Feature Planning Skill

Plan implementation of new features with a user-centric, phased approach.

When to Apply

Activate when:

• Story title contains: Add, Create, Implement, Enable, Support, Build
• Story describes new user capability or functionality
• Story adds new features to the system
• User story follows "I want to [new capability]" pattern

Focus Areas

When planning feature stories, emphasize:

1. User Value: What user benefit is delivered?
2. Architecture: How does this fit existing systems?
3. Phases: Foundation -> Core -> Integration
4. Tests: Unit + Integration + E2E for user flows

Context Gathering

Before planning, read:

• Parent feature.json for feature context
• Parent prd.md for requirements and scope
• Existing codebase for patterns to follow
• Related implementations for consistency

Plan Output Format

Write to {story_path}/plan.md:

# Implementation Plan: {Story Title}

## Metadata
- **Story**: {story_id}
- **Feature**: {feature_id}
- **Type**: feature (inferred)
- **Created**: {timestamp}
- **Complexity**: {Low/Medium/High}

## User Story Summary
{Copy from user-story.md}

## Solution Statement
{How this feature delivers user value}

## Code Impact Matrix

| File | Action | Risk | Notes |
|------|--------|------|-------|
| path/to/file | Create/Modify | Low/Med/High | Description |

## Design Decisions

### Decision 1: {Topic}
- **Options**: A, B, C
- **Chosen**: {choice}
- **Rationale**: {why}

## Implementation Phases

### Phase 1: Foundation
**Goal**: {foundational work - data models, base infrastructure}

#### Step 1.1: {Task}
- **File**: `path/to/file`
- **Action**: Create/Modify
- **Details**: {what to do}
- **Validation**: {how to verify}

### Phase 2: Core Implementation
**Goal**: {main functionality - business logic, core features}

#### Step 2.1: {Task}
...

### Phase 3: Integration
**Goal**: {connect pieces - UI, API endpoints, integrations}

#### Step 3.1: {Task}
...

## Test Strategy

### Unit Tests
- [ ] {test case}

### Integration Tests
- [ ] {test case}

### E2E Tests (if UI)
- [ ] {user flow test}

## Acceptance Criteria Mapping

| Criterion | Verified By | Phase |
|-----------|-------------|-------|
| AC-1 | Unit test | 1 |
| AC-2 | E2E test | 3 |

## Rollback Plan
{How to undo if needed}

## Notes
{Additional considerations}

Constraints

• Follow existing patterns in the codebase
• Map every AC to a verification method
• Include tests throughout, not just at the end
• Consider error handling and edge cases

Applying This Skill

When creating a feature plan:

1. Start with user value proposition
2. Read parent feature context (feature.json, prd.md)
3. Analyze codebase for patterns and affected files
4. Create Impact Matrix with all files to touch
5. Break into 3 deliverable phases
6. Map each AC to implementation steps
7. Include comprehensive test strategy
8. Define rollback approach