Biome Validator

Validates Biome 2.3+ configuration and prevents outdated patterns. Ensures type-aware linting, domains, and modern Biome features are properly configured.

When This Activates

• Setting up linting for a new project
• Before any code quality work
• Auditing existing Biome configurations
• After AI generates biome.json
• CI/CD pipeline validation

Quick Start

python3 ~/.claude/skills/biome-validator/scripts/validate.py --root .
python3 ~/.claude/skills/biome-validator/scripts/validate.py --root . --strict

What Gets Checked

1. Biome Version & Schema

GOOD - Biome 2.3+:

{
  "$schema": "https://biomejs.dev/schemas/2.3.12/schema.json"
}

BAD - Old schema:

{
  "$schema": "https://biomejs.dev/schemas/1.9.0/schema.json"
}

2. Package Version

// GOOD: v2.3+
"@biomejs/biome": "^2.3.0"

// BAD: v1.x or v2.0-2.2
"@biomejs/biome": "^1.9.0"

3. Linter Configuration

GOOD - Biome 2.x:

{
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "suspicious": {
        "noExplicitAny": "warn"
      }
    }
  }
}

4. Biome Assist (2.0+)

GOOD - Using assist:

{
  "assist": {
    "actions": {
      "source": {
        "organizeImports": "on"
      }
    }
  }
}

BAD - Old organizeImports location:

{
  "organizeImports": {
    "enabled": true
  }
}

5. Domains (2.0+)

GOOD - Using domains for framework-specific rules:

{
  "linter": {
    "domains": {
      "react": "on",
      "next": "on"
    }
  }
}

6. Suppression Comments

GOOD - Biome 2.0+ comments:

// biome-ignore lint/suspicious/noExplicitAny: legacy code
// biome-ignore-all lint/style/useConst
// biome-ignore-start lint/complexity
// biome-ignore-end

BAD - Wrong format:

// @ts-ignore  // Not Biome
// eslint-disable  // Wrong tool

Biome 2.3+ Features

Type-Aware Linting

Biome 2.0+ includes type inference without requiring TypeScript compiler:

{
  "linter": {
    "rules": {
      "correctness": {
        "noUndeclaredVariables": "error",
        "useAwaitThenable": "error"
      }
    }
  }
}

Assist Actions

{
  "assist": {
    "actions": {
      "source": {
        "organizeImports": "on",
        "useSortedKeys": "on"
      }
    }
  }
}

Multi-file Analysis

Lint rules can query information from other files for more powerful analysis.

Framework Domains

{
  "linter": {
    "domains": {
      "react": "on",       // React-specific rules
      "next": "on",        // Next.js rules
      "test": "on"         // Testing framework rules
    }
  }
}

Recommended Configuration

{
  "$schema": "https://biomejs.dev/schemas/2.3.12/schema.json",
  "assist": {
    "actions": {
      "source": {
        "organizeImports": "on"
      }
    }
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "complexity": {
        "noForEach": "off"
      },
      "style": {
        "noNonNullAssertion": "off"
      },
      "suspicious": {
        "noArrayIndexKey": "off",
        "noExplicitAny": "warn"
      },
      "correctness": {
        "useAwaitThenable": "error",
        "noLeakedRender": "error"
      }
    },
    "domains": {
      "react": "on",
      "next": "on"
    }
  },
  "formatter": {
    "enabled": true,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineWidth": 100
  },
  "javascript": {
    "formatter": {
      "quoteStyle": "single",
      "trailingCommas": "es5",
      "semicolons": "always"
    }
  },
  "files": {
    "ignore": [
      "node_modules",
      "dist",
      "build",
      ".next",
      "out",
      ".cache",
      ".turbo",
      "coverage"
    ]
  }
}

Deprecated Patterns

Validation Output

=== Biome 2.3+ Validation Report ===

Package Version: @biomejs/biome@2.3.11 ✓

Configuration:
  ✓ Schema version: 2.3.11
  ✓ Linter enabled with recommended rules
  ✓ Using assist.actions for imports
  ✗ No domains configured (consider enabling react, next)
  ✓ Formatter configured

Rules:
  ✓ noExplicitAny: warn
  ✓ useAwaitThenable: error
  ✗ noLeakedRender not enabled (recommended)

Summary: 2 issues found

Migration from ESLint

Step 1: Install Biome

bun remove eslint prettier eslint-config-* eslint-plugin-*
bun add -D @biomejs/biome@latest

Step 2: Create biome.json

bunx biome init

Step 3: Migrate rules

bunx biome migrate eslint --write

Step 4: Update scripts

{
  "scripts": {
    "lint": "biome lint .",
    "lint:fix": "biome lint

...