AI "Thought Signatures"

 Thought Signatures  |  Gemini API  |  Google AI for Developers

Thought signatures are encrypted representations of the model's internal thought process and are used to preserve reasoning context across multi-step interactions. When using thinking models (such as the Gemini 3 and 2.5 series), the API may return a thoughtSignature field within the content parts of the response (e.g., text or functionCall parts).