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Agent skill

Biome

by managedcode in managedcode/dotnet-skills

Use Biome in .NET repositories that ship Node-based frontend assets and want a fast combined formatter-linter-import organizer for JavaScript, TypeScript, CSS, JSON, GraphQL, or HTML.

MITAuto-check passedDevelopment

Install Biome

skills CLI
$ npx skills add managedcode/dotnet-skills --skill biome -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install managedcode/dotnet-skills biome --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/managedcode/dotnet-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/catalog/Tools/Biome/skills/biome .claude/skills/biome && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
biome
GitHub stars
486
Token cost
~1.7k tokens
SKILL.md length
822 words
Files
2
Skills in repo
81
Repo updated
First seen
Licence
MIT

At a glance

Use Biome in .NET repositories that ship Node-based frontend assets and want a fast combined formatter-linter-import organizer for JavaScript, TypeScript, CSS, JSON, GraphQL, or HTML.

  • Works in 7 steps: Decide ownership first → Prefer a repo-local pinned install so CI… → Generate biome.json only after… → …
  • @biomejs/biome setup
  • SKILL.md covers Trigger On, Do Not Use For, Inputs and Workflow, plus 7 more sections
  • Calls npx, rg and npm

What it does

Biome is an agent skill from managedcode/dotnet-skills. Use Biome in .NET repositories that ship Node-based frontend assets and want a fast combined formatter-linter-import organizer for JavaScript, TypeScript, CSS, JSON, GraphQL, or HTML. USE FOR: biome.json or @biomejs/biome setup; fast frontend formatting and linting; replacing overlapping frontend style tools deliberately. DO NOT USE FOR: ESLint-only plugin coverage; runtime site audits such as headers, accessibility, or browser behavior. INVOKES: inspect the repository context, edit targeted files, and run…

Its SKILL.md is about 1.7k tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file (for example `manifest.json`). Compatibility notes: Requires a .NET repository with frontend assets managed through Node or a standalone Biome binary workflow; keep ownership explicit versus ESLint, Stylelint…

It sits in Development, covering Linting and formatting. It works with ESLint, .NET, GraphQL and JavaScript. The repository describes itself as: Installable .NET skill catalog and CLI for Codex, Claude Code, GitHub Copilot, and Gemini. The licence is MIT.

When your agent uses it

  • @biomejs/biome setup
  • Fast frontend formatting and linting
  • Replacing overlapping frontend style tools deliberately
  • : ESLint-only plugin coverage

Example prompts

  • “/biome”

Requirements

  • Node.js
  • Compatibility (from SKILL.md): Requires a .NET repository with frontend assets managed through Node or a standalone Biome binary workflow; keep ownership explicit versus ESLint, Stylelint, and webhint.

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

  1. Decide ownership first
  2. Prefer a repo-local pinned install so CI and developer machines use the same version.
  3. Generate biome.json only after confirming what the repo wants Biome to own.
  4. Add repeatable scripts to package.json, for example
  5. Keep file ownership explicit
  6. Start migrations with check and bounded folders before flipping the whole repo to --write.
  7. Re-run the frontend build and tests after broad formatting or lint-fix passes.

What it can do on your machine

Read from SKILL.md and the folder at commit 535dd55. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • npx
    • rg
    • npm

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Requires a .NET repository with frontend assets managed through Node or a standalone Biome binary workflow; keep ownership explicit versus ESLint, Stylelint, and webhint.

    From compatibility in the SKILL.md frontmatter.

Context cost

Biome loads about 1.7k tokens when it runs. Until then it costs about 148 tokens; SKILL.md has 822 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~148
When it runs · the whole SKILL.md, loaded when a task matches
~1.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from managedcode/dotnet-skills at commit 535dd55, republished under its MIT licence (© managedcode). 822 words, ~1,749 tokens.

Download SKILL.mdSave it as .claude/skills/biome/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
biome
description
Use Biome in .NET repositories that ship Node-based frontend assets and want a fast combined formatter-linter-import organizer for JavaScript, TypeScript, CSS, JSON, GraphQL, or HTML. USE FOR: biome.json or @biomejs/biome setup; fast frontend formatting and linting; replacing overlapping frontend style tools deliberately. DO NOT USE FOR: ESLint-only plugin coverage; runtime site audits such as headers, accessibility, or browser behavior. INVOKES: inspect the repository context, edit targeted files, and run relevant build, test, lint, or validation commands when changes are made.
compatibility
Requires a .NET repository with frontend assets managed through Node or a standalone Biome binary workflow; keep ownership explicit versus ESLint, Stylelint, and webhint.

