gemini-cli/docs/cli/gemma4-routing.md

Gemma 4 Routing

Gemini CLI allows you to seamlessly route your requests to Gemma 4 models. When enabled, requests that would normally be sent to standard Gemini Pro and Flash models are automatically redirected to your chosen Gemma 4 variant.

Configuration

You can enable Gemma 4 routing using the CLI settings or by modifying your settings.json file.

Via Settings UI

1. Open the settings dialog by running /settings.
2. Navigate to the Model section.
3. Locate the Gemma 4 Variant setting.
4. Select your preferred model:
   • gemma-4-26b-a4b-it (Gemma 4 26B A4B IT)
   • gemma-4-31b-it (Gemma 4 31B IT)
5. Save the settings and restart the CLI if prompted.

Via settings.json

You can also set this directly in your .gemini/settings.json file:

{
  "model": {
    "gemma4Variant": "gemma-4-31b-it"
  }
}

How it works

When a gemma4Variant is selected, Gemini CLI intercepts model resolution:

• Requests for gemini-pro, gemini-flash, and their associated aliases (like auto, pro, flash) are routed to the selected Gemma 4 model.
• The router model (flash-lite) remains unaffected and continues to use gemini-2.5-flash-lite. This ensures fast, lightweight background routing tasks continue to operate optimally.
• If you do not have preview model access, the CLI normally falls back to stable models; however, the Gemma 4 variant will still take precedence for Pro and Flash targets.

To disable Gemma 4 routing, simply remove the gemma4Variant configuration from your settings or set it to undefined/empty in the UI.