Code Deduplication Skill Purpose: Prevent semantic duplication and code bloat. Maintain a capability index so Claude always knows what exists before writing something new. Core Philosophy Code Index Structure Maintain CODE INDEX.md in project root, organized by capability not file location: File Header Format Every file should have a summary header: TypeScript/JavaScript Python Function Documentation Every function needs a one line summary: TypeScript Python Check Before Write Process Before Creating ANY New Function Decision Tree Common Duplication Patterns Pattern 1: Utility Function Reimplementation ❌ Bad: Creating validateEmail() when isEmail() exists ✅ Good: Check index first, use existing Pattern 2: Slightly Different Versions ❌ Bad: Multiple date formatters with slight variations ✅ Good: One function with options Pattern 3: Inline Logic That Should Be Extracted ❌ Bad: Same validation logic scattered across files ✅ Good: Extract once, import everywhere Periodic Audit Run /audit duplicates periodically to catch semantic overlap: Audit Checklist [ ] Utility functions : Any functions doing similar things? [ ] API calls : Multiple ways to fetch same data? [ ] Validation : Scattered inline validation logic? [ ] Error handling : Inconsistent error patterns? [ ] Components : Similar UI components that could merge? [ ] Hooks : Custom hooks with overlapping logic? Audit Output Format Vector DB Integration (Optional) For large codebases (100+ files), add vector search: Setup with ChromaDB Setup with LanceDB (Lighter) When to Use Vector DB Codebase Size Recommendation < 50 files Markdown index only 50 200 files Markdown + periodic audit 200+ files Add vector DB 500+ files Vector DB essential Claude Instructions At Session Start 1. Read CODE INDEX.md if it exists 2. Note the categories and key functions available 3. Keep this context for the session Before Writing New Code 1. Pause and check : "Does something like this exist?" 2. Search CODE INDEX.md for similar capabilities 3. If unsure, search the codebase: grep r "functionName\ similar term" src/ 4. Only create new if confirmed nothing suitable exists After Writing New Code 1. Immediately update CODE INDEX.md 2. Add file header if new file 3. Add function docstring 4. Commit index update with code When User Says "Add X functionality" Quick Reference Update Index Command Audit Command File Header Template Function Template Index Entry Template

code-deduplication