Biome for Frontend Assets in .NET Repositories

Trigger On

  • the repo has biome.json, @biomejs/biome, or the user asks for a faster all-in-one frontend formatter-linter stack
  • the repo wants one tool for formatting, linting, and import organization across JS, TS, CSS, JSON, GraphQL, or HTML
  • the team is comparing Biome against ESLint plus Prettier or wants to simplify the current stack

Do Not Use For

  • repos that rely on ESLint plugins or framework-specific rules Biome does not cover yet
  • runtime site audits such as headers, accessibility, and SEO; route that to webhint
  • cases where a dedicated CSS or HTML tool is still the deliberate owner and no migration is requested

Inputs

  • the nearest AGENTS.md
  • package.json
  • biome.json or biome.jsonc
  • current ownership across ESLint, Prettier, Stylelint, and import ordering

Workflow

  1. Decide ownership first:
    • Biome as the main formatter and linter
    • Biome only for formatting
    • Biome in coexistence with ESLint for plugin gaps
  2. Prefer a repo-local pinned install so CI and developer machines use the same version.
  3. Generate biome.json only after confirming what the repo wants Biome to own.
  4. Add repeatable scripts to package.json, for example:
    • biome check .
    • biome check . --write
  5. Keep file ownership explicit:
    • Biome can own formatting, linting, and import sorting
    • webhint still owns site-runtime audits
    • ESLint may stay for plugin-heavy cases the repo intentionally keeps
  6. Start migrations with check and bounded folders before flipping the whole repo to --write.
  7. Re-run the frontend build and tests after broad formatting or lint-fix passes.

Current Upstream Notes

  • Biome CLI 2.5.12 fixes Astro expression parsing, nested JSX attribute sorting, Unicode stdin/stdout corruption, and repeated dependency scanning. Validate representative Astro/TSX files, Unicode input, and formatter idempotence before dropping workarounds.

  • noFloatingPromises now handles cyclic imports and awaited Promise aliases more accurately; awaiting an array of Promises still leaves its elements unhandled. Use Promise.all or an explicit awaited loop when appropriate. New Nursery rules remain opt-in, including useFlatMathMinMax, useModernMathApis, noThisOutsideOfClass, noVueDeprecatedScopedSlots, and noBunModules.

  • Biome CLI 2.5.11 includes the 2.5.8-2.5.10 rule and parser additions and adds Nursery rules for unsafe Astro set:html and undeclared CSS custom properties. Enable Nursery rules explicitly; do not treat a version update as permission to change the repository's lint policy.

  • The release fixes Astro shorthand anchors, implicit fragments, void elements, and full HTML handling through --stdin-file-path; Vue template/CSS binding false positives; GraphQL naming trivia; and several type-inference performance paths. Re-run the repository's existing biome check and formatter-idempotence tests before removing suppressions or accepting churn.

  • When --stdin-file-path is used, verify that the intended nested biome.json is selected and that ignored input produces the expected warning. Keep fixtures for Vue custom blocks, Svelte attachments, Tailwind class sorting, and non-ASCII diagnostic spans when those surfaces matter.

  • Recent Biome changes also continue expanding CSS/SCSS, HTML accessibility, import sorting, watch mode, and upgrade-command surfaces; verify actual CLI ownership before replacing ESLint or Stylelint.

Show full SKILL.md (351 more words)Show less

Bootstrap When Missing

  1. Detect current state:
    • rg --files -g 'package.json' -g 'biome.json*'
    • rg -n '"@biomejs/biome"|"eslint"|"prettier"|"stylelint"' --glob 'package.json' .
  2. Prefer a repo-local pinned install:
    • npm i -D -E @biomejs/biome
  3. Create config deliberately:
    • npx @biomejs/biome init
  4. Add repeatable commands to AGENTS.md and package.json, then verify with:
    • npx @biomejs/biome check .
    • npx @biomejs/biome check . --write
  5. Return status: configured if Biome is now wired with explicit ownership, or status: improved if the existing setup was tightened.
  6. Return status: not_applicable when the repo intentionally stays on ESLint-centered ownership and no migration or comparison was requested.

Handle Failures

  • Missing-rule parity with specialized ESLint plugins is an ownership problem; keep ESLint for those files until the gap is intentionally closed.
  • Overly broad --write runs can cause large churn; start with bounded folders or changed files first.
  • Generated assets or vendored code should be excluded in biome.json before trusting the signal.
  • If developers complain that Biome and ESLint disagree, define file ownership instead of running both broadly on the same surface by accident.

