Biome Configuration Deep Dive for Nx

Use this guide when you need advanced configuration details beyond the SKILL hub.

Root Configuration Baseline

Create and maintain one root biome.json as the default authority:

{
  "$schema": "https://biomejs.dev/schemas/1.9.4/schema.json",
  "files": {
    "ignoreUnknown": false
  },
  "formatter": {
    "enabled": true,
    "indentStyle": "space",
    "indentWidth": 2
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true
    }
  }
}

Nx Target Defaults for Cache Stability

Ensure lint and format targets include config and dependency inputs:

{
  "targetDefaults": {
    "biome-lint": {
      "cache": true,
      "inputs": [
        "default",
        "^default",
        "{workspaceRoot}/biome.json",
        { "externalDependencies": ["@biomejs/biome"] }
      ]
    },
    "biome-format": {
      "cache": true,
      "inputs": [
        "default",
        "^default",
        "{workspaceRoot}/biome.json",
        { "externalDependencies": ["@biomejs/biome"] }
      ]
    }
  }
}

Advanced Rule Tuning Strategy

• Keep recommended: true as baseline.
• Override only rules that show recurring false positives for your repository.
• Prefer narrow path-scoped exceptions over global relaxations.
• Record reason + expiration for temporary suppressions.

Example scoped override (temporary migration guardrail):

{
  "overrides": [
    {
      "includes": ["apps/legacy/**"],
      "linter": {
        "rules": {
          "style": {
            "noNonNullAssertion": "off"
          }
        }
      }
    }
  ]
}

Performance Optimization Tips

• Run nx run-many -t biome-lint instead of ad hoc per-project loops.
• Use Nx affected workflows in CI to limit scope.
• Reset daemon cache (nx reset) after plugin or target definition changes.
• Keep plugin inference logic lightweight; avoid expensive filesystem traversal.

Verification Checklist

• biome.json exists at workspace root.
• biome-lint and biome-format are cache-enabled.
• Cache inputs include root config and external Biome dependency.
• CI verification runs non-mutating checks.