   • Can we use feature flags for gradual rollout?

Output:

Minimal Change Strategy:
- New files: [N] (primary work here)
- Modified files: [N] (minimal edits)
- Deleted files: 0 (avoid deletions, use deprecation)
- Core files touched: [N] (minimize this)
- Reversibility: [Git revert / Config toggle / Feature flag]

Principles:

• Prefer extension over modification
• Prefer new files over editing existing
• Prefer configuration over code
• Prefer composition over inheritance

Step 3: Risk Assessment (< 30 seconds)

Objective: Identify what could go wrong and plan mitigations

Categories of risk:

1. Breaking changes:

   • Will this affect existing functionality?
   • Are we modifying shared/core modules?
   • Could this break other features?

2. Performance risks:

   • Will this add latency to critical paths?
   • Memory/CPU impact on existing operations?
   • Database query performance degradation?

3. Security risks:

   • Does this handle user input (validate & sanitize)?
   • Are credentials/secrets managed properly?
   • Could this introduce injection vulnerabilities?

4. Integration risks:

   • Dependencies on external services (what if they're down)?
   • API version mismatches?
   • Race conditions or concurrency issues?

5. Testing gaps:

   • What's hard to unit test (integration test instead)?
   • What scenarios might we miss?
   • What's the fallback if tests don't catch an issue?

For each identified risk:

Risk: [Description]
Probability: [High/Medium/Low]
Impact: [High/Medium/Low]
Mitigation: [How to prevent]
Detection: [How we'll know if it happens]
Contingency: [What we'll do if it happens]

Anti-pattern: Don't identify risks without mitigations - every risk needs an answer

Step 4: Implementation Sequence (< 30 seconds)

Objective: Order the work for safety and clarity

Sequencing principles:

1. Dependencies first: Build foundation before dependent features
2. Tests alongside: Write tests as you implement (or before - TDD)
3. Incremental integration: Connect to existing system gradually
4. Verification checkpoints: Each step has clear pass/fail criteria

Step structure:

Step N: [Action verb] [What]
- Task: [Detailed description]
- Files: [Which files to change]
- Code: [Specific code examples]
- Verification: [How to confirm success]
- Time estimate: [X minutes]

Verification methods:

• Unit test passes: npm test path/to/test
• Build succeeds: npm run build
• Manual check: "Navigate to X and confirm Y is visible"
• Integration test: npm run test:integration
• Performance check: npm run benchmark (if applicable)

Total time estimate: Sum of all step estimates + 20% buffer

Step 5: Rollback Planning (< 20 seconds)

Objective: Ensure every change can be undone safely

Rollback mechanisms (in priority order):

1. Git revert (simplest):

   git reset --hard [checkpoint-commit]
   

   Good when: All changes in one commit, no DB migrations

2. Feature flag toggle (gradual rollout):

   if (featureFlags.newFeature === true) {
     // new code
   } else {
     // old code
   }
   

   Good when: Want to test in production, quick rollback needed

3. Configuration rollback: Restore previous config files Good when: Changes are mostly configuration-driven

4. Partial rollback: Keep working parts, revert broken parts Good when: Multiple independent changes, some work

Rollback plan must include:

• Exact commands to execute
• Verification steps after rollback
• Data migration rollback (if DB changes made)
• Cache invalidation (if caching involved)

Rollback triggers (when to execute rollback):

• Tests fail in production
• Performance degrades > [threshold]%
• Error rate increases > [threshold]%
• Critical functionality breaks

Step 6: Plan Documentation (< 30 seconds)

Objective: Structure all above findings into clear, executable plan

Implementation Plan Format:

# 🗺️ Implementation Plan: [Feature Name]

## Summary
[2-3 lines: what + why + approach]

## 📁 File Changes
[New: N, Modified: N, with specific purposes]

## 🔢 Implementation Steps
[Numbered steps with verification]

## 🧪 Test Plan
[Unit + integration + manual tests]

## ⚠️ Risks & Mitigations
[Each risk with mitigation and contingency]

## 🔄 Rollback Plan
[Exact rollback procedure]

## ✅ Success Criteria
[Clear definition of "done"]

Checklist before delivering:

• ✓ Every file change has a clear purpose
• ✓ Every step has verification method
• ✓ All risks have mitigations
• ✓ Rollback plan is complete and tested (if possible)
• ✓ Success criteria are measurable
• ✓ Time estimates are realistic

Quality Standards

Completeness

• File changes: Specify exact files with line-level changes where possible
• Steps: Each step is atomic (can be done and verified independently)
• Tests: Cover happy path + at least 2 edge cases + 1 error case
• Risks: All major risks identified (breaking, performance, security)

Clarity

• Actionable: Developer can execute without additional questions
• Verifiable: Each step has objective pass/fail criteria
• Unambiguous: No "probably" or "maybe" - specific instructions only

Safety

• Reversible: Every change can be undone
• Incremental: Changes build up gradually (not big bang)
• Validated: Tests verify correctness at each step
• Isolated: Failure of one step doesn't break entire system

Common Pitfalls to Avoid

❌ Don't:

• Plan modifications to many files simultaneously (hard to verify)
• Skip risk assessment ("hope for the best")
• Forget rollback plan
• Make plans that require perfect execution (allow for errors)
• Over-engineer ("we might need this someday")
• Under-estimate time (plans should be realistic)

✅ Do:

• Touch fewest files possible (minimal blast radius)
• Identify risks and plan mitigations explicitly
• Always include rollback procedure
• Build in verification checkpoints at every step
• Follow YAGNI (You Aren't Gonna Need It) - only what's needed now
• Add 20% time buffer for unexpected issues

Integration with knowledge-core.md

Before planning: Read knowledge-core.md to check for:

• Architectural patterns established in past projects
• Decisions that constrain current work
• Known gotchas in this codebase

After planning: If plan establishes new patterns, note for knowledge-core update:

New Pattern Established:
- Pattern: [Name/description]
- Context: [When to use this]
- Example: [Which files demonstrate this]

Performance Targets

• Total planning time: < 3 minutes for typical features
• Plan accuracy: 95%+ of files identified correctly
• Risk coverage: 100% of major risks identified
• Time estimates: Within 30% of actual implementation time

Example Usage

Scenario: ResearchPack ready for Redis caching, need implementation plan

Codex (using this skill):

[Internal: Need to plan Redis integration systematically]

📐 Activating planning-methodology skill

🔎 Analyzing codebase structure...
[Follows methodology: discover → analyze → assess → sequence → rollback → document]

# 🗺️ Implementation Plan: Redis Caching

## Summary
Add Redis-based caching layer to ProductService to reduce database load.
Approach: Create separate CacheService wrapper, inject into ProductService,
maintain backward compatibility via optional usage.

## 📁 File Changes (5 files)

### New Files (2)
1. `src/services/CacheService.ts` (~80 lines)
   - Purpose: Redis client wrapper with get/set/del/ttl operations
   - Exports: CacheService class
   - Dependencies: redis@4.6.0, config

[...rest of detailed plan following format]

✅ Plan ready for implementation

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This skill ensures plans are safe, minimal, clear, and executable - setting up @code-implementer for success.