fix(core): ensure subagent tool updates apply configuration overrides immediately

[abhipatel12]

Summary

Fixes two related issues with subagent configuration during a running session:

1. Subagents were not unregistered when disabled via agents.overrides (like in settings.json or via /agents).
2. Configuration changes (such as selecting a different model or changing temperature) were not applied to already-enabled subagents without a restart.

When a session reloads settings, the Config.registerSubAgentTools method was correctly skipping the addition of disabled subagents, but failed to explicitly remove them from the ToolRegistry. Furthermore, it was using base, unmerged definitions to construct SubagentTool instances, ignoring any user-specified overrides.

Details

• Updated registerSubAgentTools in packages/core/src/config/config.ts to use getAllDiscoveredAgentNames() to explicitly unregister any subagents that are now disabled.
• Updated registerSubAgentTools to use getRegisteredAgents() (which returns merged definitions) when constructing SubagentTool instances, ensuring all configuration overrides are applied immediately.
• Added unit tests to packages/core/src/config/config.test.ts to simulate a "live reload" scenario and guarantee this behavior.

Related Issues

N/A

How to Validate

1. Enable a subagent (e.g. codebase_investigator) in settings.json.
2. Disable it while the session is running (either by editing settings.json or via /agents).
3. Verify that the agent tool is no longer available in the session.
4. Re-enable the subagent and change its model in the /agents config.
5. Verify that the subagent now uses the newly configured model without needing a restart.

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, 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 addresses a critical bug where disabling subagents during an active session did not lead to their corresponding tools being unregistered. The changes ensure that when agent configurations are reloaded, any subagents that have been disabled are properly removed from the system's tool registry, preventing stale or unauthorized tools from remaining active. This improves the dynamic configuration management of agents and maintains system integrity.

Highlights

• Subagent Unregistration Fix: Resolved an issue where subagents were not being unregistered as tools when disabled via agents.overrides during a running session, ensuring that disabled tools are properly removed from the ToolRegistry.
• Configuration Reload Handling: The registerSubAgentTools method in config.ts was updated to explicitly unregister subagent tools that are flagged as enabled: false when settings are reloaded.
• New Unit Test: A new unit test was added to config.test.ts to simulate a 'live reload' scenario, verifying that subagents are correctly unregistered when disabled after being previously enabled.

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[github-actions]

Size Change: +531 B (0%)

Total Size: 26.1 MB

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[gemini-code-assist]

Code Review

This pull request effectively addresses the issue of subagents not being unregistered when disabled during a session. The addition of an explicit unregistration step in registerSubAgentTools ensures that the ToolRegistry accurately reflects the enabled state of agents. The new unit test provides good coverage for this scenario, simulating a live reload and verifying the correct unregistration behavior. The documentation updates are minor clarifications.

[abhipatel12]

/gemini review

[gemini-code-assist]

Code Review

This pull request effectively addresses the issues of subagent unregistration and immediate application of configuration overrides. However, it introduces a potential Denial of Service (DoS) vulnerability where the new logic for unregistering disabled agents can incorrectly remove built-in tools if agent names collide, leading to a loss of core functionality. Additionally, the new unit test in packages/core/src/config/config.test.ts deviates from repository testing conventions by manipulating environment variables and private class properties, which should be addressed for improved reliability and maintainability.

[abhipatel12]

/gemini review

[gemini-code-assist]

Code Review

This pull request correctly addresses two issues related to subagent configuration reloading. The changes ensure that subagents are properly unregistered when disabled and that any configuration updates for enabled subagents are applied immediately without requiring a session restart. This is achieved by adding an explicit unregistration step and re-running the registration logic with the latest merged configurations during a settings reload. A new unit test has been added to validate the unregistration behavior, which is a good addition. The implementation is sound and effectively resolves the described problems.

[NTaylorMullen]

Approving to unblock, would suggest applying the comments though