Implement support for subagents as extensions. (#16473)

packages/core/src/agents/registry.test.ts

@@ -8,7 +8,7 @@ import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import { AgentRegistry, getModelConfigAlias } from './registry.js';
 import { makeFakeConfig } from '../test-utils/config.js';
 import type { AgentDefinition, LocalAgentDefinition } from './types.js';
-import type { Config } from '../config/config.js';
+import type { Config, GeminiCLIExtension } from '../config/config.js';
 import { debugLogger } from '../utils/debugLogger.js';
 import { coreEvents, CoreEvent } from '../utils/events.js';
 import { A2AClientManager } from './a2a-client-manager.js';
@@ -20,6 +20,7 @@ import {
   PREVIEW_GEMINI_MODEL_AUTO,
 } from '../config/models.js';
 import * as tomlLoader from './agentLoader.js';
+import { SimpleExtensionLoader } from '../utils/extensionLoader.js';
 
 vi.mock('./agentLoader.js', () => ({
   loadAgentsFromDirectory: vi
@@ -230,7 +231,7 @@ describe('AgentRegistry', () => {
       expect(registry.getDefinition('cli_help')).toBeDefined();
     });
 
-    it('should NOT register CLI help agent if disabled', async () => {
+    it('should register CLI help agent if disabled', async () => {
       const config = makeFakeConfig({
         cliHelpAgentSettings: { enabled: false },
       });
@@ -240,6 +241,59 @@ describe('AgentRegistry', () => {
 
       expect(registry.getDefinition('cli_help')).toBeUndefined();
     });
+
+    it('should load agents from active extensions', async () => {
+      const extensionAgent = {
+        ...MOCK_AGENT_V1,
+        name: 'extension-agent',
+      };
+      const extensions: GeminiCLIExtension[] = [
+        {
+          name: 'test-extension',
+          isActive: true,
+          agents: [extensionAgent],
+          version: '1.0.0',
+          path: '/path/to/extension',
+          contextFiles: [],
+          id: 'test-extension-id',
+        },
+      ];
+      const mockConfig = makeFakeConfig({
+        extensionLoader: new SimpleExtensionLoader(extensions),
+        enableAgents: true,
+      });
+      const registry = new TestableAgentRegistry(mockConfig);
+
+      await registry.initialize();
+
+      expect(registry.getDefinition('extension-agent')).toEqual(extensionAgent);
+    });
+
+    it('should NOT load agents from inactive extensions', async () => {
+      const extensionAgent = {
+        ...MOCK_AGENT_V1,
+        name: 'extension-agent',
+      };
+      const extensions: GeminiCLIExtension[] = [
+        {
+          name: 'test-extension',
+          isActive: false,
+          agents: [extensionAgent],
+          version: '1.0.0',
+          path: '/path/to/extension',
+          contextFiles: [],
+          id: 'test-extension-id',
+        },
+      ];
+      const mockConfig = makeFakeConfig({
+        extensionLoader: new SimpleExtensionLoader(extensions),
+      });
+      const registry = new TestableAgentRegistry(mockConfig);
+
+      await registry.initialize();
+
+      expect(registry.getDefinition('extension-agent')).toBeUndefined();
+    });
   });
 
   describe('registration logic', () => {

packages/core/src/agents/registry.ts

@@ -14,6 +14,7 @@ import { CliHelpAgent } from './cli-help-agent.js';
 import { A2AClientManager } from './a2a-client-manager.js';
 import { ADCHandler } from './remote-invocation.js';
 import { type z } from 'zod';
+import type { GenerateContentConfig } from '@google/genai';
 import { debugLogger } from '../utils/debugLogger.js';
 import {
   DEFAULT_GEMINI_MODEL,
@@ -120,6 +121,15 @@ export class AgentRegistry {
       );
     }
 
+    // Load agents from extensions
+    for (const extension of this.config.getExtensions()) {
+      if (extension.isActive && extension.agents) {
+        await Promise.allSettled(
+          extension.agents.map((agent) => this.registerAgent(agent)),
+        );
+      }
+    }
+
     if (this.config.getDebugMode()) {
       debugLogger.log(
         `[AgentRegistry] Loaded with ${this.agents.size} agents.`,
@@ -233,7 +243,7 @@ export class AgentRegistry {
       model = this.config.getModel();
     }
 
-    const generateContentConfig = {
+    const generateContentConfig: GenerateContentConfig = {
       temperature: modelConfig.temp,
       topP: modelConfig.top_p,
       thinkingConfig: {

packages/core/src/config/config.ts

@@ -101,6 +101,7 @@ import { ExperimentFlags } from '../code_assist/experiments/flagNames.js';
 import { debugLogger } from '../utils/debugLogger.js';
 import { SkillManager, type SkillDefinition } from '../skills/skillManager.js';
 import { startupProfiler } from '../telemetry/startupProfiler.js';
+import type { AgentDefinition } from '../agents/types.js';
 
 export interface AccessibilitySettings {
   disableLoadingPhrases?: boolean;
@@ -178,6 +179,7 @@ export interface GeminiCLIExtension {
   settings?: ExtensionSetting[];
   resolvedSettings?: ResolvedExtensionSetting[];
   skills?: SkillDefinition[];
+  agents?: AgentDefinition[];
 }
 
 export interface ExtensionInstallMetadata {

packages/core/src/index.ts

@@ -126,6 +126,7 @@ export * from './prompts/mcp-prompts.js';
 
 // Export agent definitions
 export * from './agents/types.js';
+export * from './agents/agentLoader.js';
 
 // Export specific tool logic
 export * from './tools/read-file.js';