feat(core): subagent local execution and tool isolation (#22718)

packages/core/src/agents/agent-scheduler.test.ts

@@ -42,6 +42,8 @@ describe('agent-scheduler', () => {
 
   it('should create a scheduler with agent-specific config', async () => {
     const mockConfig = {
+      getPromptRegistry: vi.fn(),
+      getResourceRegistry: vi.fn(),
       messageBus: mockMessageBus,
       toolRegistry: mockToolRegistry,
     } as unknown as Mocked<Config>;
@@ -91,6 +93,8 @@ describe('agent-scheduler', () => {
     } as unknown as Mocked<ToolRegistry>;
 
     const config = {
+      getPromptRegistry: vi.fn(),
+      getResourceRegistry: vi.fn(),
       messageBus: mockMessageBus,
     } as unknown as Mocked<Config>;
     Object.defineProperty(config, 'toolRegistry', {
@@ -123,6 +127,8 @@ describe('agent-scheduler', () => {
 
   it('should create an AgentLoopContext that has a defined .config property', async () => {
     const mockConfig = {
+      getPromptRegistry: vi.fn(),
+      getResourceRegistry: vi.fn(),
       messageBus: mockMessageBus,
       toolRegistry: mockToolRegistry,
       promptId: 'test-prompt',

packages/core/src/agents/agent-scheduler.ts

@@ -11,6 +11,8 @@ import type {
   CompletedToolCall,
 } from '../scheduler/types.js';
 import type { ToolRegistry } from '../tools/tool-registry.js';
+import type { PromptRegistry } from '../prompts/prompt-registry.js';
+import type { ResourceRegistry } from '../resources/resource-registry.js';
 import type { EditorType } from '../utils/editor.js';
 
 /**
@@ -25,6 +27,10 @@ export interface AgentSchedulingOptions {
   parentCallId?: string;
   /** The tool registry specific to this agent. */
   toolRegistry: ToolRegistry;
+  /** The prompt registry specific to this agent. */
+  promptRegistry?: PromptRegistry;
+  /** The resource registry specific to this agent. */
+  resourceRegistry?: ResourceRegistry;
   /** AbortSignal for cancellation. */
   signal: AbortSignal;
   /** Optional function to get the preferred editor for tool modifications. */
@@ -51,16 +57,19 @@ export async function scheduleAgentTools(
     subagent,
     parentCallId,
     toolRegistry,
+    promptRegistry,
+    resourceRegistry,
     signal,
     getPreferredEditor,
     onWaitingForConfirmation,
   } = options;
 
-  // Create a proxy/override of the config to provide the agent-specific tool registry.
   const schedulerContext = {
     config,
     promptId: config.promptId,
     toolRegistry,
+    promptRegistry: promptRegistry ?? config.getPromptRegistry(),
+    resourceRegistry: resourceRegistry ?? config.getResourceRegistry(),
     messageBus: toolRegistry.messageBus,
     geminiClient: config.geminiClient,
     sandboxManager: config.sandboxManager,

packages/core/src/agents/local-executor.test.ts

@@ -13,10 +13,43 @@ import {
   afterEach,
   type Mock,
 } from 'vitest';
+
+const {
+  mockSendMessageStream,
+  mockScheduleAgentTools,
+  mockSetSystemInstruction,
+  mockCompress,
+  mockMaybeDiscoverMcpServer,
+  mockStopMcp,
+} = vi.hoisted(() => ({
+  mockSendMessageStream: vi.fn().mockResolvedValue({
+    async *[Symbol.asyncIterator]() {
+      yield {
+        type: 'chunk',
+        value: { candidates: [] },
+      };
+    },
+  }),
+  mockScheduleAgentTools: vi.fn(),
+  mockSetSystemInstruction: vi.fn(),
+  mockCompress: vi.fn(),
+  mockMaybeDiscoverMcpServer: vi.fn().mockResolvedValue(undefined),
+  mockStopMcp: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock('../tools/mcp-client-manager.js', () => ({
+  McpClientManager: class {
+    maybeDiscoverMcpServer = mockMaybeDiscoverMcpServer;
+    stop = mockStopMcp;
+  },
+}));
+
 import { debugLogger } from '../utils/debugLogger.js';
 import { LocalAgentExecutor, type ActivityCallback } from './local-executor.js';
 import { makeFakeConfig } from '../test-utils/config.js';
 import { ToolRegistry } from '../tools/tool-registry.js';
+import { PromptRegistry } from '../prompts/prompt-registry.js';
+import { ResourceRegistry } from '../resources/resource-registry.js';
 import { DiscoveredMCPTool } from '../tools/mcp-tool.js';
 import { LSTool } from '../tools/ls.js';
 import { LS_TOOL_NAME, READ_FILE_TOOL_NAME } from '../tools/tool-names.js';
@@ -70,18 +103,6 @@ import type {
 import { getModelConfigAlias, type AgentRegistry } from './registry.js';
 import type { ModelRouterService } from '../routing/modelRouterService.js';
 
