Hello, Since today (December 23, 2025, KST), I have noticed an issue where Gemini starts responding in a structured / JSON-like format only when Function Calling is enabled. Until yesterday, even with Function Calling added/enabled, Gemini responded in normal natural language unless it was expli…

Same thing, started a few hours ago it seems, at least with gemini-3-flash-preview

Checking server logs, it appears to have started around 2025-12-22 23:00:00 UTC, and the issue remains unresolved. We haven’t received a complete response, so we’d appreciate it if you could take action quickly.

We are facing the same issue. This bug only occurs with Gemini 3 models such as gemini-3-pro-preview (Confirmed) and gemini-3-flash-preview (I’m not sure, but it’s very likely). This bug does not happen with gemini-2.5-pro. Additionally, gemini-3-pro-preview tends to calls tools in the wrong way…

I am using the gemini java sdk, same thing 3.0 flash preview started today, it was working great thought, with good tool calling discrimination with the current issue, text parts sometimes show like this { “text”: “Hello! I’m Anahata, your AI butler here in NetBeans. I’m ready to help you with yo…

I’m using js-genai sdk, and it doesn’t seem to be a problem specific to the sdk.

[image] Structured output ignoring schema field names Gemini API Thank you for the update. It is great to hear that the Structured Output feature is working as expected. From this it looks like there was an update in gemini 3 for structured output.

Yes! Because it responds as if a structured output were defined. The weirdest thing we tried https://aistudio.google.com/ with a defined tool and it answer as usual :neutral_face:

Hi @user4064 , welcome to the community! Could you help me out with a few more details so that we can analyze this better? Are you using any SDKs? If yes, which one? Have you tried providing system instructions specifically for the same? If using any other SDKs other than the Google GenAI SDK, have…

[image] Srikanta_K_N: thought_signature I’m using the js-genai SDK 1.34.0 and constructing a history using the GoogleGenAI Chats object. I’m also correctly inserting thought_signature. Until yesterday, it was processing thousands of requests without issue, but today, the responses suddenly b…

Three different java projects, all using the genai java sdk (and just updated to the latest 1.32) All working like a charm yesterday, only seen in gemini 3 flash preview [image] GitHub - anahata-os/anahata-netbeans-ai: A NetBeans plugin that brings the power of Google... A NetBe…

Gemini responds with structured / JSON-like output only when Function Calling is enabled

Gemini API

user4064 December 23, 2025, 5:45am 10

From this it looks like there was an update in gemini 3 for structured output.

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Gemini responds with structured / JSON-like output only when Function Calling is enabled

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