FastAPI 0.141

Apply the Pydantic 2.13 and Python 3 prompts first. These rules cover FastAPI 0.141 dependency injection, authentication, request processing, response filtering, cookies, sessions, HTML output, asynchronous work, proxy configuration, and deployment.

Models and dependencies

• Use distinct Pydantic models for input, internal state, persistence, and public output.
• Expect FastAPI 0.141 to validate parsed JSON bodies and query, path, header, and cookie values with Pydantic's Python-mode validate_python(), not JSON mode. Strict mode there, model-wide or per field, rejects ISO date and datetime strings, UUID strings, enum values, and all Decimal input in bodies, and rejects every non-string scalar type, such as int or bool, in parameters.
• Put Field(strict=True) on the str, int, float, and bool body fields where coercion matters. Keep UUID, Decimal, date, and enum fields lax with explicit constraints, using Field(strict=False) inside an otherwise strict model, instead of dropping strictness from the whole model. When a body needs JSON-mode strictness, validate it with Model.model_validate_json(await request.body()) instead of declaring a body parameter, and check Content-Type yourself because FastAPI's check no longer applies.
• Put authentication and authorization dependencies on every protected router or operation, including custom API routes; protect mounted applications and generated documentation separately because they do not inherit app/router dependencies.
• Route any Starlette HTTPEndpoint subclass with an explicit methods= list