-const {
-  mockSendMessageStream,
-  mockScheduleAgentTools,
-  mockSetSystemInstruction,
-  mockCompress,
-} = vi.hoisted(() => ({
-  mockSendMessageStream: vi.fn(),
-  mockScheduleAgentTools: vi.fn(),
-  mockSetSystemInstruction: vi.fn(),
-  mockCompress: vi.fn(),
-}));
-
 let mockChatHistory: Content[] = [];
 const mockSetHistory = vi.fn((newHistory: Content[]) => {
   mockChatHistory = newHistory;
@@ -2722,6 +2743,67 @@ describe('LocalAgentExecutor', () => {
     });
   });
 
+  describe('MCP Isolation', () => {
+    it('should initialize McpClientManager when mcpServers are defined', async () => {
+      const { MCPServerConfig } = await import('../config/config.js');
+      const mcpServers = {
+        'test-server': new MCPServerConfig('node', ['server.js']),
+      };
+
+      const definition = {
+        ...createTestDefinition(),
+        mcpServers,
+      };
+
+      vi.spyOn(mockConfig, 'getMcpClientManager').mockReturnValue({
+        maybeDiscoverMcpServer: mockMaybeDiscoverMcpServer,
+      } as unknown as ReturnType<typeof mockConfig.getMcpClientManager>);
+
+      await LocalAgentExecutor.create(definition, mockConfig);
+
+      const mcpManager = mockConfig.getMcpClientManager();
+      expect(mcpManager?.maybeDiscoverMcpServer).toHaveBeenCalledWith(
+        'test-server',
+        mcpServers['test-server'],
+        expect.objectContaining({
+          toolRegistry: expect.any(ToolRegistry),
+          promptRegistry: expect.any(PromptRegistry),
+          resourceRegistry: expect.any(ResourceRegistry),
+        }),
+      );
+    });
+
+    it('should inherit main registry tools', async () => {
+      const parentMcpTool = new DiscoveredMCPTool(
+        {} as unknown as CallableTool,
+        'main-server',
+        'tool1',
+        'desc1',
+        {},
+        mockConfig.getMessageBus(),
+      );
+
+      parentToolRegistry.registerTool(parentMcpTool);
+
+      const definition = createTestDefinition();
+      definition.toolConfig = undefined; // trigger inheritance
+
+      vi.spyOn(mockConfig, 'getMcpClientManager').mockReturnValue({
+        maybeDiscoverMcpServer: vi.fn(),
+      } as unknown as ReturnType<typeof mockConfig.getMcpClientManager>);
+      const executor = await LocalAgentExecutor.create(
+        definition,
+        mockConfig,
+        onActivity,
+      );
+      const agentTools = (
+        executor as unknown as { toolRegistry: ToolRegistry }
+      ).toolRegistry.getAllToolNames();
+
+      expect(agentTools).toContain(parentMcpTool.name);
+    });
+  });
+
   describe('DeclarativeTool instance tools (browser agent pattern)', () => {
     /**
      * The browser agent passes DeclarativeTool instances (not string names) in
@@ -2827,13 +2909,11 @@ describe('LocalAgentExecutor', () => {
       const navTool = new MockTool({ name: 'navigate_page' });
 
       const definition = createInstanceToolDefinition([clickTool, navTool]);
-
       const executor = await LocalAgentExecutor.create(
         definition,
         mockConfig,
         onActivity,
       );
-
       const registry = executor['toolRegistry'];
       expect(registry.getTool('click')).toBeDefined();
       expect(registry.getTool('navigate_page')).toBeDefined();

