diff --git a/packages/core/src/agents/agent-scheduler.test.ts b/packages/core/src/agents/agent-scheduler.test.ts
index 451fb276a2..02d780128c 100644
--- a/packages/core/src/agents/agent-scheduler.test.ts
+++ b/packages/core/src/agents/agent-scheduler.test.ts
@@ -19,23 +19,24 @@ vi.mock('../scheduler/scheduler.js', () => ({
 }));
 
 describe('agent-scheduler', () => {
-  let mockConfig: Mocked<Config>;
   let mockToolRegistry: Mocked<ToolRegistry>;
   let mockMessageBus: Mocked<MessageBus>;
 
   beforeEach(() => {
+    vi.mocked(Scheduler).mockClear();
     mockMessageBus = {} as Mocked<MessageBus>;
     mockToolRegistry = {
       getTool: vi.fn(),
       getMessageBus: vi.fn().mockReturnValue(mockMessageBus),
     } as unknown as Mocked<ToolRegistry>;
-    mockConfig = {
-      getMessageBus: vi.fn().mockReturnValue(mockMessageBus),
-      toolRegistry: mockToolRegistry,
-    } as unknown as Mocked<Config>;
   });
 
   it('should create a scheduler with agent-specific config', async () => {
+    const mockConfig = {
+      getMessageBus: vi.fn().mockReturnValue(mockMessageBus),
+      toolRegistry: mockToolRegistry,
+    } as unknown as Mocked<Config>;
+
     const requests: ToolCallRequestInfo[] = [
       {
         callId: 'call-1',
@@ -68,8 +69,46 @@ describe('agent-scheduler', () => {
       }),
     );
 
-    // Verify that the scheduler's config has the overridden tool registry
     const schedulerConfig = vi.mocked(Scheduler).mock.calls[0][0].config;
     expect(schedulerConfig.toolRegistry).toBe(mockToolRegistry);
   });
+
+  it('should override toolRegistry getter from prototype chain', async () => {
+    const mainRegistry = { _id: 'main' } as unknown as Mocked<ToolRegistry>;
+    const agentRegistry = {
+      _id: 'agent',
+      getMessageBus: vi.fn().mockReturnValue(mockMessageBus),
+    } as unknown as Mocked<ToolRegistry>;
+
+    const config = {
+      getMessageBus: vi.fn().mockReturnValue(mockMessageBus),
+    } as unknown as Mocked<Config>;
+    Object.defineProperty(config, 'toolRegistry', {
+      get: () => mainRegistry,
+      configurable: true,
+    });
+
+    await scheduleAgentTools(
+      config as unknown as Config,
+      [
+        {
+          callId: 'c1',
+          name: 'new_page',
+          args: {},
+          isClientInitiated: false,
+          prompt_id: 'p1',
+        },
+      ],
+      {
+        schedulerId: 'browser-1',
+        toolRegistry: agentRegistry as unknown as ToolRegistry,
+        signal: new AbortController().signal,
+      },
+    );
+
+    const schedulerConfig = vi.mocked(Scheduler).mock.calls[0][0].config;
+    expect(schedulerConfig.toolRegistry).toBe(agentRegistry);
+    expect(schedulerConfig.toolRegistry).not.toBe(mainRegistry);
+    expect(schedulerConfig.getToolRegistry()).toBe(agentRegistry);
+  });
 });
diff --git a/packages/core/src/agents/agent-scheduler.ts b/packages/core/src/agents/agent-scheduler.ts
index 983f814b0f..3b78ec47ee 100644
--- a/packages/core/src/agents/agent-scheduler.ts
+++ b/packages/core/src/agents/agent-scheduler.ts
@@ -58,6 +58,11 @@ export async function scheduleAgentTools(
   const agentConfig: Config = Object.create(config);
   agentConfig.getToolRegistry = () => toolRegistry;
   agentConfig.getMessageBus = () => toolRegistry.getMessageBus();
+  // Override toolRegistry property so AgentLoopContext reads the agent-specific registry.
+  Object.defineProperty(agentConfig, 'toolRegistry', {
+    get: () => toolRegistry,
+    configurable: true,
+  });
 
   const scheduler = new Scheduler({
     config: agentConfig,
diff --git a/packages/core/src/agents/browser/browserAgentFactory.test.ts b/packages/core/src/agents/browser/browserAgentFactory.test.ts
index a317f3a9ed..96fba50d4f 100644
--- a/packages/core/src/agents/browser/browserAgentFactory.test.ts
+++ b/packages/core/src/agents/browser/browserAgentFactory.test.ts
@@ -209,6 +209,45 @@ describe('browserAgentFactory', () => {
           .map((t) => t.name) ?? [];
       expect(toolNames).toContain('analyze_screenshot');
     });
+
+    it('should include all MCP navigation tools (new_page, navigate_page) in definition', async () => {
+      mockBrowserManager.getDiscoveredTools.mockResolvedValue([
+        { name: 'take_snapshot', description: 'Take snapshot' },
+        { name: 'click', description: 'Click element' },
+        { name: 'fill', description: 'Fill form field' },
+        { name: 'navigate_page', description: 'Navigate to URL' },
+        { name: 'new_page', description: 'Open a new page/tab' },
+        { name: 'close_page', description: 'Close page' },
+        { name: 'select_page', description: 'Select page' },
+        { name: 'press_key', description: 'Press key' },
+        { name: 'hover', description: 'Hover element' },
+      ]);
+
+      const { definition } = await createBrowserAgentDefinition(
+        mockConfig,
+        mockMessageBus,
+      );
+
+      const toolNames =
+        definition.toolConfig?.tools
+          ?.filter(
+            (t): t is { name: string } => typeof t === 'object' && 'name' in t,
+          )
+          .map((t) => t.name) ?? [];
+
+      // All MCP tools must be present
+      expect(toolNames).toContain('new_page');
+      expect(toolNames).toContain('navigate_page');
+      expect(toolNames).toContain('close_page');
+      expect(toolNames).toContain('select_page');
+      expect(toolNames).toContain('click');
+      expect(toolNames).toContain('take_snapshot');
+      expect(toolNames).toContain('press_key');
+      // Custom composite tool must also be present
+      expect(toolNames).toContain('type_text');
+      // Total: 9 MCP + 1 type_text (no analyze_screenshot without visualModel)
+      expect(definition.toolConfig?.tools).toHaveLength(10);
+    });
   });
 
   describe('cleanupBrowserAgent', () => {