feat(core,cli): enforce mandatory MessageBus injection (Phase 3 Hard Migration) (#15776)

packages/core/src/tools/activate-skill.test.ts

@@ -8,6 +8,7 @@ import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { ActivateSkillTool } from './activate-skill.js';
 import type { Config } from '../config/config.js';
 import type { MessageBus } from '../confirmation-bus/message-bus.js';
+import { createMockMessageBus } from '../test-utils/mock-message-bus.js';
 
 vi.mock('../utils/getFolderStructure.js', () => ({
   getFolderStructure: vi.fn().mockResolvedValue('Mock folder structure'),
@@ -16,13 +17,10 @@ vi.mock('../utils/getFolderStructure.js', () => ({
 describe('ActivateSkillTool', () => {
   let mockConfig: Config;
   let tool: ActivateSkillTool;
-  const mockMessageBus = {
-    publish: vi.fn(),
-    subscribe: vi.fn(),
-    unsubscribe: vi.fn(),
-  } as unknown as MessageBus;
+  let mockMessageBus: MessageBus;
 
   beforeEach(() => {
+    mockMessageBus = createMockMessageBus();
     const skills = [
       {
         name: 'test-skill',

packages/core/src/tools/activate-skill.ts

@@ -38,7 +38,7 @@ class ActivateSkillToolInvocation extends BaseToolInvocation<
   constructor(
     private config: Config,
     params: ActivateSkillToolParams,
-    messageBus: MessageBus | undefined,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -145,7 +145,7 @@ export class ActivateSkillTool extends BaseDeclarativeTool<
 
   constructor(
     private config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     const skills = config.getSkillManager().getSkills();
     const skillNames = skills.map((s) => s.name);
@@ -169,15 +169,15 @@ export class ActivateSkillTool extends BaseDeclarativeTool<
       "Activates a specialized agent skill by name. Returns the skill's instructions wrapped in `<ACTIVATED_SKILL>` tags. These provide specialized guidance for the current task. Use this when you identify a task that matches a skill's description.",
       Kind.Other,
       zodToJsonSchema(schema),
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
   protected createInvocation(
     params: ActivateSkillToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<ActivateSkillToolParams, ToolResult> {

packages/core/src/tools/edit.ts

@@ -118,7 +118,7 @@ class EditToolInvocation
   constructor(
     private readonly config: Config,
     params: EditToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     toolName?: string,
     displayName?: string,
   ) {
@@ -492,7 +492,7 @@ export class EditTool
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       EditTool.Name,
@@ -535,9 +535,9 @@ Expectation for required parameters:
         required: ['file_path', 'old_string', 'new_string'],
         type: 'object',
       },
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
   }
 
@@ -568,14 +568,14 @@ Expectation for required parameters:
 
   protected createInvocation(
     params: EditToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     toolName?: string,
     displayName?: string,
   ): ToolInvocation<EditToolParams, ToolResult> {
     return new EditToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       toolName ?? this.name,
       displayName ?? this.displayName,
     );

packages/core/src/tools/get-internal-docs.test.ts

@@ -9,13 +9,14 @@ import { GetInternalDocsTool } from './get-internal-docs.js';
 import { ToolErrorType } from './tool-error.js';
 import fs from 'node:fs/promises';
 import path from 'node:path';
+import { createMockMessageBus } from '../test-utils/mock-message-bus.js';
 
 describe('GetInternalDocsTool (Integration)', () => {
   let tool: GetInternalDocsTool;
   const abortSignal = new AbortController().signal;
 
   beforeEach(() => {
-    tool = new GetInternalDocsTool();
+    tool = new GetInternalDocsTool(createMockMessageBus());
   });
 
   it('should find the documentation root and list files', async () => {

packages/core/src/tools/get-internal-docs.ts

@@ -82,7 +82,7 @@ class GetInternalDocsInvocation extends BaseToolInvocation<
 > {
   constructor(
     params: GetInternalDocsParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -161,7 +161,7 @@ export class GetInternalDocsTool extends BaseDeclarativeTool<
 > {
   static readonly Name = GET_INTERNAL_DOCS_TOOL_NAME;
 
-  constructor(messageBus?: MessageBus) {
+  constructor(messageBus: MessageBus) {
     super(
       GetInternalDocsTool.Name,
       'GetInternalDocs',
@@ -177,21 +177,21 @@ export class GetInternalDocsTool extends BaseDeclarativeTool<
           },
         },
       },
+      messageBus,
       /* isOutputMarkdown */ true,
       /* canUpdateOutput */ false,
-      messageBus,
     );
   }
 
   protected createInvocation(
     params: GetInternalDocsParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<GetInternalDocsParams, ToolResult> {
     return new GetInternalDocsInvocation(
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName ?? GetInternalDocsTool.Name,
       _toolDisplayName,
     );

packages/core/src/tools/glob.ts

@@ -91,7 +91,7 @@ class GlobToolInvocation extends BaseToolInvocation<
   constructor(
     private config: Config,
     params: GlobToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -262,7 +262,7 @@ export class GlobTool extends BaseDeclarativeTool<GlobToolParams, ToolResult> {
   static readonly Name = GLOB_TOOL_NAME;
   constructor(
     private config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       GlobTool.Name,
@@ -300,9 +300,9 @@ export class GlobTool extends BaseDeclarativeTool<GlobToolParams, ToolResult> {
         required: ['pattern'],
         type: 'object',
       },
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
@@ -348,14 +348,14 @@ export class GlobTool extends BaseDeclarativeTool<GlobToolParams, ToolResult> {
 
   protected createInvocation(
     params: GlobToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<GlobToolParams, ToolResult> {
     return new GlobToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/grep.ts