packages/core/src/agents/local-executor.ts

@@ -4,7 +4,6 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type { Config } from '../config/config.js';
 import { type AgentLoopContext } from '../config/agent-loop-context.js';
 import { reportError } from '../utils/errorReporting.js';
 import { GeminiChat, StreamEventType } from '../core/geminiChat.js';
@@ -17,6 +16,8 @@ import {
   type Schema,
 } from '@google/genai';
 import { ToolRegistry } from '../tools/tool-registry.js';
+import { PromptRegistry } from '../prompts/prompt-registry.js';
+import { ResourceRegistry } from '../resources/resource-registry.js';
 import { type AnyDeclarativeTool } from '../tools/tools.js';
 import {
   DiscoveredMCPTool,
@@ -102,14 +103,22 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
 
   private readonly agentId: string;
   private readonly toolRegistry: ToolRegistry;
+  private readonly promptRegistry: PromptRegistry;
+  private readonly resourceRegistry: ResourceRegistry;
   private readonly context: AgentLoopContext;
   private readonly onActivity?: ActivityCallback;
   private readonly compressionService: ChatCompressionService;
   private readonly parentCallId?: string;
   private hasFailedCompressionAttempt = false;
 
-  private get config(): Config {
-    return this.context.config;
+  private get executionContext(): AgentLoopContext {
+    return {
+      ...this.context,
+      toolRegistry: this.toolRegistry,
+      promptRegistry: this.promptRegistry,
+      resourceRegistry: this.resourceRegistry,
+      messageBus: this.toolRegistry.getMessageBus(),
+    };
   }
 
   /**
@@ -133,11 +142,27 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     // Create an override object to inject the subagent name into tool confirmation requests
     const subagentMessageBus = parentMessageBus.derive(definition.name);
 
-    // Create an isolated tool registry for this agent instance.
+    // Create isolated registries for this agent instance.
     const agentToolRegistry = new ToolRegistry(
       context.config,
       subagentMessageBus,
     );
+    const agentPromptRegistry = new PromptRegistry();
+    const agentResourceRegistry = new ResourceRegistry();
+
+    if (definition.mcpServers) {
+      const globalMcpManager = context.config.getMcpClientManager();
+      if (globalMcpManager) {
+        for (const [name, config] of Object.entries(definition.mcpServers)) {
+          await globalMcpManager.maybeDiscoverMcpServer(name, config, {
+            toolRegistry: agentToolRegistry,
+            promptRegistry: agentPromptRegistry,
+            resourceRegistry: agentResourceRegistry,
+          });
+        }
+      }
+    }
+
     const parentToolRegistry = context.toolRegistry;
     const allAgentNames = new Set(
       context.config.getAgentRegistry().getAllAgentNames(),
@@ -153,7 +178,9 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
         return;
       }
 
-      agentToolRegistry.registerTool(tool);
+      // Clone the tool, so it gets its own state and subagent messageBus
+      const clonedTool = tool.clone(subagentMessageBus);
+      agentToolRegistry.registerTool(clonedTool);
     };
 
     const registerToolByName = (toolName: string) => {
@@ -228,10 +255,12 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     return new LocalAgentExecutor(
       definition,
       context,
-      agentToolRegistry,
       parentPromptId,
-      parentCallId,
+      agentToolRegistry,
+      agentPromptRegistry,
+      agentResourceRegistry,
       onActivity,
+      parentCallId,
     );
   }
 
