What problem does it solve? Codebases accumulate unnecessary complexity: hand-rolled utilities that duplicate the standard library, speculative abstractions with a single implementation, and dependencies that add nothing. This Skill reviews diffs exclusively for over-engineering and reports exactly what to cut, one line per finding. ## Core Features & Use Cases - Complexity-Only Review: Hunts dead code, reinvented standard library functions, unneeded dependencies, and speculative abstractions while ignoring correctness, security, and performance issues. - Tagged One-Line Findings: Each finding uses a tag (delete, stdlib, native, yagni, shrink) with the location, what to cut, and what replaces it. - Net-Line Scoring: Ends every review with a net line-reduction estimate, or reports "Lean already. Ship." when nothing can be cut. - Use Case: After opening a pull request, ask for an over-engineering review to discover that a 27-line validator class can be replaced by a one-line standard library call before merging. ## Quick Start Review this diff for over-engineering and tell me what can be deleted or replaced with standard library equivalents.