Deliver

  • explicit Biome ownership and version pinning
  • checked-in config and repeatable check commands
  • a migration or coexistence plan versus ESLint and other frontend tools

Validate

  • the chosen ownership model is documented
  • CI and local runs use the same Biome version
  • the target globs exclude generated and vendored assets
  • downstream build or test flows still pass after --write runs

Ralph Loop

  1. Plan: analyze current state, target outcome, constraints, and risks.
  2. Execute one step and produce a concrete delta.
  3. Review the result and capture findings.
  4. Apply fixes in small batches and rerun checks.
  5. Update the plan after each iteration.
  6. Repeat until outcomes are acceptable.
  7. If a dependency is missing, bootstrap it or return status: not_applicable with a reason.
Required Result Format
  • status: complete | clean | improved | configured | not_applicable | blocked
  • plan: concise plan and current step
  • actions_taken: concrete changes made
  • verification: commands, checks, or review evidence
  • remaining: unresolved items or none

Example Requests

  • "Replace Prettier and basic linting with Biome in this repo."
  • "Add Biome to the frontend under ClientApp."
  • "Explain whether we should keep ESLint after adding Biome."

© managedcode, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file in catalog/Tools/Biome/skills/biome of managedcode/dotnet-skills.

  • SKILL.md
  • manifest.json

Open the folder on GitHubat commit 535dd55

Compare with similar skills

Biome next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Biome compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Biome this skillmanagedcode/dotnet-skills486—~1.7kAutomated safety check: PassMIT
Ultraciteagustinusnathaniel/nextarter-tailwind1252 repos~1.2kAutomated safety check: PassMIT
Code Qualityredis/RedisInsight8.9k—~1.2kAutomated safety check: PassCustom licence
Port Ruleweb-infra-dev/rslint460—~1.7kAutomated safety check: PassMIT
Migrate OxlintAsvarox/allkaraoke2614 repos~2.5kAutomated safety check: PassNone
Git HooksProrise-cool/Claude-Code-Multi-Agent305—~3.6kAutomated safety check: NotesNone

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  • Code Quality

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Works with

Categories

Questions about Biome

What does Biome do?

Use Biome in .NET repositories that ship Node-based frontend assets and want a fast combined formatter-linter-import organizer for JavaScript, TypeScript, CSS, JSON, GraphQL, or HTML. Biome is an agent skill from managedcode/dotnet-skills.NET repositories that ship Node-based frontend assets and want a fast combined formatter-linter-import organizer for JavaScript, TypeScript, CSS, JSON, GraphQL, or HTML.

When should I use Biome?

Biome fits situations like: @biomejs/biome setup; fast frontend formatting and linting; replacing overlapping frontend style tools deliberately; : ESLint-only plugin coverage.

How do I install Biome in Claude Code?

Run `npx skills add managedcode/dotnet-skills --skill biome -a claude-code`. Or copy the skill folder (catalog/Tools/Biome/skills/biome in managedcode/dotnet-skills) into .claude/skills/biome in your project. Claude Code loads it when a task matches its description.

How do I install Biome in Codex?

Run `npx skills add managedcode/dotnet-skills --skill biome -a codex`. Or copy the skill folder (catalog/Tools/Biome/skills/biome in managedcode/dotnet-skills) into .agents/skills/biome in your project. Codex loads it when a task matches its description.

Can I use Biome in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add managedcode/dotnet-skills --skill biome -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/biome, .gemini/skills/biome, .github/skills/biome and .opencode/skills/biome in your project.

What does Biome need to run?

Going by SKILL.md and its folder, Biome needs the command-line tools its instructions call (npx, rg and npm). Our summary lists: Node.js. Compatibility (from SKILL.md): Requires a .NET repository with frontend assets managed through Node or a standalone Biome binary workflow; keep ownership explicit versus ESLint, Stylelint, and webhint..

Does Biome access the network?

SKILL.md names 1 domain. As links in the text: github.com. This is read from the text; nothing was executed.

Is Biome safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Biome use?

Biome is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Biome use?

About 1.7k tokens (SKILL.md is roughly 7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Biome?

Skills that share tags, products or a category with Biome: Ultracite (agustinusnathaniel/nextarter-tailwind, 125 stars), Code Quality (redis/RedisInsight, 8.9k stars), Port Rule (web-infra-dev/rslint, 460 stars) and Migrate Oxlint (Asvarox/allkaraoke, 261 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Biome?

managedcode (a GitHub organization) maintains it in managedcode/dotnet-skills, which has 486 GitHub stars. The repository holds 81 skills in this directory. The repository was last updated on October 7, 2026.

Source: managedcode/dotnet-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.