dotnet-biome

A guide for using Biome, one command-line tool that formats and checks frontend files such as JavaScript, TypeScript, CSS, JSON, GraphQL, and HTML.

In plain words
What is it for?
Choosing and configuring Biome in a .NET project, deciding whether it replaces or works alongside ESLint, and adding repeatable local or CI checks.
Why use it?
It can simplify projects that would otherwise use separate formatting, linting, and import-order tools, while making ownership of those checks clear.

Skill for Claude CodeCodex

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/managedcode/prompterone/dotnet-biome
Any agent
npx skills add managedcode/PrompterOne --skill dotnet-biome
Clone the repo
git clone --depth 1 https://github.com/managedcode/PrompterOne

Made for: Claude Code, Codex.

Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,161 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00068 $0.01161
Opus 5 $0.00034 $0.00580
Sonnet 5 $0.00014 $0.00232
Haiku 4.5 $0.00007 $0.00116

Measured 2d ago against content hash 8e516a4637a6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dotnet-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 2d 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:

.codex/skills/dotnet-biome/SKILL.md · 104 lines

How it starts

The opening of the file, as written. The whole thing — 104 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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 dotnet-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.

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.

Read the full file on GitHub · 104 lines

Files

What ships with it

1 file 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. 2d ago First seen · 104 lines · 68 tokens per session scan A 8e516a4637a6

Subscribe to this mod's changes

dotnet-biome is a skill published in the GitHub repository managedcode/PrompterOne (42 stars, last pushed 3mo ago), licensed MIT. It adds 68 tokens to every session and 1,161 once invoked, about $0.0003 per session on Opus 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 2026-08-30.

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