Same...I'm in the same struggle. Did you find a solution?

I have found these two resources and so far i've been unsuccessful but it's there, in the code...anyone else have success with this yet?

https://community.openai.com/t/upload-image-to-assistant-via-api/801717/6

https://geoligard.com/using-laravel-to-interact-with-openai-s-assistants-api-with-vision