Why does my vision fine-tuning job keep failing?

It is not a mere request ID, it is the whole API on both endpoints that is misconfigured and broken using image input with ft:gpt-4.1 for anyone, that has been ongoing for nearly a week.

Fine-tuned Model Vision Capabilities Lost Bugs

A fine-tuned model (ft:gpt-4.1-2025-04-14:cvm:v1-optimized2:CtvBgA1l) that previously accepted vision inputs (image_url) now rejects them with error 400. Error code: 400 - { ‘error’: { ‘message’: ‘Invalid content type. image_url is only supported by certain models.’, ‘type’: ‘invalid_request_error’, ‘param’: ‘messages.[1].content.[0].type’, ‘code’: None } } It was working when I had image inputs last week, January 27th 2026. I have run my same source code without any changes utilizing the sa…