@@ -244,14 +273,18 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
   private constructor(
     definition: LocalAgentDefinition<TOutput>,
     context: AgentLoopContext,
-    toolRegistry: ToolRegistry,
     parentPromptId: string | undefined,
-    parentCallId: string | undefined,
+    toolRegistry: ToolRegistry,
+    promptRegistry: PromptRegistry,
+    resourceRegistry: ResourceRegistry,
     onActivity?: ActivityCallback,
+    parentCallId?: string,
   ) {
     this.definition = definition;
     this.context = context;
     this.toolRegistry = toolRegistry;
+    this.promptRegistry = promptRegistry;
+    this.resourceRegistry = resourceRegistry;
     this.onActivity = onActivity;
     this.compressionService = new ChatCompressionService();
     this.parentCallId = parentCallId;
@@ -447,7 +480,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     } finally {
       clearTimeout(graceTimeoutId);
       logRecoveryAttempt(
-        this.config,
+        this.context.config,
         new RecoveryAttemptEvent(
           this.agentId,
           this.definition.name,
@@ -495,7 +528,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     const combinedSignal = AbortSignal.any([signal, deadlineTimer.signal]);
 
     logAgentStart(
-      this.config,
+      this.context.config,
       new AgentStartEvent(this.agentId, this.definition.name),
     );
 
@@ -506,7 +539,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
       const augmentedInputs = {
         ...inputs,
         cliVersion: await getVersion(),
-        activeModel: this.config.getActiveModel(),
+        activeModel: this.context.config.getActiveModel(),
         today: new Date().toLocaleDateString(),
       };
 
@@ -528,14 +561,16 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
       // Capture the index of the last hint before starting to avoid re-injecting old hints.
       // NOTE: Hints added AFTER this point will be broadcast to all currently running
       // local agents via the listener below.
-      const startIndex = this.config.injectionService.getLatestInjectionIndex();
-      this.config.injectionService.onInjection(injectionListener);
+      const startIndex =
+        this.context.config.injectionService.getLatestInjectionIndex();
+      this.context.config.injectionService.onInjection(injectionListener);
 
       try {
-        const initialHints = this.config.injectionService.getInjectionsAfter(
-          startIndex,
-          'user_steering',
-        );
+        const initialHints =
+          this.context.config.injectionService.getInjectionsAfter(
+            startIndex,
+            'user_steering',
+          );
         const formattedInitialHints = formatUserHintsForModel(initialHints);
 
         let currentMessage: Content = formattedInitialHints
@@ -606,7 +641,16 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
           }
         }
       } finally {
-        this.config.injectionService.offInjection(injectionListener);
+        this.context.config.injectionService.offInjection(injectionListener);
+
+        const globalMcpManager = this.context.config.getMcpClientManager();
+        if (globalMcpManager) {
+          globalMcpManager.removeRegistries({
+            toolRegistry: this.toolRegistry,
+            promptRegistry: this.promptRegistry,
+            resourceRegistry: this.resourceRegistry,
+          });
+        }
       }
 
       // === UNIFIED RECOVERY BLOCK ===
@@ -719,7 +763,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     } finally {
       deadlineTimer.abort();
       logAgentFinish(
-        this.config,
+        this.context.config,
         new AgentFinishEvent(
           this.agentId,
           this.definition.name,
@@ -742,7 +786,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
       prompt_id,
       false,
       model,
-      this.config,
+      this.context.config,
       this.hasFailedCompressionAttempt,
     );
 
@@ -780,10 +824,11 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     const modelConfigAlias = getModelConfigAlias(this.definition);
 
     // Resolve the model config early to get the concrete model string (which may be `auto`).
-    const resolvedConfig = this.config.modelConfigService.getResolvedConfig({
-      model: modelConfigAlias,
-      overrideScope: this.definition.name,
-    });
+    const resolvedConfig =
+      this.context.config.modelConfigService.getResolvedConfig({
+        model: modelConfigAlias,
+        overrideScope: this.definition.name,
+      });
     const requestedModel = resolvedConfig.model;
 
     let modelToUse: string;
@@ -800,7 +845,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
           signal,
           requestedModel,
         };
-        const router = this.config.getModelRouterService();
+        const router = this.context.config.getModelRouterService();
         const decision = await router.route(routingContext);
         modelToUse = decision.model;
       } catch (error) {
@@ -888,7 +933,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
 
     try {
       return new GeminiChat(
-        this.config,
+        this.executionContext,
         systemInstruction,
         [{ functionDeclarations: tools }],
         startHistory,
@@ -1136,13 +1181,15 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     // Execute standard tool calls using the new scheduler
     if (toolRequests.length > 0) {
       const completedCalls = await scheduleAgentTools(
-        this.config,
+        this.context.config,
         toolRequests,
         {
-          schedulerId: this.agentId,
+          schedulerId: promptId,
           subagent: this.definition.name,
           parentCallId: this.parentCallId,
           toolRegistry: this.toolRegistry,
+          promptRegistry: this.promptRegistry,
+          resourceRegistry: this.resourceRegistry,
           signal,
           onWaitingForConfirmation,
         },
@@ -1277,7 +1324,7 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
     let finalPrompt = templateString(promptConfig.systemPrompt, inputs);
 
