Review Duplication

This is a code review workflow that makes Claude hunt down duplicate code and reinvented wheels before you merge. It walks through extracting core logic from a PR, hypothesizing where similar code already lives in your repo, then delegating deep codebase searches to sub-agents that look for structural similarities, naming patterns, and architectural fit. The real value is in step 5, where it teaches Claude to write constructive feedback with actual file paths and refactoring snippets, not just "this looks duplicated." It's thorough but heavy, best for teams that keep shipping the same date formatter in six different files because nobody checks what's already in utils.

skills.sh installs: 352
GitHub stars: 108.7K
last updated: Aug 21, 2026

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Install

$ npx -y skills add google-gemini/gemini-cli --skill review-duplication --agent claude-code

Installs into .claude/skills of the current project.

Files

Review Duplication

Overview

This skill provides a structured workflow for investigating a codebase during a code review to identify duplicated logic, reinvented utilities, and missed opportunities to reuse established patterns. By executing this workflow, you ensure that new code integrates seamlessly with the existing project architecture.

Workflow: Investigating for Duplication

When reviewing code, perform the following steps before finalizing your review:

1. Extract Core Logic

Analyze the new code to identify the core algorithms, utility functions, generic data structures, or UI components being introduced. Look beyond the specific business logic to see the underlying mechanics.

SKILL.md on GitHub

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