@@ -62,7 +62,7 @@ class GrepToolInvocation extends BaseToolInvocation<
   constructor(
     private readonly config: Config,
     params: GrepToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -571,7 +571,7 @@ export class GrepTool extends BaseDeclarativeTool<GrepToolParams, ToolResult> {
   static readonly Name = GREP_TOOL_NAME;
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       GrepTool.Name,
@@ -599,9 +599,9 @@ export class GrepTool extends BaseDeclarativeTool<GrepToolParams, ToolResult> {
         required: ['pattern'],
         type: 'object',
       },
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
@@ -674,14 +674,14 @@ export class GrepTool extends BaseDeclarativeTool<GrepToolParams, ToolResult> {
 
   protected createInvocation(
     params: GrepToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<GrepToolParams, ToolResult> {
     return new GrepToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/ls.ts

@@ -73,7 +73,7 @@ class LSToolInvocation extends BaseToolInvocation<LSToolParams, ToolResult> {
   constructor(
     private readonly config: Config,
     params: LSToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -259,7 +259,7 @@ export class LSTool extends BaseDeclarativeTool<LSToolParams, ToolResult> {
 
   constructor(
     private config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       LSTool.Name,
@@ -300,9 +300,9 @@ export class LSTool extends BaseDeclarativeTool<LSToolParams, ToolResult> {
         required: ['dir_path'],
         type: 'object',
       },
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
@@ -330,7 +330,7 @@ export class LSTool extends BaseDeclarativeTool<LSToolParams, ToolResult> {
 
   protected createInvocation(
     params: LSToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<LSToolParams, ToolResult> {

packages/core/src/tools/mcp-client.ts

@@ -57,7 +57,7 @@ import type {
 } from '../utils/workspaceContext.js';
 import type { ToolRegistry } from './tool-registry.js';
 import { debugLogger } from '../utils/debugLogger.js';
-import type { MessageBus } from '../confirmation-bus/message-bus.js';
+import { type MessageBus } from '../confirmation-bus/message-bus.js';
 import { coreEvents } from '../utils/events.js';
 import type { ResourceRegistry } from '../resources/resource-registry.js';
 import {
@@ -895,7 +895,7 @@ export async function discoverTools(
   mcpServerConfig: MCPServerConfig,
   mcpClient: Client,
   cliConfig: Config,
-  messageBus?: MessageBus,
+  messageBus: MessageBus,
   options?: { timeout?: number; signal?: AbortSignal },
 ): Promise<DiscoveredMCPTool[]> {
   try {
@@ -922,12 +922,12 @@ export async function discoverTools(
           toolDef.name,
           toolDef.description ?? '',
           toolDef.inputSchema ?? { type: 'object', properties: {} },
+          messageBus,
           mcpServerConfig.trust,
           undefined,
           cliConfig,
           mcpServerConfig.extension?.name,
           mcpServerConfig.extension?.id,
-          messageBus,
         );
 
         discoveredTools.push(tool);

packages/core/src/tools/mcp-tool.test.ts

@@ -13,6 +13,10 @@ import type { ToolResult } from './tools.js';
 import { ToolConfirmationOutcome } from './tools.js'; // Added ToolConfirmationOutcome
 import type { CallableTool, Part } from '@google/genai';
 import { ToolErrorType } from './tool-error.js';
+import {
+  createMockMessageBus,
+  getMockMessageBusInstance,
+} from '../test-utils/mock-message-bus.js';
 
 // Mock @google/genai mcpToTool and CallableTool
 // We only need to mock the parts of CallableTool that DiscoveredMCPTool uses.
@@ -85,12 +89,15 @@ describe('DiscoveredMCPTool', () => {
   beforeEach(() => {
     mockCallTool.mockClear();
     mockToolMethod.mockClear();
+    const bus = createMockMessageBus();
+    getMockMessageBusInstance(bus).defaultToolDecision = 'ask_user';
     tool = new DiscoveredMCPTool(
       mockCallableToolInstance,
       serverName,
       serverToolName,
       baseDescription,
       inputSchema,
+      bus,
     );
     // Clear allowlist before each relevant test, especially for shouldConfirmExecute
     const invocation = tool.build({ param: 'mock' }) as any;
@@ -190,6 +197,12 @@ describe('DiscoveredMCPTool', () => {
           serverToolName,
           baseDescription,
           inputSchema,
+          createMockMessageBus(),
+          undefined,
+          undefined,
+          undefined,
+          undefined,
+          undefined,
         );
         const params = { param: 'isErrorTrueCase' };
         const functionCall = {
@@ -230,6 +243,12 @@ describe('DiscoveredMCPTool', () => {
         serverToolName,
         baseDescription,
         inputSchema,
+        createMockMessageBus(),
+        undefined,
+        undefined,
+        undefined,
+        undefined,
+        undefined,
       );
       const params = { param: 'isErrorTopLevelCase' };
       const functionCall = {
@@ -273,6 +292,12 @@ describe('DiscoveredMCPTool', () => {
           serverToolName,
           baseDescription,
           inputSchema,
+          createMockMessageBus(),
+          undefined,
+          undefined,
+          undefined,
+          undefined,
+          undefined,
         );
         const params = { param: 'isErrorFalseCase' };
         const mockToolSuccessResultObject = {
@@ -728,9 +753,12 @@ describe('DiscoveredMCPTool', () => {
         serverToolName,
         baseDescription,
         inputSchema,
+        createMockMessageBus(),
         true,
         undefined,
         { isTrustedFolder: () => true } as any,
+        undefined,
+        undefined,
       );
       const invocation = trustedTool.build({ param: 'mock' });
       expect(
@@ -862,15 +890,20 @@ describe('DiscoveredMCPTool', () => {
           'return confirmation details if trust is false, even if folder is trusted',
       },
     ])('should $description', async ({ trust, isTrusted, shouldConfirm }) => {
+      const bus = createMockMessageBus();
+      getMockMessageBusInstance(bus).defaultToolDecision = 'ask_user';
       const testTool = new DiscoveredMCPTool(
         mockCallableToolInstance,
         serverName,
         serverToolName,
         baseDescription,
         inputSchema,
+        bus,
         trust,
         undefined,
         mockConfig(isTrusted) as any,
+        undefined,
+        undefined,
       );
       const invocation = testTool.build({ param: 'mock' });
       const confirmation = await invocation.shouldConfirmExecute(

