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"question" tool schema causes "400 Bad Request" with Gemini/Vertex AI` #11413
Description
Description
I am encountering compatibility issues when using Google Gemini models (via Custom Provider). Even after removing all plugins (like oh-my-opencode), the chat still fails with a 400 error unless the built-in question tool is explicitly disabled.
It appears the JSON Schema definition for the question tool contains keywords or structures that are incompatible with the strict schema requirements of Google's Vertex AI/Gemini API.
Plugins
oh my opencode
OpenCode version
1.1.47
Steps to reproduce
Using the following opencode.json configuration triggers the error:
{
"plugin": [],
"tools": {
"question": true // Default behavior
}
}
### Screenshot and/or share link
<img width="617" height="212" alt="Image" src="https://github.com/user-attachments/assets/932aca33-78d0-4c7e-af7b-2b7bc68debda" />
<img width="827" height="466" alt="Image" src="https://github.com/user-attachments/assets/2898c1b4-9b53-485d-a826-2f005f6f583f" />
### Operating System
Windows 10
### Terminal
Windows TerminalMetadata
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rekram1-node commentedon Jan 31, 2026
Can you share your error? I tried using google and it works fine
guhur1 commentedon Jan 31, 2026
guhur1 commentedon Jan 31, 2026
fix: address tool/plugin issues anomalyco#11413, anomalyco#11130, ano…
test: add unit tests for anomalyco#11413, anomalyco#11130, anomalyco#…
rekram1-node commentedon Mar 25, 2026
I cannot replicate the issue
github-actions commentedon Jul 3, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.