use previewFeatures to determine which pro model to use for A2A

[sehoon38]

Summary

Use previewFeatures to pick which pro model to use for A2A.

Details

A2A currently doesn't use Gemini 3 model, and this exposes a way to pick either Gemini 3 pro or Gemini 2.5 pro model depending on the previewFeatures settings.

Related Issues

How to Validate

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello @sehoon38, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a mechanism to control which Gemini Pro model is utilized by the A2A system. By leveraging the previewFeatures setting, the system can now switch between different Gemini Pro versions, enabling early access to newer models for A2A functionalities. This change allows for more flexible model deployment and testing within the A2A framework.

Highlights

• Dynamic Gemini Model Selection: The A2A system will now dynamically select the Gemini Pro model based on the previewFeatures setting. If previewFeatures is enabled, PREVIEW_GEMINI_MODEL (Gemini 3 Pro) will be used; otherwise, DEFAULT_GEMINI_MODEL (Gemini 2.5 Pro) will be used.

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[github-actions]

Size Change: -2 B (0%)

Total Size: 21.6 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	21.6 MB	-2 B (0%)
./bundle/sandbox-macos-permissive-closed.sb	1.03 kB	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-closed.sb	3.29 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B

_{compressed-size-action}

[gemini-code-assist]

Code Review

This pull request updates the A2A server configuration to select the Gemini model based on the previewFeatures setting. The implementation correctly uses the setting from the configuration file. However, I've identified a potential issue where previewFeatures enabled remotely via experiments after authentication would not be respected for model selection. I've left a comment with a suggestion to fix this by re-evaluating the model after authentication is refreshed. This will ensure the logic is robust and respects both local and remote configurations.

[scidomino]

/patch preview

[github-actions]

✅ Patch workflow(s) dispatched successfully!

📋 Details:

• Channels: preview
• Commit: 2995af6a21c68147823aec0587cb19330a9aeee8
• Workflows Created: 1

🔗 Track Progress:

• View patch workflows
• This workflow run

[github-actions]

🚀 Patch PR Created!

📋 Patch Details:

• Environment: prod
• Channel: preview → will publish to npm tag preview
• Commit: 2995af6a21c68147823aec0587cb19330a9aeee8
• Hotfix Branch: hotfix/v0.21.0-preview.5/0.21.0-preview.6/preview/cherry-pick-2995af6/pr-15131
• Hotfix PR: #15153

📝 Next Steps:

1. Review and approve the hotfix PR: #15153
2. Once merged, the patch release will automatically trigger
3. You'll receive updates here when the release completes

🔗 Track Progress:

• View hotfix PR #15153

[github-actions]

🚀 Patch Release Started!

📋 Release Details:

• Environment: prod
• Channel: preview → publishing to npm tag preview
• Version: v0.21.0-preview.5
• Hotfix PR: Merged ✅
• Release Branch: release/v0.21.0-preview.5-pr-15131

⏳ Status: The patch release is now running. You'll receive another update when it completes.

🔗 Track Progress:

• View release workflow

[github-actions]

✅ Patch Release Complete!

📦 Release Details:

• Version: 0.21.0-preview.6
• NPM Tag: preview
• Channel: preview
• Dry Run: false

🎉 Status: Your patch has been successfully released and published to npm!

📝 What's Available:

• GitHub Release: View release v0.21.0-preview.6
• NPM Package: npm install @google/gemini-cli@preview

🔗 Links:

• GitHub Release
• Workflow Run