     // Append environment context (CWD and folder structure).
-    const dirContext = await getDirectoryContextString(this.config);
+    const dirContext = await getDirectoryContextString(this.context.config);
     finalPrompt += `\n\n# Environment Context\n${dirContext}`;
 
     // Append standard rules for non-interactive execution.

packages/core/src/config/agent-loop-context.ts

@@ -7,6 +7,8 @@
 import type { GeminiClient } from '../core/client.js';
 import type { MessageBus } from '../confirmation-bus/message-bus.js';
 import type { ToolRegistry } from '../tools/tool-registry.js';
+import type { PromptRegistry } from '../prompts/prompt-registry.js';
+import type { ResourceRegistry } from '../resources/resource-registry.js';
 import type { SandboxManager } from '../services/sandboxManager.js';
 import type { Config } from './config.js';
 
@@ -24,6 +26,12 @@ export interface AgentLoopContext {
   /** The registry of tools available to the agent in this context. */
   readonly toolRegistry: ToolRegistry;
 
+  /** The registry of prompts available to the agent in this context. */
+  readonly promptRegistry: PromptRegistry;
+
+  /** The registry of resources available to the agent in this context. */
+  readonly resourceRegistry: ResourceRegistry;
+
   /** The bus for user confirmations and messages in this context. */
   readonly messageBus: MessageBus;
 

packages/core/src/config/config.ts

@@ -660,8 +660,8 @@ export class Config implements McpContext, AgentLoopContext {
   private allowedEnvironmentVariables: string[];
   private blockedEnvironmentVariables: string[];
   private readonly enableEnvironmentVariableRedaction: boolean;
-  private promptRegistry!: PromptRegistry;
-  private resourceRegistry!: ResourceRegistry;
+  private _promptRegistry!: PromptRegistry;
+  private _resourceRegistry!: ResourceRegistry;
   private agentRegistry!: AgentRegistry;
   private readonly acknowledgedAgentsService: AcknowledgedAgentsService;
   private skillManager!: SkillManager;
@@ -1245,8 +1245,8 @@ export class Config implements McpContext, AgentLoopContext {
     if (this.getCheckpointingEnabled()) {
       await this.getGitService();
     }
-    this.promptRegistry = new PromptRegistry();
-    this.resourceRegistry = new ResourceRegistry();
+    this._promptRegistry = new PromptRegistry();
+    this._resourceRegistry = new ResourceRegistry();
 
     this.agentRegistry = new AgentRegistry(this);
     await this.agentRegistry.initialize();
@@ -1482,6 +1482,22 @@ export class Config implements McpContext, AgentLoopContext {
     return this._toolRegistry;
   }
 
+  /**
+   * @deprecated Do not access directly on Config.
+   * Use the injected AgentLoopContext instead.
+   */
+  get promptRegistry(): PromptRegistry {
+    return this._promptRegistry;
+  }
+
+  /**
+   * @deprecated Do not access directly on Config.
+   * Use the injected AgentLoopContext instead.
+   */
+  get resourceRegistry(): ResourceRegistry {
+    return this._resourceRegistry;
+  }
+
   /**
    * @deprecated Do not access directly on Config.
    * Use the injected AgentLoopContext instead.
@@ -1794,7 +1810,7 @@ export class Config implements McpContext, AgentLoopContext {
   }
 
   getPromptRegistry(): PromptRegistry {
-    return this.promptRegistry;
+    return this._promptRegistry;
   }
 
   getSkillManager(): SkillManager {
@@ -1802,7 +1818,7 @@ export class Config implements McpContext, AgentLoopContext {
   }
 
   getResourceRegistry(): ResourceRegistry {
-    return this.resourceRegistry;
+    return this._resourceRegistry;
   }
 
   getDebugMode(): boolean {