feat: Add `enableSubagents` configuration and wire up subagent registration #9988

abhipatel12 · 2025-09-26T20:09:02Z

TLDR

This PR introduces the necessary configuration and wiring to enable the experimental "Subagents" feature. It adds a new enableSubagents setting, updates the core Config to dynamically register subagents as tools when this setting is enabled, and ensures the MessageBus is correctly propagated for policy enforcement. It also resolves a circular dependency that was exposed by these changes.

Dive Deeper

Configuration Changes

Added a new boolean setting experimental.enableSubagents to the CLI settingsSchema. It defaults to false and requires a restart to take effect.
Updated both the CLI and Core Config classes to read and expose this setting.

Subagent Registration

In packages/core/src/config/config.ts, an AgentRegistry is now initialized.
The createToolRegistry method has been updated. If enableSubagents is true, it retrieves all agent definitions from the registry, wraps them in a SubagentToolWrapper, and registers them as tools.
This registration process respects the existing allowedTools and excludeTools configuration, allowing users to control which subagents are available.

Message Bus Propagation

Updated SubagentToolWrapper and SubagentInvocation to accept an optional MessageBus in their constructors.
The Config class now passes the MessageBus when creating the SubagentToolWrapper. This ensures that any actions taken by the subagents will still participate in the standard confirmation and policy enforcement flow.

Circular Dependency Fix

The introduction of AgentRegistry into Config exposed a circular dependency:
Config -> AgentRegistry -> CodebaseInvestigatorAgent -> GlobTool -> Config.

This was causing glob.test.ts to fail. The fix involved decoupling the tool name from the tool implementation:

Created packages/core/src/tools/tool-names.ts to hold tool name constants.
Updated GlobTool to use the constant GLOB_TOOL_NAME.
Updated CodebaseInvestigatorAgent to import the name from tool-names.ts instead of importing the GlobTool class, thus breaking the import cycle.

Reviewer Test Plan

1. Verify Unit Tests

Run preflight and ensure all tests pass

2. Verify Configuration Behavior

Start the CLI without modifying settings. Verify that subagents are not loaded (you can check /tools to see if you see the example codebase investigator).

Open your settings file and add:

"experimental": {
  "enableSubagents": true
}

Restart the CLI. Verify that the codebase investigator is being registered now.

Testing Matrix

	🍏	🪟	🐧
npm run	✅	❓	❓
npx	❓	❓	❓
Docker	❓	❓	❓
Podman	❓	-	-
Seatbelt	✅	-	-

gemini-code-assist · 2025-09-26T20:09:28Z

Summary of Changes

Hello @abhipatel12, 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 lays the foundational groundwork for integrating experimental subagents into the system. It introduces a new configuration option to enable this feature, sets up the necessary infrastructure for subagents to be recognized and utilized as tools, and ensures their operations adhere to existing policy enforcement mechanisms. A significant architectural improvement was also made by resolving a critical circular dependency, enhancing the modularity and stability of the codebase.

Highlights

Subagent Configuration and Registration: Introduced a new experimental setting, enableSubagents, which, when enabled, dynamically registers defined subagents as tools within the core Config.
Message Bus Integration for Subagents: Ensured that the MessageBus is correctly propagated to SubagentToolWrapper and SubagentInvocation to facilitate policy enforcement and confirmation flows for subagent actions.
Circular Dependency Resolution: Fixed a circular dependency involving Config, AgentRegistry, CodebaseInvestigatorAgent, and GlobTool by decoupling tool names from their implementations using a new tool-names.ts module.
New Subagent Module: Added a comprehensive new module for subagents, including AgentExecutor for running agent loops, AgentRegistry for managing agent definitions, SubagentInvocation for tool execution, and SubagentToolWrapper to expose subagents as standard tools.

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Code Review

This pull request introduces the foundational components for the experimental "Subagents" feature. The changes are well-structured, adding a new configuration flag enableSubagents and the necessary logic in the Config class to dynamically register agent definitions as tools. The implementation of the AgentExecutor is robust, with good separation of concerns and important security considerations like an allowlist for non-interactive tools and runtime authorization checks. The introduction of a new AgentRegistry and the SubagentToolWrapper provides a clean abstraction for this new capability. Additionally, the PR thoughtfully addresses and resolves a circular dependency that was exposed by these changes. The new test suites for the agent components are comprehensive and cover many edge cases.