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

@@ -70,10 +70,10 @@ class DiscoveredMCPToolInvocation extends BaseToolInvocation<
     readonly serverName: string,
     readonly serverToolName: string,
     readonly displayName: string,
+    messageBus: MessageBus,
     readonly trust?: boolean,
     params: ToolParams = {},
     private readonly cliConfig?: Config,
-    messageBus?: MessageBus,
   ) {
     // Use composite format for policy checks: serverName__toolName
     // This enables server wildcards (e.g., "google-workspace__*")
@@ -239,12 +239,12 @@ export class DiscoveredMCPTool extends BaseDeclarativeTool<
     readonly serverToolName: string,
     description: string,
     override readonly parameterSchema: unknown,
+    messageBus: MessageBus,
     readonly trust?: boolean,
     nameOverride?: string,
     private readonly cliConfig?: Config,
     override readonly extensionName?: string,
     override readonly extensionId?: string,
-    messageBus?: MessageBus,
   ) {
     super(
       nameOverride ?? generateValidName(serverToolName),
@@ -252,9 +252,9 @@ export class DiscoveredMCPTool extends BaseDeclarativeTool<
       description,
       Kind.Other,
       parameterSchema,
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput,
-      messageBus,
       extensionName,
       extensionId,
     );
@@ -271,18 +271,18 @@ export class DiscoveredMCPTool extends BaseDeclarativeTool<
       this.serverToolName,
       this.description,
       this.parameterSchema,
+      this.messageBus,
       this.trust,
       `${this.getFullyQualifiedPrefix()}${this.serverToolName}`,
       this.cliConfig,
       this.extensionName,
       this.extensionId,
-      this.messageBus,
     );
   }
 
   protected createInvocation(
     params: ToolParams,
-    _messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _displayName?: string,
   ): ToolInvocation<ToolParams, ToolResult> {
@@ -291,10 +291,10 @@ export class DiscoveredMCPTool extends BaseDeclarativeTool<
       this.serverName,
       this.serverToolName,
       _displayName ?? this.displayName,
+      messageBus,
       this.trust,
       params,
       this.cliConfig,
-      _messageBus ?? this.messageBus,
     );
   }
 }

packages/core/src/tools/memoryTool.test.ts

@@ -19,6 +19,10 @@ import * as os from 'node:os';
 import { ToolConfirmationOutcome } from './tools.js';
 import { ToolErrorType } from './tool-error.js';
 import { GEMINI_DIR } from '../utils/paths.js';
+import {
+  createMockMessageBus,
+  getMockMessageBusInstance,
+} from '../test-utils/mock-message-bus.js';
 
 // Mock dependencies
 vi.mock(import('node:fs/promises'), async (importOriginal) => {
@@ -200,7 +204,7 @@ describe('MemoryTool', () => {
     let performAddMemoryEntrySpy: Mock<typeof MemoryTool.performAddMemoryEntry>;
 
     beforeEach(() => {
-      memoryTool = new MemoryTool();
+      memoryTool = new MemoryTool(createMockMessageBus());
       // Spy on the static method for these tests
       performAddMemoryEntrySpy = vi
         .spyOn(MemoryTool, 'performAddMemoryEntry')
@@ -300,7 +304,9 @@ describe('MemoryTool', () => {
     let memoryTool: MemoryTool;
 
     beforeEach(() => {
-      memoryTool = new MemoryTool();
+      const bus = createMockMessageBus();
+      getMockMessageBusInstance(bus).defaultToolDecision = 'ask_user';
+      memoryTool = new MemoryTool(bus);
       // Clear the allowlist before each test
       const invocation = memoryTool.build({ fact: 'mock-fact' });
       // eslint-disable-next-line @typescript-eslint/no-explicit-any

packages/core/src/tools/memoryTool.ts

@@ -179,7 +179,7 @@ class MemoryToolInvocation extends BaseToolInvocation<
 
   constructor(
     params: SaveMemoryParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     toolName?: string,
     displayName?: string,
   ) {
@@ -298,16 +298,16 @@ export class MemoryTool
 {
   static readonly Name = MEMORY_TOOL_NAME;
 
-  constructor(messageBus?: MessageBus) {
+  constructor(messageBus: MessageBus) {
     super(
       MemoryTool.Name,
       'SaveMemory',
       memoryToolDescription,
       Kind.Think,
       memoryToolSchemaData.parametersJsonSchema as Record<string, unknown>,
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
@@ -323,13 +323,13 @@ export class MemoryTool
 
   protected createInvocation(
     params: SaveMemoryParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     toolName?: string,
     displayName?: string,
   ) {
     return new MemoryToolInvocation(
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       toolName ?? this.name,
       displayName ?? this.displayName,
     );

packages/core/src/tools/message-bus-integration.test.ts

@@ -81,21 +81,21 @@ class TestTool extends BaseDeclarativeTool<TestParams, TestResult> {
         },
         required: ['testParam'],
       },
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
   protected createInvocation(
     params: TestParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
     return new TestToolInvocation(
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/read-file.ts

