finding-duplicate-functions

name	finding-duplicate-functions
description	Use when auditing a codebase for semantic duplication — functions that do the same thing but have different names or implementations, especially common in LLM-generated codebases
when_to_use	after syntactic duplicate detection (jscpd), during codebase audits, or before major refactoring to find consolidation opportunities
version	1.0.0
category	debugging
author	Jesse Vincent
license	MIT
source	https://github.com/obra/superpowers-lab/tree/main/skills/finding-duplicate-functions
tags	["debugging","refactoring","duplication","code-quality","analysis"]
effort	medium

Finding Duplicate-Intent Functions

Overview

LLM-generated codebases accumulate semantic duplicates: functions that serve the same purpose but were implemented independently. Classical copy-paste detectors (jscpd) find syntactic duplicates but miss "same intent, different implementation."

This skill uses a two-phase approach: classical extraction followed by LLM-powered intent clustering.

When to Use

• Codebase has grown organically with multiple contributors (human or LLM)
• You suspect utility functions have been reimplemented multiple times
• Before major refactoring to identify consolidation opportunities
• After jscpd has been run and syntactic duplicates are already handled

Quick Reference

Phase	Tool	Model	Output
1. Extract	Extract function catalog	-	catalog.json
2. Categorize	Categorize by domain	haiku model	categorized.json
3. Split	Split by category	-	categories/*.json
4. Detect	Find duplicates per category	opus model	duplicates/*.json
5. Report	Generate prioritized report	-	report.md

Process

Phase 1: Extract Function Catalog

Extract all functions from source files. Focus on:

• Exported functions and public methods
• Files in utility/helper directories
• Excluding test files (*.test.*, *.spec.*, __tests__/**)

For each function capture:

• Function name and signature
• File path and location
• ~15 lines of context (enough to understand intent)

Phase 2: Categorize by Domain

Dispatch a haiku subagent to categorize functions by domain.

Insert the function catalog into the prompt. Save output as categorized.json with functions grouped into domains like:

• String manipulation
• Validation
• Path operations