Biome

Fast, unified linting, formatting, and import organization for JavaScript, TypeScript, JSX, CSS, and GraphQL. Biome 2.4 provides type-aware linting without the TypeScript compiler, GritQL plugins for custom rules, and domain-based rule grouping. Single binary, zero config by default, 97% Prettier compatibility.

Critical Rules

Always use biome check, not separate lint + format

biome check runs formatter, linter, and import organizer in one pass. Never call biome lint and biome format separately in CI - use biome check (or biome ci for CI mode).

biome.json lives at project root

Every project needs one biome.json at the root. Monorepo packages use nested configs with "extends": "//" to inherit from root. Never use relative paths like "extends": ["../../biome.json"].

Use --write to apply fixes, not --fix