Gemini-flash-2-5 for bounding box detection performs worse when using thinking

Gemini API
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1

For our bounding box detection tasks on documents, we found that gemini-flash-2.5 performs quite well, but only if thinking_budget=0.

If thinking_budget>0 the bounding boxes are much worse and sometimes quite far away from the actual object one is trying to detect.

Has anybody made similar observations?

3

Hi @TheVoogler , Welcome to the forum.

Thanks for pointing out the issue. I have noticed the same thing, when thinking_budget is greater than 0, the model’s performance seems to drop.

I will be escalating this to the team.