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.
npx skills add https://github.com/google-gemini/gemini-cli --skill review-duplication