@@ -50,7 +50,7 @@ class ReadFileToolInvocation extends BaseToolInvocation<
   constructor(
     private config: Config,
     params: ReadFileToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -149,7 +149,7 @@ export class ReadFileTool extends BaseDeclarativeTool<
 
   constructor(
     private config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       ReadFileTool.Name,
@@ -176,9 +176,9 @@ export class ReadFileTool extends BaseDeclarativeTool<
         required: ['file_path'],
         type: 'object',
       },
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
@@ -225,14 +225,14 @@ export class ReadFileTool extends BaseDeclarativeTool<
 
   protected createInvocation(
     params: ReadFileToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<ReadFileToolParams, ToolResult> {
     return new ReadFileToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/read-many-files.ts

@@ -107,7 +107,7 @@ class ReadManyFilesToolInvocation extends BaseToolInvocation<
   constructor(
     private readonly config: Config,
     params: ReadManyFilesParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -447,7 +447,7 @@ export class ReadManyFilesTool extends BaseDeclarativeTool<
 
   constructor(
     private config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     const parameterSchema = {
       type: 'object',
@@ -520,22 +520,22 @@ This tool is useful when you need to understand or analyze a collection of files
 Use this tool when the user's query implies needing the content of several files simultaneously for context, analysis, or summarization. For text files, it uses default UTF-8 encoding and a '--- {filePath} ---' separator between file contents. The tool inserts a '--- End of content ---' after the last file. Ensure glob patterns are relative to the target directory. Glob patterns like 'src/**/*.js' are supported. Avoid using for single files if a more specific single-file reading tool is available, unless the user specifically requests to process a list containing just one file via this tool. Other binary files (not explicitly requested as image/audio/PDF) are generally skipped. Default excludes apply to common non-text files (except for explicitly requested images/audio/PDFs) and large dependency directories unless 'useDefaultExcludes' is false.`,
       Kind.Read,
       parameterSchema,
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
   }
 
   protected createInvocation(
     params: ReadManyFilesParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<ReadManyFilesParams, ToolResult> {
     return new ReadManyFilesToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/ripGrep.test.ts

@@ -24,6 +24,7 @@ import { createMockWorkspaceContext } from '../test-utils/mockWorkspaceContext.j
 import type { ChildProcess } from 'node:child_process';
 import { spawn } from 'node:child_process';
 import { downloadRipGrep } from '@joshua.litt/get-ripgrep';
+import { createMockMessageBus } from '../test-utils/mock-message-bus.js';
 // Mock dependencies for canUseRipgrep
 vi.mock('@joshua.litt/get-ripgrep', () => ({
   downloadRipGrep: vi.fn(),
@@ -267,7 +268,7 @@ describe('RipGrepTool', () => {
     await fs.writeFile(ripgrepBinaryPath, '');
     storageSpy.mockImplementation(() => binDir);
     tempRootDir = await fs.mkdtemp(path.join(os.tmpdir(), 'grep-tool-root-'));
-    grepTool = new RipGrepTool(mockConfig);
+    grepTool = new RipGrepTool(mockConfig, createMockMessageBus());
 
     // Create some test files and directories
     await fs.writeFile(
@@ -833,7 +834,10 @@ describe('RipGrepTool', () => {
         return mockProcess as unknown as ChildProcess;
       });
 
-      const multiDirGrepTool = new RipGrepTool(multiDirConfig);
+      const multiDirGrepTool = new RipGrepTool(
+        multiDirConfig,
+        createMockMessageBus(),
+      );
       const params: RipGrepToolParams = { pattern: 'world' };
       const invocation = multiDirGrepTool.build(params);
       const result = await invocation.execute(abortSignal);
@@ -927,7 +931,10 @@ describe('RipGrepTool', () => {
         return mockProcess as unknown as ChildProcess;
       });
 
-      const multiDirGrepTool = new RipGrepTool(multiDirConfig);
+      const multiDirGrepTool = new RipGrepTool(
+        multiDirConfig,
+        createMockMessageBus(),
+      );
 
       // Search only in the 'sub' directory of the first workspace
       const params: RipGrepToolParams = { pattern: 'world', dir_path: 'sub' };
@@ -1656,7 +1663,10 @@ describe('RipGrepTool', () => {
         getDebugMode: () => false,
         getFileFilteringRespectGeminiIgnore: () => true,
       } as unknown as Config;
-      const geminiIgnoreTool = new RipGrepTool(configWithGeminiIgnore);
+      const geminiIgnoreTool = new RipGrepTool(
+        configWithGeminiIgnore,
+        createMockMessageBus(),
+      );
 
       mockSpawn.mockImplementationOnce(
         createMockSpawn({
@@ -1693,7 +1703,10 @@ describe('RipGrepTool', () => {
         getDebugMode: () => false,
         getFileFilteringRespectGeminiIgnore: () => false,
       } as unknown as Config;
-      const geminiIgnoreTool = new RipGrepTool(configWithoutGeminiIgnore);
+      const geminiIgnoreTool = new RipGrepTool(
+        configWithoutGeminiIgnore,
+        createMockMessageBus(),
+      );
 
       mockSpawn.mockImplementationOnce(
         createMockSpawn({
@@ -1816,7 +1829,10 @@ describe('RipGrepTool', () => {
         getDebugMode: () => false,
       } as unknown as Config;
 
