@fallow-rs/fallow

Codebase intelligence for JavaScript and TypeScript. Free static layer finds unused code (files, exports, types, dependencies), code duplication, circular dependencies, complexity hotspots, architecture boundary violations, and feature flag patterns. Runtime coverage merges production execution data into the same health report for hot-path review, cold-path deletion confidence, and stale-flag evidence - a single local capture is free, while continuous/cloud runtime monitoring is paid. 95 framework plugins, zero configuration, sub-second static analysis. Use when asked to analyze code health, find unused code, detect duplicates, check circular dependencies, audit complexity, check architecture boundaries, detect feature flags, clean up the codebase, auto-fix issues, merge runtime coverage, or run fallow.

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SKILL.md
<p align="center">
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  <strong>Agent skills for the fallow codebase intelligence layer for TypeScript and JavaScript.</strong><br><br>
  <a href="https://opensource.org/licenses/MIT"><img src="https://img.shields.io/badge/License-MIT-blue.svg" alt="MIT License"></a>
  <a href="https://github.com/fallow-rs/fallow-skills/actions/workflows/validate.yml"><img src="https://github.com/fallow-rs/fallow-skills/actions/workflows/validate.yml/badge.svg" alt="CI"></a>
  <a href="https://agentskills.io"><img src="https://img.shields.io/badge/Agent_Skills-compatible-8A2BE2" alt="Agent Skills"></a>
  <a href="https://github.com/fallow-rs/fallow"><img src="https://img.shields.io/badge/fallow-v3.9.0-orange" alt="fallow v3.9.0"></a>
</p>

Agent skills for fallow, codebase intelligence for TypeScript and JavaScript. The static layer reports quality, changed-code risk, cleanup opportunities, circular dependencies, code duplication, complexity hotspots, architecture boundary violations, and design-system styling drift in milliseconds. Optional runtime intelligence adds production execution evidence so agents can delete cold code, flag hot-path changes, and retire stale flags with proof. 123 framework plugins, zero configuration. Works with any agent that supports the Agent Skills specification: Claude Code, Cursor, OpenAI Codex, Windsurf, GitHub Copilot, Gemini CLI, Amp, and 30+ more. See Fallow for coding agents for the visual overview and store links.

Linters enforce style. Formatters enforce consistency. Fallow enforces relevance. Linters work file by file. TypeScript works type by type. Neither builds the full module graph, so neither can see what nothing depends on. Fallow does, in milliseconds. These skills teach agents how to use fallow effectively: which commands to run, what flags to use, how to interpret output, and how to avoid common pitfalls.

Quick Start

Agent Skills CLI

npx skills add fallow-rs/fallow-skills

Claude Code

/plugin marketplace add fallow-rs/fallow-skills
/plugin install fallow@fallow-skills

OpenAI Codex

codex plugin marketplace add fallow-rs/fallow-skills
codex plugin add fallow@fallow-skills

Fallow Impact statusline

Fallow Impact can show the latest whole-project issue count, the comparable trend, and everything cleared while tracking:

fallow impact  7 issues in last full scan · 5 fewer than prior · 4.9k cleared while tracking

Claude Code users can add the compact branded segment while preserving an existing command-based statusline:

/fallow:impact-statusline setup user compose

Use project instead of user for private project-local configuration. The setup previews the exact line before it changes settings, stores the previous value for safe removal, and never enables Impact. Run /fallow:impact-statusline remove user to restore the previous setting.

Codex and other agents can use the same stable local surface directly:

fallow impact statusline

Agent-specific CLI shortcuts

npx skills add fallow-rs/fallow-skills --agent windsurf
npx skills add fallow-rs/fallow-skills --agent amp
gemini skills install https://github.com/fallow-rs/fallow-skills.git

Manual install

tmp=$(mktemp -d)
git clone https://github.com/fallow-rs/fallow-skills.git "$tmp/fallow-skills"

Copy both skill directories into your agent's skills folder:

# OpenAI Codex, Amp, and agents using the shared Agent Skills location
mkdir -p ~/.agents/skills
cp -R "$tmp/fallow-skills/fallow/skills/." ~/.agents/skills/

