I’m getting “400 Unsupported parameter: ‘stop’ is not supported with this model.”
This is basic functionality that’s always worked for non-thinking models. Any reason why they removed it with this model?
A decent reason:
The AI could write internally:
“after I’m done I need to write #### at the end…”
Then the reasoning stops with you getting nothing.
GPT-5.1 has the option to set reasoning_effort to 0 so this shouldn’t happen.
I suppose you could write “please” in a request if that is what you want this topic to be.
o1:
user: Write a poem about a bashful penguin. Each line is separated by a line that is only #### (four hash marks).
o4-mini
{'error': {'message': "Unsupported parameter: 'stop' is not supported with this model."
A better reason: OpenAI will do anything they can to push “Responses”.
It does seem like the AI scene gets worse with every new release. Both the API and the models themselves. Google is not much better. Gemini 3.0 preview is also crapy compared to 2.5 pro, honestly.
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