-      const multiDirGrepTool = new RipGrepTool(multiDirConfig);
+      const multiDirGrepTool = new RipGrepTool(
+        multiDirConfig,
+        createMockMessageBus(),
+      );
       const params: RipGrepToolParams = { pattern: 'testPattern' };
       const invocation = multiDirGrepTool.build(params);
       expect(invocation.getDescription()).toBe("'testPattern' within ./");

packages/core/src/tools/ripGrep.ts

@@ -192,7 +192,7 @@ class GrepToolInvocation extends BaseToolInvocation<
     private readonly config: Config,
     private readonly geminiIgnoreParser: GeminiIgnoreParser,
     params: RipGrepToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -493,7 +493,7 @@ export class RipGrepTool extends BaseDeclarativeTool<
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       RipGrepTool.Name,
@@ -551,9 +551,9 @@ export class RipGrepTool extends BaseDeclarativeTool<
         required: ['pattern'],
         type: 'object',
       },
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
     this.geminiIgnoreParser = new GeminiIgnoreParser(config.getTargetDir());
   }
@@ -586,7 +586,7 @@ export class RipGrepTool extends BaseDeclarativeTool<
 
   protected createInvocation(
     params: RipGrepToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<RipGrepToolParams, ToolResult> {

packages/core/src/tools/shell.ts

@@ -57,7 +57,7 @@ export class ShellToolInvocation extends BaseToolInvocation<
   constructor(
     private readonly config: Config,
     params: ShellToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -420,7 +420,7 @@ export class ShellTool extends BaseDeclarativeTool<
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     void initializeShellParsers().catch(() => {
       // Errors are surfaced when parsing commands.
@@ -450,9 +450,9 @@ export class ShellTool extends BaseDeclarativeTool<
         },
         required: ['command'],
       },
+      messageBus,
       false, // output is not markdown
       true, // output can be updated
-      messageBus,
     );
   }
 
@@ -478,14 +478,14 @@ export class ShellTool extends BaseDeclarativeTool<
 
   protected createInvocation(
     params: ShellToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<ShellToolParams, ToolResult> {
     return new ShellToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/smart-edit.test.ts

@@ -49,6 +49,10 @@ import {
 } from './smart-edit.js';
 import { type FileDiff, ToolConfirmationOutcome } from './tools.js';
 import { ToolErrorType } from './tool-error.js';
+import {
+  createMockMessageBus,
+  getMockMessageBusInstance,
+} from '../test-utils/mock-message-bus.js';
 import path from 'node:path';
 import fs from 'node:fs';
 import os from 'node:os';
@@ -165,7 +169,9 @@ describe('SmartEditTool', () => {
       },
     );
 
-    tool = new SmartEditTool(mockConfig);
+    const bus = createMockMessageBus();
+    getMockMessageBusInstance(bus).defaultToolDecision = 'ask_user';
+    tool = new SmartEditTool(mockConfig, bus);
   });
 
   afterEach(() => {

packages/core/src/tools/smart-edit.ts

@@ -386,7 +386,7 @@ class EditToolInvocation
   constructor(
     private readonly config: Config,
     params: EditToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     toolName?: string,
     displayName?: string,
   ) {
@@ -853,7 +853,7 @@ export class SmartEditTool
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       SmartEditTool.Name,
@@ -915,9 +915,9 @@ A good instruction should concisely answer:
         required: ['file_path', 'instruction', 'old_string', 'new_string'],
         type: 'object',
       },
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
   }
 
@@ -955,12 +955,12 @@ A good instruction should concisely answer:
 
   protected createInvocation(
     params: EditToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ): ToolInvocation<EditToolParams, ToolResult> {
     return new EditToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       this.name,
       this.displayName,
     );

packages/core/src/tools/tool-registry.test.ts

@@ -90,12 +90,26 @@ const createMockCallableTool = (
 });
 
 // Helper to create a DiscoveredMCPTool
+const mockMessageBusForHelper = {
+  publish: vi.fn(),
+  subscribe: vi.fn(),
+  unsubscribe: vi.fn(),
+} as unknown as MessageBus;
+
 const createMCPTool = (
   serverName: string,
   toolName: string,
   description: string,
   mockCallable: CallableTool = {} as CallableTool,
-) => new DiscoveredMCPTool(mockCallable, serverName, toolName, description, {});
+) =>
+  new DiscoveredMCPTool(
+    mockCallable,
+    serverName,
+    toolName,
+    description,
+    {},
+    mockMessageBusForHelper,
+  );
 
 // Helper to create a mock spawn process for tool discovery
 const createDiscoveryProcess = (toolDeclarations: FunctionDeclaration[]) => {
@@ -171,6 +185,11 @@ const baseConfigParams: ConfigParameters = {
 describe('ToolRegistry', () => {
   let config: Config;
   let toolRegistry: ToolRegistry;
+  const mockMessageBus = {
+    publish: vi.fn(),
+    subscribe: vi.fn(),
+    unsubscribe: vi.fn(),
+  } as unknown as MessageBus;
   let mockConfigGetToolDiscoveryCommand: ReturnType<typeof vi.spyOn>;
   let mockConfigGetExcludedTools: MockInstance<
     typeof Config.prototype.getExcludeTools
@@ -182,7 +201,7 @@ describe('ToolRegistry', () => {
       isDirectory: () => true,
     } as fs.Stats);
     config = new Config(baseConfigParams);
-    toolRegistry = new ToolRegistry(config);
+    toolRegistry = new ToolRegistry(config, mockMessageBus);
     vi.spyOn(console, 'warn').mockImplementation(() => {});
     vi.spyOn(console, 'error').mockImplementation(() => {});
     vi.spyOn(console, 'debug').mockImplementation(() => {});
@@ -372,6 +391,7 @@ describe('ToolRegistry', () => {
         DISCOVERED_TOOL_PREFIX + 'discovered-1',
         'desc',
         {},
+        mockMessageBus,
       );
       const mcpZebra = createMCPTool('zebra-server', 'mcp-zebra', 'desc');
       const mcpApple = createMCPTool('apple-server', 'mcp-apple', 'desc');
@@ -482,13 +502,6 @@ describe('ToolRegistry', () => {
       const discoveryCommand = 'my-discovery-command';
       mockConfigGetToolDiscoveryCommand.mockReturnValue(discoveryCommand);
 
