biomejs/biome's Claude Code Plugin for Biome Contributors

What is the biomejs/biome plugin, actually

biomejs/biome is the source repository for Biome, the Rust based formatter and linter for JavaScript, TypeScript, JSX, JSON, CSS, and GraphQL (25,539 GitHub stars). Inside that same repository sits a small Claude Code plugin: 11 skills that Biome's own contributors use while working on the toolchain itself. Every one of them is scoped, in its own description, to coding agents working on the Biome codebase.

This is not a plugin that formats or lints your project's code. It is procedural knowledge for people changing Biome's own parser, formatter, analyzer, or documentation, so if you are not editing Biome's source tree, there is nothing here for you to invoke. Formatting or linting your own JavaScript, TypeScript, or CSS with Biome is a separate thing entirely, done with the Biome CLI, and does not need this listing at all.

What is inside

The 11 skills split into four jobs.

Compiler internals: parser-development covers writing parsers with error recovery for a new language, including grammar definitions in Biome's own .ungram format, for JavaScript, CSS, JSON, HTML, and GraphQL. formatter-development covers Biome's IR based formatter, comment handling, snapshot tests, idempotency failures, and comparing output against Prettier. lint-rule-development scaffolds a new lint or assist rule, including code actions and configurable options. type-inference covers Biome's Salsa backed type system for JavaScript and TypeScript, for type aware rules and the analyzer's tracked queries. diagnostics-development covers writing the error messages, warnings, and advice a user sees when a rule fires.

Testing and documentation: testing-codegen covers snapshot testing and the code generation commands a change to the parser, analyzer, or formatter needs afterward. doc-comments sets the house style for inline comments read by future Biome contributors, separate from the end user facing text generated from a lint rule's own doc block.

Release and migration: changeset explains when and how to write a changeset entry so a user facing change reaches the changelog correctly. eslint-migrate-options is narrower than lint-rule-development: it applies once a Biome rule already exists and has an ESLint equivalent with configurable options, so the migration path can carry those options across instead of only mapping severity.

Process: biome-code-review is a static, read only review of a pull request, branch, commit range, or diff against Biome's own conventions, covering lint rule placement, diagnostics quality, parser error recovery, formatter idempotency, codegen freshness, and changesets. It reports findings only, it does not edit files or run the project's build, tests, or codegen. syntax-text-handling covers the syntax node APIs, string extraction and embedded language handling that come up in more than one part of the codebase.

When it pays off, and when it doesn't

This plugin only does something if you have Biome's own source checked out and are changing it: adding a lint rule, fixing the parser, or opening a pull request against the project. If you just want your own JavaScript, TypeScript, or CSS formatted and linted, installing it gives you nothing. None of its 11 components touch your project's code, they touch Biome's own Rust and JavaScript internals. Flowy indexes it as the contributor tooling it is, not as something a typical Biome user would reach for.

How do I install it

Flowy indexes biomejs/biome from its public GitHub repository. The skills live in the repository's own skills directory alongside its AGENTS.md conventions file, so anyone can read them straight from the source before deciding whether they apply. Install from the listing page linked at the top of this guide, and the 11 skills above become available in that session.