fix(core): add proxy routing support for remote A2A subagents

[adamfweidman]

Summary

Adds proxy routing support for remote A2A subagents.

Details

The A2AClientManager's dispatcher was previously initialized outside of the class instance context, bypassing the globally configured proxy URL inside gemini-cli. This fix updates the client manager to accept a Config instance and evaluate config.getProxy().

If a proxy URL is found, it instantiates an undici ProxyAgent using the proxy URL, explicitly scoping it for A2A connections. It preserves the 30-minute high-timeout requirement for remote agents (e.g., Deep Research) and uses safeLookup to maintain SSRF mitigation.

Related Issues

Fixes #20303

How to Validate

1. Start gemini-cli with a proxy configured (http_proxy / https_proxy or general.proxy setting).
2. Call a remote A2A subagent and monitor the proxy logs.
3. Validate that the traffic is reliably routed through the proxy.
4. Run npm run preflight to confirm existing test behavior remains passing.

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-cli]

Hi @adamfweidman, 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-cli]

Hi there! Thank you for your contribution to Gemini CLI.

To improve our contribution process and better track changes, we now require all pull requests to be associated with an existing issue, as announced in our recent discussion and as detailed in our CONTRIBUTING.md.

This pull request is being closed because it is not currently linked to an issue. Once you have updated the description of this PR to link an issue (e.g., by adding Fixes #123 or Related to #123), it will be automatically reopened.

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[gemini-code-assist]

Summary of Changes

Hello, 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 enhances the A2AClientManager to properly handle proxy configurations for remote agent-to-agent communication. By refactoring the dispatcher initialization to be instance-specific and configurable via a Config object, it ensures that all A2A network requests are routed through the designated proxy when one is present. This change improves network compatibility and security for agent interactions within the system.

Highlights

• Proxy Routing for A2A Subagents: Added support for proxy routing for remote A2A subagents, ensuring that agent-to-agent communication respects globally configured proxy settings.
• Dynamic Dispatcher Initialization: The A2AClientManager now accepts a Config instance, allowing it to dynamically initialize either an UndiciAgent or an undici.ProxyAgent based on whether a proxy URL is configured.
• SSRF Mitigation and Timeout Preservation: The ProxyAgent instantiation explicitly scopes A2A connections, preserves the 30-minute high-timeout requirement for remote agents, and continues to use safeLookup for SSRF mitigation.
• Test Coverage: New test cases were added to a2a-client-manager.test.ts to validate the correct dispatcher (UndiciAgent or ProxyAgent) is used based on proxy configuration.

Changelog

• packages/core/src/agents/a2a-client-manager.test.ts
  • Added imports for Config and ProxyAgent.
  • Introduced new test suites to verify UndiciAgent usage when no proxy is configured.
  • Added new test suites to verify ProxyAgent usage when a proxy is configured via Config.
• packages/core/src/agents/a2a-client-manager.ts
  • Removed the global a2aDispatcher and a2aFetch constants.
  • Modified the A2AClientManager constructor to accept an optional Config object.
  • Implemented logic within the constructor to initialize a2aDispatcher as either UndiciAgent or ProxyAgent based on the config.getProxy() value.
  • Updated getInstance method to accept an optional Config parameter, passing it to the constructor.
  • Updated authFetch and a2aFetch calls to use the instance-specific this.a2aFetch.
• packages/core/src/agents/registry.ts
  • Modified calls to A2AClientManager.getInstance() in reload() and agent loading logic to pass this.config.

Activity

• The pull request was authored by adamfweidman.
• The author provided a detailed summary, specific implementation details, and clear validation steps.
• The author confirmed that tests were added/updated and validated the changes on MacOS using npm run.

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[gemini-cli]

Thank you for linking an issue! This pull request has been automatically reopened.

[adamfweidman]

/gemini review

[github-actions]

Size Change: +439 B (0%)

Total Size: 26.6 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	26.1 MB	+439 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

_{compressed-size-action}

[gemini-code-assist]

Code Review

This pull request correctly adds proxy support for A2A subagents by passing the Config object to the A2AClientManager and using it to instantiate a ProxyAgent when a proxy URL is configured. The implementation preserves existing timeouts and security measures, and the new logic is well-tested. I have one suggestion to refactor the agent dispatcher initialization to reduce code duplication and improve long-term maintainability.

[gemini-code-assist]

Code Review

This pull request correctly adds proxy support for A2A subagents by refactoring A2AClientManager to be aware of the application's Config. However, it inadvertently bypasses the existing SSRF (Server-Side Request Forgery) mitigation. The safeLookup mechanism used for SSRF protection is ineffective when a ProxyAgent is employed, as the proxy handles DNS resolution for the target host, potentially allowing SSRF attacks against internal networks if a malicious agent definition is loaded. A fix is recommended to validate target URLs before they are passed to the proxy-enabled dispatcher. Additionally, there is an opportunity to improve maintainability by reducing code duplication.

[gsquared94]

LGTM!