-      const mockMessageBus = {
-        publish: vi.fn(),
-        subscribe: vi.fn(),
-        unsubscribe: vi.fn(),
-      } as unknown as MessageBus;
-      toolRegistry.setMessageBus(mockMessageBus);
-
       const toolDeclaration: FunctionDeclaration = {
         name: 'policy-test-tool',
         description: 'tests policy',
@@ -520,6 +533,7 @@ describe('ToolRegistry', () => {
         DISCOVERED_TOOL_PREFIX + 'test-tool',
         'A test tool',
         {},
+        mockMessageBus,
       );
       const params = { param: 'testValue' };
       const invocation = tool.build(params);

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

@@ -34,7 +34,7 @@ class DiscoveredToolInvocation extends BaseToolInvocation<
     private readonly originalToolName: string,
     prefixedToolName: string,
     params: ToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(params, messageBus, prefixedToolName);
   }
@@ -135,7 +135,7 @@ export class DiscoveredTool extends BaseDeclarativeTool<
     prefixedName: string,
     description: string,
     override readonly parameterSchema: Record<string, unknown>,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     const discoveryCmd = config.getToolDiscoveryCommand()!;
     const callCommand = config.getToolCallCommand()!;
@@ -163,16 +163,16 @@ Signal: Signal number or \`(none)\` if no signal was received.
       fullDescription,
       Kind.Other,
       parameterSchema,
+      messageBus,
       false, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
     this.originalName = originalName;
   }
 
   protected createInvocation(
     params: ToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _displayName?: string,
   ): ToolInvocation<ToolParams, ToolResult> {
@@ -181,7 +181,7 @@ Signal: Signal number or \`(none)\` if no signal was received.
       this.originalName,
       _toolName ?? this.name,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
     );
   }
 }
@@ -192,26 +192,17 @@ export class ToolRegistry {
   // and `isActive` to get only the active tools.
   private allKnownTools: Map<string, AnyDeclarativeTool> = new Map();
   private config: Config;
-  private messageBus?: MessageBus;
+  private messageBus: MessageBus;
 
-  constructor(config: Config, messageBus?: MessageBus) {
+  constructor(config: Config, messageBus: MessageBus) {
     this.config = config;
     this.messageBus = messageBus;
   }
 
-  getMessageBus(): MessageBus | undefined {
+  getMessageBus(): MessageBus {
     return this.messageBus;
   }
 
-  /**
-   * @deprecated migration only - will be removed in PR 3 (Enforcement)
-   * TODO: DELETE ME in PR 3. This is a temporary shim to allow for soft migration
-   * of tools while the core infrastructure is updated to require a MessageBus at birth.
-   */
-  setMessageBus(messageBus: MessageBus): void {
-    this.messageBus = messageBus;
-  }
-
   /**
    * Registers a tool definition.
    *

packages/core/src/tools/tools.test.ts

@@ -8,6 +8,7 @@ import { describe, it, expect, vi } from 'vitest';
 import type { ToolInvocation, ToolResult } from './tools.js';
 import { DeclarativeTool, hasCycleInSchema, Kind } from './tools.js';
 import { ToolErrorType } from './tool-error.js';
+import { createMockMessageBus } from '../test-utils/mock-message-bus.js';
 
 class TestToolInvocation implements ToolInvocation<object, ToolResult> {
   constructor(
@@ -36,7 +37,16 @@ class TestTool extends DeclarativeTool<object, ToolResult> {
   private readonly buildFn: (params: object) => TestToolInvocation;
 
   constructor(buildFn: (params: object) => TestToolInvocation) {
-    super('test-tool', 'Test Tool', 'A tool for testing', Kind.Other, {});
+    super(
+      'test-tool',
+      'Test Tool',
+      'A tool for testing',
+      Kind.Other,
+      {},
+      createMockMessageBus(),
+      true, // isOutputMarkdown
+      false, // canUpdateOutput
+    );
     this.buildFn = buildFn;
   }
 

packages/core/src/tools/tools.ts

@@ -83,7 +83,7 @@ export abstract class BaseToolInvocation<
 {
   constructor(
     readonly params: TParams,
-    protected readonly messageBus?: MessageBus,
+    protected readonly messageBus: MessageBus,
     readonly _toolName?: string,
     readonly _toolDisplayName?: string,
     readonly _serverName?: string,
@@ -98,25 +98,24 @@ export abstract class BaseToolInvocation<
   async shouldConfirmExecute(
     abortSignal: AbortSignal,
   ): Promise<ToolCallConfirmationDetails | false> {
-    if (this.messageBus) {
-      const decision = await this.getMessageBusDecision(abortSignal);
-      if (decision === 'ALLOW') {
-        return false;
-      }
-
-      if (decision === 'DENY') {
-        throw new Error(
-          `Tool execution for "${
-            this._toolDisplayName || this._toolName
-          }" denied by policy.`,
-        );
-      }
-
-      if (decision === 'ASK_USER') {
-        return this.getConfirmationDetails(abortSignal);
-      }
+    const decision = await this.getMessageBusDecision(abortSignal);
+    if (decision === 'ALLOW') {
+      return false;
     }
-    // When no message bus, use default confirmation flow
+
+    if (decision === 'DENY') {
+      throw new Error(
+        `Tool execution for "${
+          this._toolDisplayName || this._toolName
+        }" denied by policy.`,
+      );
+    }
+
+    if (decision === 'ASK_USER') {
+      return this.getConfirmationDetails(abortSignal);
+    }
+
+    // Default to confirmation details if decision is unknown (should not happen with exhaustive policy)
     return this.getConfirmationDetails(abortSignal);
   }
 
