Codebase Analysis Skill

This skill provides systematic approaches to analyzing and understanding codebases of any size and complexity.

Analysis Strategy by Project Size

Small (<50 files):     Comprehensive scan of all files
Medium (50-500 files): Representative sampling per category
Large (>500 files):    Strategic sampling of key areas

Parallel Analysis Tracks

Run these tracks concurrently for efficiency:

Track 1: Product Understanding

# Files to examine:
- README.md, README*.md
- package.json "description" field
- docs/ or documentation/ folder
- Main entry points (index.ts, main.ts, app.ts)
- API documentation

Track 2: Technical Stack Discovery

# Configuration files:
- package.json (dependencies, devDependencies, scripts)
- tsconfig.json / jsconfig.json
- Build configs: vite.config.*, webpack.config.*, rollup.config.*
- Test configs: jest.config.*, vitest.config.*
- Linter configs: .eslintrc.*, eslint.config.*
- Formatter configs: .prettierrc.*, prettier.config.*

Track 3: Structure Mapping

# Analyze:
- Top-level directories (src/, lib/, packages/, apps/)
- 2-3 representative files per major directory
- Naming conventions (kebab-case, camelCase, PascalCase)
- Module organization patterns
- Index/barrel files

Track 4: Convention Detection

# Patterns to identify:
- Export style: named vs default exports
- Component patterns: functional vs class, HOCs
- State management: Redux, Zustand, Context
- Testing patterns: unit, integration, e2e
- Error handling: try/catch, Result types, error boundaries

Analysis Output Templates

Package Analysis

## Package: {name}

**Purpose**: {description}
**Type**: Library | Application | CLI | Framework
**Entry**: {main entry point}

### Dependencies
- Production: {count} packages
- Development: {count} packages
- Key deps: {list critical dependencies}

### Scripts
| Script | Command | Purpose |
|--------|---------|---------|
| dev | {cmd} | Development server |
| build | {cmd} | Production build |
| test | {cmd} | Run tests |

Directory Analysis

## Directory: {path}

**Purpose**: {description}
**Pattern**: {naming convention}
**File Count**: {count}

### Structure
{tree representation, 2-3 levels}

### Key Files
| File | Purpose |
|------|---------|
| {file} | {purpose} |

Convention Analysis

## Detected Conventions

### Confirmed Patterns
- {Pattern}: {evidence} (found in X% of files)

### Inconsistencies
⚠️ {Pattern}: {variant1} ({X%}) vs {variant2} ({Y%})
   Recommendation: Standardize on {recommended}

Monorepo Analysis

For monorepos (pnpm workspaces, yarn workspaces, nx, turborepo):

## Monorepo Structure

### Workspace Configuration
- Tool: {pnpm/yarn/npm/nx/turborepo}
- Config: {workspace config file}

### Packages
| Package | Type | Dependencies |
|---------|------|--------------|
| {name} | {lib/app} | {internal deps} |

### Build Order
1. {package1} (no deps)
2. {package2} (depends on 1)
3. {package3} (depends on 1, 2)

### Shared Configuration
- TypeScript: {shared tsconfig}
- Testing: {shared test config}
- Linting: {shared lint config}

Error Patterns to Flag

## Issues Detected

### Critical
❌ {issue}: {description}
   Location: {file:line}
   Impact: {impact}

### Warning
⚠️ {issue}: {description}
   Location: {file:line}
   Recommendation: {fix}

### Info
ℹ️ {observation}

Integration with Steering Workflow

When used during /steering:

1. Phase 2 uses this skill for systematic codebase exploration
2. Product track extracts README and documentation
3. Tech track discovers dependencies and build tools
4. Structure track maps directories and patterns
5. Convention track identifies code style rules

Best Practices

1. Sample Strategically: Don't read every file; pick representative samples
2. Parallel Execution: Run independent analyses concurrently
3. Evidence-Based: Document where patterns were observed
4. Mark Uncertainty: Use ⚠️ for unclear or conflicting patterns
5. Actionable Output: Focus on patterns AI agents need to follow