Biome is a web-development toolchain that formats and checks source code for languages such as JavaScript, TypeScript, JSX, and CSS. Developers use its command-line and language-server interfaces to maintain code quality in web projects. Catalogue add-ons extend workflows around the toolchain.
Borrowing it
Nothing to install: this file belongs to biomejs/biome. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/biomejs/biome/main/.agents/skills/changeset/SKILL.mdgit clone --depth 1 https://github.com/biomejs/biomeWrote 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.
[](https://agentmods.dev/skills/biomejs/biome/changeset)<a href="https://agentmods.dev/skills/biomejs/biome/changeset"><img src="https://agentmods.dev/badge/skills/biomejs/biome/changeset/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.
<a href="https://agentmods.dev/skills/biomejs/biome/changeset"><img src="https://agentmods.dev/badge/skills/biomejs/biome/changeset.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Snyk pass
- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00054 | $0.00734 |
| Opus 5.5 | $0.00022 | $0.00294 |
| Sonnet 5.5 | $0.00011 | $0.00147 |
| Haiku 4.5 | $0.00005 | $0.00073 |
Grade A, and why
changeset 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 22d 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.
How it starts
The opening of the file, as written. The whole thing — 83 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Changesets
Changesets describe user-visible behavior for release notes. Root AGENTS.md defines when automated contributions require one; CONTRIBUTING.md is canonical for package selection, versioning, branch targets, and prose format.
Decide Whether One Is Required
A changeset is required for behavior visible to users of the CLI, libraries, published crates, diagnostics, parser, formatter, linter, or assists.
No changeset is needed for an internal refactor with identical behavior, tests only, CI/build maintenance, or documentation-only edits.
Before opening a PR, explicitly confirm the user-facing classification as required by AGENTS.md. Do not infer user visibility only from the files changed.
Choose the Release Level
| Change | Level | Target |
|---|---|---|
| Bug fix or non-breaking behavior correction | patch |
main |
| New nursery lint rule | patch |
main |
| New user-facing feature or nursery promotion | minor |
next |
| Breaking user API change | major |
next |
Nursery rules are the exception to the usual new-feature mapping because they do not follow semantic versioning. Verify unusual cases against the current versioning policy.
Create the File
Run just new-changeset-empty to generate an empty file.
just new-changeset-empty
An empty generated entry starts with frontmatter delimiters. Replace that frontmatter with the package and release level rather than appending a second block:
---
"@biomejs/biome": patch
---
Description.
Use #### or ##### for headings inside a longer entry. Other heading levels interfere with changelog generation.
Write the Entry
- Describe user-visible behavior, not implementation.
- Use one to three sentences unless the impact genuinely needs an example.
- Use past tense for the contribution and present tense for resulting Biome behavior.
- Start bug fixes with the linked issue when one exists. If a link doesn't exist, start with a verb.
- Link rule and assist names to their Biome website pages.
- End every sentence with a full stop.
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.
- 22d ago Changed 9f8f1cd2fb7d
- 1mo ago First seen · 83 lines · 54 tokens per session scan A 1aaf64cff074
changeset is a skill published in the GitHub repository biomejs/biome (26,016 stars, last pushed today), licensed Apache-2.0. It adds 54 tokens to every session and 734 once invoked, about $0.0002 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 2026-08-30.
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