fallow

fallow is a skill for Claude Code from ensemblr-hq/ensemblr. It costs 178 tokens per session (9,009 once invoked), scanned C, a copy of fallow, Apache-2.0.

A static-analysis tool for JavaScript and TypeScript codebases. It reports code quality, duplication, dependency problems, circular imports, complex areas, architecture-boundary violations, feature-flag patterns, and selected security candidates; it can also combine these findings with runtime coverage data.

In plain words
What is it for?
Use it to inspect a JavaScript or TypeScript project before a release or refactor, find duplicated or unused code, identify complex or poorly separated areas, and set quality or duplication checks in continuous integration.
Why use it?
It shows where a codebase is difficult to maintain or contains cleanup opportunities, including files, exports, types, or dependencies that may no longer be used. This gives teams evidence for cleanup, refactoring, and CI checks.

Skill for Claude Code

Written for Claude Code: $ARGUMENTS substitution. Also seen: installed under .agents/ (shared by several agents); mentions Codex; built for cline.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/ensemblr-hq/ensemblr/fallow
Any agent
npx skills add ensemblr-hq/ensemblr --skill fallow
Clone the repo
git clone --depth 1 https://github.com/ensemblr-hq/ensemblr

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

README.md
[![agentmods](https://agentmods.dev/badge/skills/ensemblr-hq/ensemblr/fallow.svg)](https://agentmods.dev/skills/ensemblr-hq/ensemblr/fallow)
Your own site
<a href="https://agentmods.dev/skills/ensemblr-hq/ensemblr/fallow"><img src="https://agentmods.dev/badge/skills/ensemblr-hq/ensemblr/fallow.svg" alt="Measured on agentmods" height="20"></a>
Per session 178 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 9,009 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. Scan, not verified.
Origin 86% copy Near-identical to another mod 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 $0.00178 $0.09009
Opus 5 $0.00089 $0.04505
Sonnet 5 $0.00036 $0.01802
Haiku 4.5 $0.00018 $0.00901

Measured 6d ago against content hash 7d48d4e64f7e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade C, and why

fallow scanned grade C with 1 finding 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 6d 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.

Hidden instructionshighPrompt injection

Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.

| `health` | Function complexity analysis (also covers Angular templates as synthetic `<template>` findings: external `.html` files via `templateUrl` AND inline `@Component({ template: \`...\` })` literals; suppress exte
Origin

This is a copy

86% identical to fallow — 493 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/fallow/SKILL.md · 410 lines

How it starts

The opening of the file, as written. The whole thing — 410 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fallow: codebase intelligence for JavaScript and TypeScript

Codebase intelligence for JavaScript and TypeScript. The free static layer reports quality, changed-code risk, cleanup opportunities, circular dependencies, code duplication, complexity hotspots, architecture boundary violations, feature flag patterns, and opt-in security candidates. Runtime coverage merges production execution data into the same fallow health report for hot-path review, cold-path deletion confidence, and stale-flag evidence, with a single local capture available by default and continuous/cloud runtime monitoring available as an optional mode. 118 framework plugins, zero configuration, sub-second static analysis.

When to Use

  • Finding cleanup opportunities (unused files, exports, types, enum/class members)
  • Finding unused or unlisted dependencies
  • Detecting code duplication and clones
  • Checking code health and complexity hotspots
  • Cleaning up a codebase before a release or refactor
  • Auditing a project for structural issues
  • Setting up CI quality gates or duplication thresholds
  • Auto-fixing unused exports and dependencies
  • Detecting feature flag patterns (environment gates, SDK calls, config objects)
  • Investigating why a specific export or file appears unused

When NOT to Use

  • Runtime error analysis or debugging
  • Type checking (use tsc for that)
  • Linting style or formatting issues (use ESLint, Biome, Prettier)
  • Verified security vulnerability scanning or SAST. fallow security surfaces local, deterministic security candidates for a downstream agent to verify; it does not prove exploitability. Use Snyk, CodeQL, or Semgrep for verified scanning, and an SCA tool for dependency CVEs.
  • Bundle size analysis
  • Projects that are not JavaScript or TypeScript

Prerequisites

Fallow must be installed. If not available, install it:

npm install -g fallow          # prebuilt binaries (fastest)
# or
npx fallow dead-code               # run without installing
# or
cargo install fallow-cli        # build from source

Read the full file on GitHub · 410 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. 6d ago First seen · 410 lines · 178 tokens per session scan C 7d48d4e64f7e

Subscribe to this mod's changes

fallow is a skill published in the GitHub repository ensemblr-hq/ensemblr (7 stars, last pushed yesterday), licensed Apache-2.0. It adds 178 tokens to every session and 9,009 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it C with 1 finding (hidden instructions). It is 86% identical to fallow, differing in 493 lines, and is treated as a copy.

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