Use when creating or modifying backend code: API routes, use cases, domain models, repositories, infrastructure services, or dependency injection configuration. Follows Hexagonal Architecture, DDD, and DIOD conventions.
Use when creating or modifying database schemas, migrations, or SQL scripts. Follows PostgreSQL conventions: NOT NULL for required fields, plural table naming, and TEXT with CHECK constraints over VARCHAR/CHAR.
Use when creating or modifying tests: unit tests, Object Mothers for test data, or hand-written Mock Objects for domain interfaces. Follows the project's testing conventions with jest, should pattern mocks, and faker-based mothers.