biome

biome is a skill for Claude Code from moabualruz/fulcrum. It costs 65 tokens per session (212 once invoked), scanned A, a copy of bat, MIT.

A code formatter and checker for JavaScript, TypeScript, JSON, CSS, HTML, and several related formats. It can apply consistent formatting and report code-quality problems from one configuration.

In plain words
What is it for?
Use it to format or check JavaScript, TypeScript, JSX, TSX, JSON, JSONC, CSS, GraphQL, HTML, Vue, Svelte, or Astro files.
Why use it?
It removes the need to manage separate tools for formatting and linting, where linting means finding likely mistakes or unwanted code patterns. A shared setup makes code style more consistent.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the fulcrum plugin — 32 skills shipped together

Good fit Use it to format or check JavaScript, TypeScript, JSX, TSX, JSON, JSONC, CSS, GraphQL, HTML, Vue, Svelte, or Astro files.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/moabualruz/fulcrum/biome
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.

Any agent
npx skills add moabualruz/fulcrum --skill biome
Clone the repo
git clone --depth 1 https://github.com/moabualruz/fulcrum

Made for: Claude Code.

Or install fulcrum, the plugin that ships this one along with the rest of its 32 skills.

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 biome

README.md
[![agentmods](https://agentmods.dev/badge/skills/moabualruz/fulcrum/biome/github.svg)](https://agentmods.dev/skills/moabualruz/fulcrum/biome)
Your own site
<a href="https://agentmods.dev/skills/moabualruz/fulcrum/biome"><img src="https://agentmods.dev/badge/skills/moabualruz/fulcrum/biome/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 biome

Your own site · 80×15
<a href="https://agentmods.dev/skills/moabualruz/fulcrum/biome"><img src="https://agentmods.dev/badge/skills/moabualruz/fulcrum/biome.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 65 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 212 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 78% 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 $0.00065 $0.00212
Opus 5 $0.00032 $0.00106
Sonnet 5 $0.00013 $0.00042
Haiku 4.5 $0.00006 $0.00021

Measured 10d ago against content hash d2581547ba68, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

biome 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 10d 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

This is a copy

78% identical to bat — 6 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.

plugins/fulcrum/skills/biome/SKILL.md · 28 lines

What it actually says

biome

When to use

See references/when-to-use.md. Load only when this section is needed.

Invocation

See references/invocation.md. Load only when this section is needed.

Patterns

See references/patterns.md. Load only when this section is needed.

Anti-patterns

See references/anti-patterns.md. Load only when this section is needed.

Cross-refs

See references/cross-refs.md. Load only when this section is needed.

Files

What ships with it

5 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. 10d ago First seen · 28 lines · 65 tokens per session scan A d2581547ba68

Subscribe to this mod's changes

biome is a skill published in the GitHub repository moabualruz/fulcrum (3 stars, last pushed 2mo ago), licensed MIT. It adds 65 tokens to every session and 212 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 78% identical to bat, differing in 6 lines, and is treated as a copy.

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