Google AI Studio Build Agent returns “Invalid argument” immediately — Gemini 3.8 Flash, Ran for 0s

Google AI Studio
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1

Hello Google AI Studio team,

I am experiencing a persistent issue in Google AI Studio Build mode.

The Build Agent immediately returns:

“Invalid argument.”

The UI shows:

Gemini 3.8 Flash
Ran for 0s

The issue originally occurred after a frontend implementation task in an existing app project.

After that, every request started failing immediately.

I tested with a completely simple prompt:

“Reply exactly: OK
Do not inspect or modify the app.”

The result was still:

Gemini 3.8 Flash
Ran for 0s
Invalid argument.

I also opened a new Gemini conversation inside the same project, but the same error occurred.

Therefore, the issue does not appear to be caused by the prompt content or by the specific coding task.

Expected behavior:
The Build Agent should process the prompt normally and return “OK”.

Actual behavior:
The request is rejected immediately with “Invalid argument” before the model starts processing.

Environment:

  • Google AI Studio Build
  • Model: Gemini 3.8 Flash
  • Browser: Google Chrome
  • OS: macOS
  • Execution time shown: Ran for 0s
  • New conversation also fails
  • Simple text-only prompt also fails

Approximate time issue started:
2 October 2026, around 13:00–14:00 ICT (UTC+7)

App ID:
[INSERT APP ID HERE]

Important:
I have not restored an older project version yet because the previous Build Agent run may have successfully written some code before the final tool error occurred.

Could you please check whether the project’s Build Agent session/tool state or model invocation payload has become invalid?

Screenshots are attached.

Thank you.

image
image1028×808 35.9 KB

2

Hi,

I get the exact same behavior since yesterday in the afternoon.

I noticed that I add a file db.json in red in my project files, impossible to edit, download, delete…

So I restored my project before the last prompt and it works back correctly…

Regards

3

I followed your method and managed to resolve the issue. Thank you very much for sharing this content.

4

Hello @Ti_n_Nguy_n_Van1 , @Alain_BONNEFOY1 ,

can you share below details via DM?

  • Confirm whether this behavior appears across other applications or remains isolated to this single app.

  • The exact prompt in use when the error appeared.

  • Current account tier, whether free tier or a paid plan.

  • The applet ID to assist with reviewing this specific case.