Is Fine-tuning gpt-4o-mini compatible with Structure-outputs?

Hi everyone!

I am working on a project where given a text as input, i need to extract several fields in JSON format.

This is a fake example to understand my issue
“I want to find a cheap and reliable car for 2000” → {“object”: “car”, “price”: 2000", “status”: “reliable”}

I have been able to train both gpt3.5 turbo and gpt-4o-mini, and both are working great.

However, sometimes the models hallucinate, adding new fields that they haven’t seen before. I need to find some way to limit the generated fields.

For that reason, i ended up in this post, where Structure-Output where released.
https://platform.openai.com/docs/guides/structured-outputs

However, after using my Structure JSON Output with my gpt-4o-mini-finetune model, i see some new fields generated that are not in the JSON template.

I also tried that Structure-output with the base gpt-4o-mini model (without fine-tuning), and in this case it worked.

So my question is, are structure-output actually working with custom fine-tuned models?

Thanks in advance :slight_smile:

2 Likes

I have seen the same pattern here, seeing refusal=None, while the output doesn’t follow the expected json format