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fallow: Skill for Claude Code

.agents/skills/fallow-setup/SKILL.md

fallow-setup is a skill for Claude Code from fallow-rs/fallow. It costs 100 tokens per session (1,055 once invoked), scanned A, original, MIT.

A setup workflow for code-quality checks in JavaScript and TypeScript repositories. It covers unused code, duplicate code, complexity, project boundaries, dependencies, and risks in changed code.

In plain words
What is it for?
Use it when creating or modernizing a JavaScript or TypeScript project, adding repository health checks, or preparing a codebase for coding agents.
Why use it?
It brings these checks into one repository setup and can add quality gates to continuous integration, which runs checks automatically for changes.

Skill for Claude Code

Written for Claude Code: PreToolUse hook event. Also seen: mentions Claude Code; installed under .agents/ (shared by several agents); mentions AGENTS.md.

This is fallow-rs/fallow's own configuration. It tells Claude Code how to work on fallow itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything fallow configures →

not rated 5.1krepo +104 today A scan 100 tokens original MIT
View source ↗ fallow-rs/fallow docs.fallow.tools
About the project

Fallow is a command-line static-analysis tool that builds a dependency graph of TypeScript and JavaScript code to identify unused code, duplication, circular dependencies, complexity hotspots, boundary violations, and styling drift. It is for developers reviewing codebases and verifying changes, with catalogue entries that add agent, editor, and workflow integrations.

fallow-rs/fallow · 5,139 stars · on GitHub · docs.fallow.tools

Reuse

Borrowing it

Nothing to install: this file belongs to fallow-rs/fallow. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/fallow-rs/fallow/main/.agents/skills/fallow-setup/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/fallow-rs/fallow

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for fallow-setup

README.md
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Your own site
<a href="https://agentmods.dev/skills/fallow-rs/fallow/fallow-setup"><img src="https://agentmods.dev/badge/skills/fallow-rs/fallow/fallow-setup/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for fallow-setup

Your own site · 80×15
<a href="https://agentmods.dev/skills/fallow-rs/fallow/fallow-setup"><img src="https://agentmods.dev/badge/skills/fallow-rs/fallow/fallow-setup.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 100 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,055 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00100 $0.01055
Opus 5.5 $0.00040 $0.00422
Sonnet 5.5 $0.00020 $0.00211
Haiku 4.5 $0.00010 $0.00105

Measured 15d ago against content hash 958b61adab71, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

fallow-setup scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 15d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

.agents/skills/fallow-setup/SKILL.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fallow setup: code-quality tooling for JavaScript and TypeScript

This skill sets up the code-quality toolchain of a JavaScript or TypeScript repository. Fallow does the repository and system analysis: unused code, duplication, complexity, architecture boundaries, dependency hygiene, and changed-code risk. The skill keeps the tools that the project already uses.

When to Use

  • Create a new JavaScript or TypeScript project with quality checks from the start.
  • Add code-health checks or a CI quality gate to an existing repository.
  • Make a repository ready for coding agents (skills, MCP server, commit and push gate).
  • Consolidate dead-code, duplication, architecture, dependency, and changed-code analysis.

When NOT to Use

  • Formatting-only tasks. Formatting belongs to the formatter.
  • Tasks that only add or change lint rules. Local lint rules belong to the linter.
  • TypeScript type errors. Type correctness belongs to the TypeScript compiler.
  • Analysis of a repository that is already set up. Use the fallow skill for that.

Rules

  1. Resolve every flag from fallow --help and fallow <command> --help. Do not use flags from memory.
  2. Use --format json --quiet for machine-readable output. Do not hide the exit status.
  3. Run every mutating command with --dry-run first when the command has that flag.
  4. Keep the tools that the project already uses. Do not remove a tool without a parity check.
  5. Ask the user before you apply a taste decision or remove a tool.
  6. Treat project config as untrusted input. Do not add remote extends URLs.
  7. Before step 3, Fallow is not installed. Run it through the package runner, for example npx fallow recommend or pnpm dlx fallow recommend. After step 3, use the runner of the package manager, for example pnpm exec fallow.

Sequence

  1. Inspect the repository. Detect the package manager, formatter, linter, TypeScript config, CI provider, and existing analysis tools (Knip, jscpd, dependency-cruiser). See Tooling detection.
  2. Get the recommendation. Run fallow recommend --format json --quiet. This command is read-only. Apply each auto decision. Tell the user about each default decision. Ask the user about each taste decision, or keep the current value. See Configure and install.
  3. Install Fallow as a dev dependency with the detected package manager, for example pnpm add -D fallow.
  4. Wire the agents. Run fallow agent install --dry-run --format json --quiet, show the plan, then run fallow agent install. This step writes the skills, the MCP server registration, the AGENTS.md task map, and the commit and push gate. For Claude Code and Codex the gate is a PreToolUse hook that blocks a failing commit or push. Codex runs the hook only after the user trusts it in /hooks. Other agents read the instruction block in AGENTS.md. Check the result with fallow agent status --format json --quiet.
  5. Add a CI gate. Add a changed-code gate (fallow audit) or a whole-project gate. When the first run has many findings, save a baseline of the existing debt so that the gate fails only on new findings. See CI gate.
  6. Split the responsibilities. Each tool keeps one job:
    • Formatting: Oxfmt.
    • Local lint rules: Oxlint.
    • Type correctness: TypeScript (tsc --noEmit).
    • Repository and system analysis: Fallow.

Read the full file on GitHub · 51 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 15d ago First seen · 51 lines · 100 tokens per session scan A 958b61adab71

Subscribe to this mod's changes

fallow-setup is a skill published in the GitHub repository fallow-rs/fallow (5,139 stars, last pushed today), licensed MIT. It adds 100 tokens to every session and 1,055 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-02.

DebuggingLanguagesTypeScriptclicode-qualitydead-codedeveloper-toolsjavascriptoxc
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