This is an issue discovered during testing using the recently available gpt-5.1-chat-latest model.
The documentation indicates that gpt-5.1-chat-latest does not support reasoning.
However, during testing, I confirmed that the reasoning token was used.
Used code
const openai = new OpenAI({ apiKey: process.env.AIAI_OPENAI_API_KEY });
(async () => {
const result = await openai.responses.create({
model: 'gpt-5.1-chat-latest',
input: 'How much gold would it take to coat the Statue of Liberty in a 1mm layer?',
reasoning: { effort: null },
});
console.log(result);
})();
Result
{
usage: {
input_tokens: 25,
input_tokens_details: { cached_tokens: 0 },
output_tokens: 179,
output_tokens_details: { reasoning_tokens: 128 },
total_tokens: 204
}
}
I thought that when using the gpt-5.1-chat-latest model, reasoning_tokens should not be used. If I misunderstood something, please let me know.
Thank you.
)
