Gemini 2.5 Flash problems while trying to deactivate thinking

Gemini API
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1

I have a bunch of scripts still using Gemini gemini-1.5-flash-002. I’ve tried to migrate to 2.5 Flash before, but the thinking mode being activated by default results in a much higher cost than I’m able to assume. Problem is, trying to deactivate the thinking mode doesn’t work.

There is already a Github issue:

Even the example in the repo is throwing errors:

google.genai.errors.ClientError: 400 INVALID_ARGUMENT. {‘error’: {‘code’: 400, ‘message’: ‘The model does not support
setting thinking_budget to 0.’, ‘status’: ‘INVALID_ARGUMENT’}}

Does anyone have succesfully deactivated thinking mode?

3

Hi @Belen_Cebrian,

As mentioned in the Gemini thinking  |  Gemini API  |  Google AI for Developers, it is possible to disable “thinking mode” in Gemini 2.5 Flash model by setting the thinking_budget parameter to 0 in the API request. Please see the gist. Here the example output confirms this — thinking_budget=0 is set, the response metadata contains no thoughts_token_count , indicating that no reasoning tokens were generated.

Where as with Gemini 2.5 Pro model, thinking cannot be disabled; attempts to set thinking_budget=0 will result in a 400 INVALID_ARGUMENT error.

Thank you!

5

Thanks, chunduriv! I have tried again and now it works.

1 Like
6

Hi @Belen_Cebrian,

Glad the issue resolved for you.

Thank you!