The environment variable GOOGLE_GENAI_USE_VERTEXAI affects GOOGLE GEMINI

[dielect]

App Version

3.28.1

API Provider

Google Vertex AI

Model Used

gemini-2.5-pro

Roo Code Task Links (Optional)

No response

🔁 Steps to Reproduce

1. macOS 15.6.1 (24G90) Apple M4
2. I previously set Google Gemini as the model provider, but often encountered the problem of model overload, so I tried to modify the configuration to GCP Vertex AI. Then the strange thing happened. When I re-added Google Gemini as the provider and enabled it, it always reported an error: Gemini Generation Context Stream Error: urlContext parameter is not supported in Vertex AI. I understand that this parameter is not supported in Vertex AI, but my question is why it is using my Vertex AI configuration

💥 Outcome Summary

Expected Behavior

When the "Google Gemini" provider is selected and enabled, all subsequent API requests should be routed directly to the Google Gemini API endpoint. These requests should use parameters valid for the Gemini API (like urlContext) and should be completely independent of any previous Vertex AI configuration.

Actual Behavior

After re-enabling the "Google Gemini" provider, the application fails with the following error:
Gemini 生成上下文流错误：urlContext parameter is not supported in Vertex AI.

📄 Relevant Logs or Errors (Optional)

[roomote]

I'm exploring a potential fix for this issue where Google Gemini requests are incorrectly routed to Vertex AI after both providers have been configured. I'll investigate the provider selection logic and open a PR to share progress.

[roomote]

I've opened PR #7969 with a fix for this issue: #7969

The fix prevents the urlContext parameter from being incorrectly added to Vertex AI requests by:

• Adding an isVertex flag to track whether the handler instance is for Vertex AI or regular Gemini
• Only including urlContext in the tools array when it's a regular Gemini instance (not Vertex)

This should resolve the error you were experiencing when switching between Vertex AI and Google Gemini providers. The PR includes comprehensive tests to ensure the fix works correctly for both providers.

[dielect]

I seem to have found the problem because I am using the gemini cli,and my environment variable is set to export GOOGLE_GENAI_USE_VERTEXAI=true.

Because even though I selected google gemini in roo code, it still seems to use Vertex AI.