@@ -142,7 +141,7 @@ export abstract class BaseToolInvocation<
       outcome === ToolConfirmationOutcome.ProceedAlways ||
       outcome === ToolConfirmationOutcome.ProceedAlwaysAndSave
     ) {
-      if (this.messageBus && this._toolName) {
+      if (this._toolName) {
         const options = this.getPolicyUpdateOptions(outcome);
         await this.messageBus.publish({
           type: MessageBusType.UPDATE_POLICY,
@@ -206,7 +205,7 @@ export abstract class BaseToolInvocation<
           timeoutId = undefined;
         }
         abortSignal.removeEventListener('abort', abortHandler);
-        this.messageBus?.unsubscribe(
+        this.messageBus.unsubscribe(
           MessageBusType.TOOL_CONFIRMATION_RESPONSE,
           responseHandler,
         );
@@ -341,9 +340,9 @@ export abstract class DeclarativeTool<
     readonly description: string,
     readonly kind: Kind,
     readonly parameterSchema: unknown,
+    readonly messageBus: MessageBus,
     readonly isOutputMarkdown: boolean = true,
     readonly canUpdateOutput: boolean = false,
-    readonly messageBus?: MessageBus,
     readonly extensionName?: string,
     readonly extensionId?: string,
   ) {}
@@ -496,7 +495,7 @@ export abstract class BaseDeclarativeTool<
 
   protected abstract createInvocation(
     params: TParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<TParams, TResult>;

packages/core/src/tools/web-fetch.test.ts

@@ -10,6 +10,10 @@ import type { Config } from '../config/config.js';
 import { ApprovalMode } from '../policy/types.js';
 import { ToolConfirmationOutcome } from './tools.js';
 import { ToolErrorType } from './tool-error.js';
+import {
+  createMockMessageBus,
+  getMockMessageBusInstance,
+} from '../test-utils/mock-message-bus.js';
 import * as fetchUtils from '../utils/fetch.js';
 import { MessageBus } from '../confirmation-bus/message-bus.js';
 import { PolicyEngine } from '../policy/policy-engine.js';
@@ -126,9 +130,12 @@ describe('parsePrompt', () => {
 
 describe('WebFetchTool', () => {
   let mockConfig: Config;
+  let bus: MessageBus;
 
   beforeEach(() => {
     vi.resetAllMocks();
+    bus = createMockMessageBus();
+    getMockMessageBusInstance(bus).defaultToolDecision = 'ask_user';
     mockConfig = {
       getApprovalMode: vi.fn(),
       setApprovalMode: vi.fn(),
@@ -163,12 +170,12 @@ describe('WebFetchTool', () => {
         expectedError: 'Error(s) in prompt URLs:',
       },
     ])('should throw if $name', ({ prompt, expectedError }) => {
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       expect(() => tool.build({ prompt })).toThrow(expectedError);
     });
 
     it('should pass if prompt contains at least one valid URL', () => {
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       expect(() =>
         tool.build({ prompt: 'fetch https://example.com' }),
       ).not.toThrow();
@@ -181,7 +188,7 @@ describe('WebFetchTool', () => {
       vi.spyOn(fetchUtils, 'fetchWithTimeout').mockRejectedValue(
         new Error('fetch failed'),
       );
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://private.ip' };
       const invocation = tool.build(params);
       const result = await invocation.execute(new AbortController().signal);
@@ -191,7 +198,7 @@ describe('WebFetchTool', () => {
     it('should return WEB_FETCH_PROCESSING_ERROR on general processing failure', async () => {
       vi.spyOn(fetchUtils, 'isPrivateIp').mockReturnValue(false);
       mockGenerateContent.mockRejectedValue(new Error('API error'));
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://public.ip' };
       const invocation = tool.build(params);
       const result = await invocation.execute(new AbortController().signal);
@@ -209,7 +216,7 @@ describe('WebFetchTool', () => {
         candidates: [{ content: { parts: [{ text: 'fallback response' }] } }],
       });
 
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://private.ip' };
       const invocation = tool.build(params);
       await invocation.execute(new AbortController().signal);
@@ -237,7 +244,7 @@ describe('WebFetchTool', () => {
         candidates: [{ content: { parts: [{ text: 'fallback response' }] } }],
       });
 
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://public.ip' };
       const invocation = tool.build(params);
       await invocation.execute(new AbortController().signal);
@@ -306,7 +313,7 @@ describe('WebFetchTool', () => {
           ],
         }));
 
-        const tool = new WebFetchTool(mockConfig);
+        const tool = new WebFetchTool(mockConfig, bus);
         const params = { prompt: 'fetch https://example.com' };
         const invocation = tool.build(params);
         const result = await invocation.execute(new AbortController().signal);
@@ -330,7 +337,7 @@ describe('WebFetchTool', () => {
 
   describe('shouldConfirmExecute', () => {
     it('should return confirmation details with the correct prompt and parsed urls', async () => {
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://example.com' };
       const invocation = tool.build(params);
       const confirmationDetails = await invocation.shouldConfirmExecute(
@@ -347,7 +354,7 @@ describe('WebFetchTool', () => {
     });
 
     it('should convert github urls to raw format', async () => {
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = {
         prompt:
           'fetch https://github.com/google/gemini-react/blob/main/README.md',
@@ -373,7 +380,7 @@ describe('WebFetchTool', () => {
       vi.spyOn(mockConfig, 'getApprovalMode').mockReturnValue(
         ApprovalMode.AUTO_EDIT,
       );
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://example.com' };
       const invocation = tool.build(params);
       const confirmationDetails = await invocation.shouldConfirmExecute(
@@ -384,7 +391,7 @@ describe('WebFetchTool', () => {
     });
 
     it('should call setApprovalMode when onConfirm is called with ProceedAlways', async () => {
-      const tool = new WebFetchTool(mockConfig);
+      const tool = new WebFetchTool(mockConfig, bus);
       const params = { prompt: 'fetch https://example.com' };
       const invocation = tool.build(params);
       const confirmationDetails = await invocation.shouldConfirmExecute(
@@ -412,8 +419,8 @@ describe('WebFetchTool', () => {
     let messageBus: MessageBus;
     let mockUUID: Mock;
 