My review identifies one high-severity issue related to the generation of fallback IDs for tool calls, which could lead to collisions and incorrect agent behavior in rare but possible scenarios. A fix is suggested to ensure unique ID generation. Overall, this is a solid contribution that lays the groundwork for a powerful new feature.

packages/core/src/agents/executor.ts

github-actions · 2025-09-26T20:10:47Z

Size Change: +39.2 kB (+0.22%)

Total Size: 17.5 MB

Filename	Size	Change
`./bundle/gemini.js`	17.5 MB	+39.2 kB (+0.22%)

ℹ️ View Unchanged

Filename	Size
`./bundle/sandbox-macos-permissive-closed.sb`	1.03 kB
`./bundle/sandbox-macos-permissive-open.sb`	830 B
`./bundle/sandbox-macos-permissive-proxied.sb`	1.31 kB
`./bundle/sandbox-macos-restrictive-closed.sb`	3.29 kB
`./bundle/sandbox-macos-restrictive-open.sb`	3.36 kB
`./bundle/sandbox-macos-restrictive-proxied.sb`	3.56 kB

_{compressed-size-action}

silviojr · 2025-10-01T03:16:01Z

packages/cli/src/config/config.ts

    useModelRouter,
    enableMessageBusIntegration:
      settings.tools?.enableMessageBusIntegration ?? false,
+    enableSubagents: settings.experimental?.enableSubagents ?? false,


I think this should be fine for now, but it would be great to have a list where you list the subagents you want to enable.

Yeah that sounds great! I think as we discover a need for it, we can add more properties

silviojr · 2025-10-01T03:21:48Z

packages/core/src/config/config.ts

+      for (const definition of agentDefinitions) {
+        // We must respect the main allowed/exclude lists for agents too.
+        const excludeTools = this.getExcludeTools() || [];
+        const allowedTools = this.getAllowedTools();


Hmm.. ok. So instead of having a list of enabled agents we are explicit considering them as tools and having the list of allowed/excluded here.

Yeah, in the event that a user says they want to disable a subagent, we would need to respect that. For now, since we don't have a special flag --disable-subagent, we can respect it via the tool flag list.

packages/core/src/tools/tool-names.ts

- Adds `enableSubagents` to CLI and Core configuration. - Updates `settingsSchema` to include the new setting. - Updates `Config` in core to register subagents as tools when enabled. - Updates `SubagentToolWrapper` and `AgentInvocation` to propagate the `messageBus`. - Adds comprehensive tests for all new functionality. - Fixes a circular dependency between `Config` and `GlobTool` by extracting the tool name to a new `tool-names.ts` constants file.

…t registration (google-gemini#9988)

…ration (google-gemini#9988)

abhipatel12 requested a review from a team as a code owner September 26, 2025 20:09

gemini-code-assist bot reviewed Sep 26, 2025

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packages/core/src/agents/executor.ts Outdated Show resolved Hide resolved

abhipatel12 force-pushed the abhipatel12/add-agent-configuration branch from 047283f to 4b167da Compare September 29, 2025 17:07

silviojr reviewed Oct 1, 2025

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packages/core/src/tools/tool-names.ts Show resolved Hide resolved

silviojr approved these changes Oct 1, 2025

View reviewed changes

abhipatel12 force-pushed the abhipatel12/add-agent-configuration branch from 4b167da to e7fbf64 Compare October 1, 2025 20:41

abhipatel12 added this pull request to the merge queue Oct 1, 2025

Merged via the queue into main with commit 331ae7d Oct 1, 2025
24 of 26 checks passed

abhipatel12 deleted the abhipatel12/add-agent-configuration branch October 1, 2025 20:55

thacio added a commit to thacio/auditaria that referenced this pull request Oct 6, 2025

Merge Commit '331ae7d': feat: Add \ configuration and wire up subagen…

01b6833

…t registration (google-gemini#9988)

giraffe-tree pushed a commit to giraffe-tree/gemini-cli that referenced this pull request Oct 10, 2025

feat: Add enableSubagents configuration and wire up subagent regist…

215aca1

…ration (google-gemini#9988)

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abhipatel12 commented Sep 26, 2025

TLDR

Dive Deeper

Configuration Changes

Subagent Registration

Message Bus Propagation

Circular Dependency Fix

Reviewer Test Plan

1. Verify Unit Tests

2. Verify Configuration Behavior

Testing Matrix

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