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[Bug] Numeric enum values not stringified for Gemini API #12784
Description
Bug Description
When using Gemini models (gemini-3-pro-preview, gemini-2.5-flash, etc.), OpenCode sends numeric enum values in tool schemas as numbers instead of strings, causing 400 Bad Request errors from the Gemini API.
Error Message
Invalid value at 'tools[0].function_declarations[59].parameters.properties[1].value.enum[0]' (TYPE_STRING), 1
Invalid value at 'tools[0].function_declarations[59].parameters.properties[1].value.enum[1]' (TYPE_STRING), 2
Invalid value at 'tools[0].function_declarations[59].parameters.properties[1].value.enum[2]' (TYPE_STRING), 3
...
Root Cause
Gemini API requires all enum values to be strings. When OpenCode has numeric enum values like [0, 1, 2, 3, 4], they must be converted to ["0", "1", "2", "3", "4"] before sending to Gemini.
Environment
- OpenCode version: Latest (as of Feb 2026)
- OS: macOS
- Model: google/gemini-3-pro-preview, google/gemini-2.5-flash
Reproduction Steps
- Configure OpenCode to use a direct Google AI Studio API key
- Try to use any Gemini model with tool calling
- Observe 400 Bad Request errors with the above message
Expected Behavior
Numeric enum values should be automatically stringified when sending tool schemas to Gemini API.
Notes
- This bug exists in OpenCode core, not in plugins like opencode-antigravity-auth
- Issue was confirmed by disabling all plugins and testing with direct Google API connection
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github-actions commentedon Feb 9, 2026
This issue might be a duplicate of existing issues. Please check:
These issues all involve Gemini API's strict schema validation requirements. Your numeric enum issue may be part of a broader pattern of Gemini schema serialization problems.
Feel free to ignore if your specific case differs from these.
fix(provider): fix property order bug in Gemini numeric enum stringif…
rekram1-node commentedon Feb 9, 2026
are u sure they should be converted to strings? What tool are u using that can handle that? Why not just drop enum and send it as a number field?
github-actions commentedon Apr 11, 2026
To stay organized issues are automatically closed after 90 days of no activity. If the issue is still relevant please open a new one.
fix(llm-proxy): sanitize non-string enums in Gemini tool schemas (arc…