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---
name: duplicate-finder
description: Finds duplicated logic across the codebase and proposes shared abstractions
argument-hint: [directory]
user-invocable: true
allowed-tools: Bash Grep Read
effort: medium
---
## Find Duplicate Code
1. Look for structural duplication:
```bash
# Similar function signatures
grep -rn "async function\|const .* = async" ${1:-src}/ --include="*.ts" | sort | head -40
# Similar patterns (fetch calls, error handling, etc.)
grep -rn "try {" ${1:-src}/ --include="*.ts" -l
```
2. Read suspected duplicate files side by side.
3. Identify duplication categories:
- **Identical blocks**: copy-pasted code
- **Near-duplicates**: same logic, different variable names
- **Structural similarity**: same pattern, different implementations
4. For each duplication cluster:
- Show the duplicated sections
- Propose a shared abstraction (utility function, custom hook, base class)
- Show how call sites would look after extraction
5. Ask which ones to consolidate, then apply.
Focus on impactful duplications (3+ occurrences or > 20 lines).
