fix(acp): update auth handshake to spec

[skeshive]

Summary

• Allows client to pass in _meta.apiKey field for Gemini API key auth type
• Propagates agentInfo in initialize request
• Returns correct error code (-32000) when auth is not specified
• Fixes bug where Zed oauth was broken due to requiring user consent for opening browser (ACP protocol does not support this flow)

Will add support for JB AI auth type in a follow-up PR

Related Issues

https://github.com/google-gemini/maintainers-gemini-cli/issues/1329

[gemini-cli]

Hi @skeshive, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[gemini-code-assist]

Summary of Changes

Hello @skeshive, 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 refines the authentication handshake within the Agent Client Protocol (ACP) integration, enhancing how API keys are handled and ensuring proper agent information is communicated during initialization. It also addresses a critical bug in the Zed OAuth flow, streamlining the authentication experience by removing an unsupported user consent step. These changes collectively improve the robustness and compliance of the authentication mechanisms.

Highlights

• Authentication Handshake Updates: The authentication process has been updated to align with the Agent Client Protocol (ACP) specification, allowing clients to pass an _meta.apiKey field for Gemini API key authentication.
• Agent Information Propagation: The agentInfo (including name, title, and version) is now propagated in the initialize request, providing more context about the client agent.
• Standardized Error Handling: Error handling for authentication failures has been standardized to return the correct ACP error code (-32000) when authentication is not specified or fails.
• Zed OAuth Flow Fix: A bug in the Zed OAuth flow was resolved by modifying the process to no longer require explicit user consent for opening the browser, as this flow is not supported by the ACP protocol.

Activity

• No human activity has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

The pull request correctly implements the ACP authentication handshake updates, including support for passing an API key via metadata and propagating agent information. It also addresses a bug in the Zed integration by skipping interactive consent. However, there is a significant issue where the API key provided during authentication is not propagated to new sessions, which will cause authentication failures. Additionally, there are some formatting inconsistencies in the imports in packages/core/src/config/config.ts that violate the project's style guide.

[github-actions]

Size Change: +725 B (0%)

Total Size: 25.7 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.3 MB	+725 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	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-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

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