biome

Use this skill when working on Biome's Salsa-backed JavaScript and TypeScript inference, including type-aware lint rules, raw collection or inferred representations, analyzer requests, tracked queries, import or cycle resolution, profiling, and Salsa invalidation tests. Do not use for standalone CSS/HTML module-graph data unrelated to JS/TS inference or for ordinary semantic binding analysis.

Use this skill when selecting or running Biome test fixtures, quick tests, `insta` snapshot workflows, expectation comments, orphan checks, or required code generators. Do not use for subsystem implementation design.

Use this skill when implementing or modifying Biome parser behavior, including `.ungram` grammars, lexers, token sources, parse rules, separated lists, error recovery, and parser fixtures. Do not use merely for consuming an existing AST/CST.

Use this skill when creating or modifying Biome lint rules or assists, including analyzer queries, semantic bindings, rule state, code actions, fix safety, options, registration, and end-user rule rustdoc. Also load diagnostics-development for substantial message/advice design and testing-codegen for fixture or snapshot mechanics.

Use this skill when implementing or debugging Biome formatter behavior, IR composition, node rules, layout selection, source-comment handling, verbatim formatting, idempotency, internal specs, or Prettier comparison. Do not use for generic snapshot commands or parser changes.

Use this skill when `biome migrate eslint` must preserve configurable ESLint rule options through source-option models, Biome conversions, typed rule variants, and migration fixtures. Do not use for generated severity-only mapping or general rule-option design.

Use this skill whenever writing or editing Rust `//`, `///`, or `//!` comments in Biome, including comments added incidentally and end-user rustdoc inside lint/assist declarations. For lint/assist rustdoc, also load lint-rule-development for content requirements. Do not use for formatter handling of comments in user code.

Use this skill when designing or implementing Biome user-facing diagnostic presentation or APIs, including messages, advice, markup, details, code frames, categories, severity, and standalone `Diagnostic` types. Do not use for lint matching logic or code-action mutations.

Use this skill when a Biome change may affect users and you must decide whether it needs a changeset, choose the release level, or create and edit `.changeset/*.md` release-note text. Do not use for implementation details or PR descriptions.