## Implementation Complete ### Changes Made 1. **routes.py** - Added create_error_response() helper function that creates JSONResponse with OpenAI-compatible error format 2. **main.py** - Added RequestValidationError exception handler to convert Pydantic validation errors to OpenAI format 3. **test_error_handling.py** - Created comprehensive test suite (20 tests) verifying all error responses match OpenAI schema 4. Updated existing tests to check new error format ### Test Results All 336 tests pass including 20 new error handling compliance tests. ### Error Format All errors now return: {"error": {"message": str, "type": str, "param": str|null, "code": str|null}}