Error message in UI

[openlabforkd]

What happened?

I am using librechat with custom open api endpoint.
I want to pass error message to user if the question has invalid or malformed content.

I am passing the response as following from my fast api middleware.

error_response = {
                        "error": {
                            "message": "Invalid user question: your request could not be processed because it does not conform to the expected format or content requirements.",
                            "type": "invalid_request_error",
                            "param": "user_question",
                            "code": "invalid_request",
                            "sequence_number": 1,
                            
                        }
                    }
                    return JSONResponse(status_code=400, content=error_response)

However, error is not displayed correctly on UI.
I just see following message on ui.

Version Information

I am using librechat release published in June 2025

Steps to Reproduce

Create custom open ai api endpoint using fast api

Use it for libreChat ui

try to send error message before sending user message to llm for further processing.

What browsers are you seeing the problem on?

Chrome

Relevant log output

here is part of response body for error.

"unfinished":false,"error":true,"final":true,"text":"{\"type\":\"invalid_request_error\"}","isCreatedByUser":false,"spec"

Screenshots

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