fallow

fallow-rs/fallow is an open-source project by fallow-rs: Codebase intelligence for TypeScript and JavaScript. Free static analysis of code and styles: unused code, duplication, circular deps, complexity hotspots, architecture boundaries, design-system drift. Optional paid runtime layer (Fallow Runtime): hot-path review and cold-path deletion evidence from real production traffic.. Indexed here so it can be found — not resold.

It is free. Get it from the upstream repository: https://github.com/fallow-rs/fallow

From the project's own README (excerpt, reproduced for discovery under its MIT license):

Codebase intelligence for TypeScript and JavaScript. One binary finds unused code, circular dependencies, duplication, complexity hotspots, boundary violations, and design-system styling drift. An optional paid layer, Fallow Runtime, adds production execution evidence. Deterministic findings and typed output contracts. No AI inside the analyzer, and no TypeScript compiler or Node.js runtime needed for static analysis.

Docs · Quickstart · MCP · Benchmarks

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Most repositories carry code nobody dares to delete, because deleting means proving a negative: fallow reads the repository as one dependency graph, from import edges to styling tokens, and reports what that graph shows.

Excerpt from fallow audit on the vitest monorepo, auditing its last 15 commits. fallow 3.5.0, warm base-snapshot cache. The gate passed: the 163 inherited findings are pre-existing and excluded by design, so they do not block the change. The same run with --format json returns one typed JSON document.

Quick start

The npm package ships the fallow, fallow-lsp, and fallow-mcp launchers plus a version-matched agent skill, so the editor and agent integrations resolve the project-local binary instead of whatever happens to be on PATH. Runs are deterministic: the same input produces the same output with stable fingerprints. Re-running to verify an edit is safe. Other channels (pnpm, yarn, cargo install fallow-cli, and a local Docker build with a Compose example at examples/docker/compose.yaml) are covered in the installation guide.

What fallow reports • Unused files, exports, types, enum and class members, and dependencies • Circular dependencies and re-export cycles, part of fallow dead-code • Code duplication with a suffix-array detector covering JS/TS and…