Agent-skills biome-js

This skill should be used when the user asks to "configure Biome", "extend biome config", "set up BiomeJS", "add biome overrides", "biome lint-staged", "fix biome errors", or mentions biome.jsonc, Biome linting, or Biome formatting configuration.

install

source · Clone the upstream repo

git clone https://github.com/PaulRBerg/agent-skills

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/PaulRBerg/agent-skills "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/biome-js" ~/.claude/skills/paulrberg-agent-skills-biome-js && rm -rf "$T"

manifest: skills/biome-js/SKILL.md

source content

BiomeJS Skill

Quick guidance for BiomeJS configuration based on Sablier project patterns.

Core Concepts

Extending Shared Configs

Extend shared configs via npm package exports. The consuming project must always provide its own

files.includes

{
  "$schema": "./node_modules/@biomejs/biome/configuration_schema.json",
  "extends": ["@sablier/devkit/biome"],
  "files": {
    "includes": ["**/*.{js,json,jsonc,ts}", "!node_modules/**/*"]
  }
}

For UI projects, extend both base and ui configs:

{
  "extends": ["@sablier/devkit/biome/base", "@sablier/devkit/biome/ui"],
  "files": {
    "includes": ["**/*.{css,js,jsx,json,jsonc,ts,tsx}"]
  }
}

Monorepo Inheritance

In monorepos, workspace configs inherit from root using

"//"

// packages/my-package/biome.jsonc
{
  "extends": ["//"],
  "overrides": [
    // package-specific overrides
  ]
}

File Includes Pattern

Always specify

files.includes

explicitly. Common patterns:

Project Type	Pattern
Library	`*/.{js,json,jsonc,ts}`
UI/Frontend	`*/.{css,js,jsx,json,jsonc,ts,tsx}`
With GraphQL	`*/.{css,graphql,js,jsx,json,jsonc,ts,tsx}`

Exclusions:

!node_modules/**/*

!**/generated

!dist

Common Overrides

Test Files

Relax strict rules in test files:

{
  "overrides": [
    {
      "includes": ["**/tests/**/*.ts", "**/*.test.ts"],
      "linter": {
        "rules": {
          "style": {
            "noNonNullAssertion": "off"
          },
          "suspicious": {
            "noExplicitAny": "off"
          }
        }
      }
    }
  ]
}

Generated/ABI Files

Disable sorting and compact formatting for generated code:

{
  "overrides": [
    {
      "includes": ["**/abi/**/*.ts", "**/generated/**/*.ts"],
      "assist": {
        "actions": {
          "source": {
            "useSortedKeys": "off"
          }
        }
      },
      "javascript": {
        "formatter": {
          "expand": "never"
        }
      }
    }
  ]
}

Import Restrictions

Enforce barrel imports for specific modules:

{
  "overrides": [
    {
      "includes": ["src/**/*.{ts,tsx}"],
      "linter": {
        "rules": {
          "correctness": {
            "noRestrictedImports": {
              "level": "error",
              "options": {
                "paths": {
                  "@/core": "Import from @/core (barrel) instead of subpaths"
                }
              }
            }
          }
        }
      }
    }
  ]
}

Key Rules Reference

Rule	Default	Rationale
`noFloatingPromises`	error	Floating promises cause bugs
`noUnusedImports`	off	Allow during dev, enforce in pre-commit
`noUnusedVariables`	error	Keep code clean
`useImportType`	warn (separatedType)	Explicit type imports
`useSortedKeys`	on	Consistent object ordering
`useSortedClasses`	warn (UI)	Tailwind class sorting
`useFilenamingConvention`	kebab/camel/Pascal	Flexible naming
`noVoid`	off	Useful for useEffect callbacks
`useTemplate`	off	Allow string concatenation

Git Hooks Integration

Lint-Staged Configuration

Standard pattern for pre-commit hooks:

// .lintstagedrc.js
module.exports = {
  "*.{json,jsonc,ts,tsx}": "bun biome check --write",
  "*.{md,yml,yaml}": "bun prettier --cache --write",
  "*.{ts,tsx}": "bun biome check --write --only=correctness/noUnusedImports",
};

The separate

noUnusedImports

pass enforces import cleanup only at commit time, not during development.

UI-Specific Configuration

For frontend projects with Tailwind CSS:

{
  "css": {
    "parser": {
      "tailwindDirectives": true
    }
  },
  "assist": {
    "actions": {
      "source": {
        "useSortedAttributes": "on"
      }
    }
  },
  "linter": {
    "rules": {
      "nursery": {
        "useSortedClasses": {
          "fix": "safe",
          "level": "warn",
          "options": {
            "attributes": ["classList"],
            "functions": ["clsx", "cva", "cn", "tv", "tw"]
          }
        }
      }
    }
  }
}

Biome

v2.4.0+

auto-enables CSS Modules parsing for

*.module.css

, so explicit

"cssModules": true

is usually unnecessary unless your project needs non-standard behavior.

Biome v2.4+ Notes

```
biome check
```
and
```
biome ci
```
now support
```
--only
```
and
```
--skip
```
for targeted rule/action runs.
```
biome check --write
```
now also applies formatting when applying fixes.
Config lookup now also supports hidden files:
```
.biome.json
```
and
```
.biome.jsonc
```
.
Config lookup now also supports user config directories (for example,
```
$HOME/.config/biome
```
on Linux/macOS equivalents).
New formatter option
```
formatter.trailingNewline
```
can disable trailing newline insertion.
HTML formatter behavior changed significantly in
```
v2.4.0
```
; expect larger diffs in HTML/Vue/Svelte/Astro if formatter support is enabled.

Troubleshooting

Common Issues

"No files matched": Check

files.includes

patterns match your file structure.

Conflicting rules: Overrides are applied in order; later overrides take precedence.

Schema errors: Use local schema reference for IDE support:

"$schema": "./node_modules/@biomejs/biome/configuration_schema.json"

Biome vs Prettier

Biome handles JS/TS/JSON/CSS formatting. Use Prettier for:

Markdown (
```
.md
```
,
```
.mdx
```
)
YAML (
```
.yml
```
,
```
.yaml
```
)

Additional Resources

Examples

Working examples in

./examples/

./examples/base-config.jsonc
- Minimal library configuration
./examples/ui-config.jsonc
- Frontend project with Tailwind
./examples/lint-staged.js
- Pre-commit hook configuration

Full Documentation

For advanced features, migrations, or complete rule reference, consult the official Biome documentation via Context7 MCP:

Use context7 to fetch Biome documentation for [specific topic]

The official docs at biomejs.dev should be consulted as a last resort for features not covered here.