ESLint + Prettier Migration

Use this skill to migrate existing lint/format toolchains to BiomeJS with predictable risk.
Run ESLint migration first, then Prettier migration.

Workflow

1. Confirm migration scope:

• ESLint only
• Prettier only
• Both ESLint and Prettier

2. Follow the migration playbook:

• references/eslint-prettier-migration.md

3. Run migration with explicit flag choices:

• biome migrate eslint --write
• Optionally add --include-inspired if user wants broader parity with inspired rules.
• Optionally add --include-nursery only when user accepts unstable rules.
• biome migrate prettier --write after ESLint migration.

4. Review migration output before mass rewrites:

• Verify generated biome.json for renamed rules, overrides, globals, and ignore behavior.
• Confirm ESLint migration may overwrite prior Biome baseline (for example, linter.rules.recommended can change).

5. Validate and stabilize:

• Run biome check .
• Then run biome check --write . after confirming file scope
• If migration introduces too many new lint failures, use:
  biome lint --write --unsafe --suppress="suppressed due to migration"

6. Finalize CI checks:

• Run biome ci .

Operational Defaults

Use these defaults unless user asks otherwise:

• Ensure biome.json exists before migration (biome init if needed)
• Use official migration commands before manual config editing
• Review generated rule mapping and overrides manually
• Align ignore behavior via VCS integration when needed (vcs.enabled, vcs.clientKind, vcs.useIgnoreFile)
• Use EN docs as canonical references when migration behavior is ambiguous

References

• ESLint/Prettier migration playbook: references/eslint-prettier-migration.md