# Claude Code
mkdir -p ~/.claude/skills
cp -R "$tmp/fallow-skills/fallow/skills/." ~/.claude/skills/

# Cursor
mkdir -p ~/.cursor/skills
cp -R "$tmp/fallow-skills/fallow/skills/." ~/.cursor/skills/

# Windsurf
mkdir -p ~/.codeium/windsurf/skills
cp -R "$tmp/fallow-skills/fallow/skills/." ~/.codeium/windsurf/skills/

# GitHub Copilot
mkdir -p .github/skills
cp -R "$tmp/fallow-skills/fallow/skills/." .github/skills/
<details>
<summary>Other agents</summary>

Use npx skills add fallow-rs/fallow-skills --all for installer-managed discovery, or copy the directories under fallow/skills/ into your agent's skills location. These skills follow the open Agent Skills specification and work with any compatible agent.

</details>

Prerequisites

Fallow must be installed in the target project:

npm install -g fallow    # prebuilt binaries
npx fallow                   # or run without installing

See the installation guide for all options including cargo install fallow-cli.

Available Skills

Skill Description Trigger phrases
fallow Codebase intelligence for JS and TS, code and styles: quality, changed-code risk, cleanup opportunities, circular deps, duplication, complexity, design-system drift, and runtime evidence "check code health", "audit this PR", "find cleanup opportunities", "find duplicates", "what code actually runs"
fallow-review Graph-grounded review of changed-code risk, blast radius, and consequential structural decisions "review this branch", "review this PR", "check changed code before merge"

What's Included

This repository contains portable skills for users of the released product. Fallow's maintainer workflows stay in the main source repository, and public user documentation stays in fallow-rs/docs.

fallow

Category What it does
Cleanup Find unused files, exports, types, dependencies, enum/class members, stale suppressions, and other safe cleanup candidates
Duplication Find code clones with 4 modes: strict, mild, weak, semantic
Complexity Function complexity analysis, hotspot detection, health scores
Auto-Fix Remove unused exports and dependencies with dry-run preview
CI GitHub Actions, SARIF upload, baseline comparison, PR-scoped checks
Monorepo Per-workspace analysis with cross-package resolution
Debug Trace export usage chains, file edges, and dependency usage

fallow-review

Reviews a branch or pull request with fallow's graph-grounded review brief. It subtracts deterministic findings, focuses attention by blast radius and risk, and frames consequential structural decisions for human judgment.

Reference Documentation

  • CLI Reference: all commands, flags, JSON output structure, config format
  • Gotchas: common pitfalls with WRONG/CORRECT examples
  • Patterns: workflow recipes for CI, monorepos, migration, and incremental adoption

Example Prompts

Once installed, you can use natural language:

  • "Audit the codebase quality"
  • "Are there any unused dependencies?"
  • "Find code duplication in the codebase"
  • "Clean up unused exports"
  • "Set up a CI quality gate"
  • "Check the complexity of this codebase"
  • "Why is this export flagged as unused?"
  • "Check if this PR introduces quality risk"
  • "Find unused files in the payments package"
  • "What's the duplication percentage?"

How It Works

User: "Find all unused exports"
  ↓
Agent loads fallow skill
  ↓
Skill instructs: run `fallow dead-code --format json --quiet --unused-exports`
  ↓
Agent executes command, parses JSON output
  ↓
Agent summarizes findings with file paths and line numbers

The skill provides agents with:

  1. Command knowledge: which fallow command + flags to use for each task
  2. Output parsing: how to interpret JSON results
  3. Guardrails: always dry-run before fix, never run watch, use --yes in non-TTY
  4. Debugging: how to trace false positives with --trace

Contributing

See AGENTS.md for repository structure and quality standards. source-lock.json pins the public Fallow contract used by the fallow skill. CI checks that pin against a clean source checkout and rejects contract or privacy-boundary drift. Maintainers can find the versioning, packaging, and store update procedure in RELEASING.md.

Related

License

MIT. See LICENSE for details.

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