Litestar validates that handlers with 204 status codes cannot return a response body. The delete_attachment handler was declared as -> Response and returned Response(content=None, status_code=204), which caused ImproperlyConfiguredException at startup and crashed all workers. Change return type to None and move status_code to the @delete decorator. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>