Following the discussion in #14964, deprecating ORJSONResponse and UJSONResponse might be premature since exception handlers can't benefit from the new Pydantic serialization introduced in #14962.

Currently, exception handlers must return a Response object, which means they fall back to stdlib json.dumps via JSONResponse, the exact use case where ORJSONResponse was providing free performance gains.

Two possible paths forward:

1. Use Pydantic serialization in JSONResponse

JSONResponse could use TypeAdapter.dump_json internally instead of json.dumps. Though this might impose constraints on the accepted content types.

2. Support typed returns in exception handlers

Allow exception handlers to return dicts or Pydantic models directly, similar to regular route handlers:

class MyErrorBody(BaseModel):
    message: str

@app.exception_handler(MyError, status_code=status.HTTP_422_UNPROCESSABLE_ENTITY)
async def _(request: Request, exception: MyError) -> MyErrorBody:
    return MyErrorBody(message=str(exception))

This would enable Pydantic serialization for exception responses and feed the OpenAPI schema generation with error response types, which is currently not possible.