-    const createToolWithMessageBus = (bus?: MessageBus) => {
-      const tool = new WebFetchTool(mockConfig, bus);
+    const createToolWithMessageBus = (customBus?: MessageBus) => {
+      const tool = new WebFetchTool(mockConfig, customBus ?? bus);
       const params = { prompt: 'fetch https://example.com' };
       return { tool, invocation: tool.build(params) };
     };
@@ -516,16 +523,6 @@ describe('WebFetchTool', () => {
       );
     });
 
-    it('should fall back to legacy confirmation when no message bus', async () => {
-      const { invocation } = createToolWithMessageBus(); // No message bus
-      const result = await invocation.shouldConfirmExecute(
-        new AbortController().signal,
-      );
-
-      expect(result).not.toBe(false);
-      expect(result).toHaveProperty('type', 'info');
-    });
-
     it('should ignore responses with wrong correlation ID', async () => {
       vi.useFakeTimers();
       const { invocation } = createToolWithMessageBus(messageBus);

packages/core/src/tools/web-fetch.ts

@@ -114,7 +114,7 @@ class WebFetchToolInvocation extends BaseToolInvocation<
   constructor(
     private readonly config: Config,
     params: WebFetchToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -218,7 +218,8 @@ ${textContent}
   protected override async getConfirmationDetails(
     _abortSignal: AbortSignal,
   ): Promise<ToolCallConfirmationDetails | false> {
-    // Legacy confirmation flow (no message bus OR policy decision was ASK_USER)
+    // Check for AUTO_EDIT approval mode. This tool has a specific behavior
+    // where ProceedAlways switches the entire session to AUTO_EDIT.
     if (this.config.getApprovalMode() === ApprovalMode.AUTO_EDIT) {
       return false;
     }
@@ -406,7 +407,7 @@ export class WebFetchTool extends BaseDeclarativeTool<
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       WebFetchTool.Name,
@@ -424,9 +425,9 @@ export class WebFetchTool extends BaseDeclarativeTool<
         required: ['prompt'],
         type: 'object',
       },
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
   }
 
@@ -452,14 +453,14 @@ export class WebFetchTool extends BaseDeclarativeTool<
 
   protected createInvocation(
     params: WebFetchToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<WebFetchToolParams, ToolResult> {
     return new WebFetchToolInvocation(
       this.config,
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _toolDisplayName,
     );

packages/core/src/tools/web-search.test.ts

@@ -11,6 +11,7 @@ import { WebSearchTool } from './web-search.js';
 import type { Config } from '../config/config.js';
 import { GeminiClient } from '../core/client.js';
 import { ToolErrorType } from './tool-error.js';
+import { createMockMessageBus } from '../test-utils/mock-message-bus.js';
 
 // Mock GeminiClient and Config constructor
 vi.mock('../core/client.js');
@@ -33,7 +34,7 @@ describe('WebSearchTool', () => {
       },
     } as unknown as Config;
     mockGeminiClient = new GeminiClient(mockConfigInstance);
-    tool = new WebSearchTool(mockConfigInstance);
+    tool = new WebSearchTool(mockConfigInstance, createMockMessageBus());
   });
 
   afterEach(() => {

packages/core/src/tools/web-search.ts

@@ -65,7 +65,7 @@ class WebSearchToolInvocation extends BaseToolInvocation<
   constructor(
     private readonly config: Config,
     params: WebSearchToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -192,7 +192,7 @@ export class WebSearchTool extends BaseDeclarativeTool<
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       WebSearchTool.Name,
@@ -209,9 +209,9 @@ export class WebSearchTool extends BaseDeclarativeTool<
         },
         required: ['query'],
       },
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
   }
 
@@ -231,7 +231,7 @@ export class WebSearchTool extends BaseDeclarativeTool<
 
   protected createInvocation(
     params: WebSearchToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ): ToolInvocation<WebSearchToolParams, WebSearchToolResult> {

packages/core/src/tools/write-file.ts

@@ -149,7 +149,7 @@ class WriteFileToolInvocation extends BaseToolInvocation<
   constructor(
     private readonly config: Config,
     params: WriteFileToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     toolName?: string,
     displayName?: string,
   ) {
@@ -409,7 +409,7 @@ export class WriteFileTool
 
   constructor(
     private readonly config: Config,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ) {
     super(
       WriteFileTool.Name,
@@ -432,9 +432,9 @@ export class WriteFileTool
         required: ['file_path', 'content'],
         type: 'object',
       },
+      messageBus,
       true,
       false,
-      messageBus,
     );
   }
 
@@ -475,7 +475,7 @@ export class WriteFileTool
 
   protected createInvocation(
     params: WriteFileToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
   ): ToolInvocation<WriteFileToolParams, ToolResult> {
     return new WriteFileToolInvocation(
       this.config,

packages/core/src/tools/write-todos.test.ts

@@ -6,9 +6,10 @@
 
 import { describe, expect, it } from 'vitest';
 import { WriteTodosTool, type WriteTodosToolParams } from './write-todos.js';
+import { createMockMessageBus } from '../test-utils/mock-message-bus.js';
 
 describe('WriteTodosTool', () => {
-  const tool = new WriteTodosTool();
+  const tool = new WriteTodosTool(createMockMessageBus());
   const signal = new AbortController().signal;
 
   describe('validation', () => {

packages/core/src/tools/write-todos.ts

@@ -101,7 +101,7 @@ class WriteTodosToolInvocation extends BaseToolInvocation<
 > {
   constructor(
     params: WriteTodosToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _toolDisplayName?: string,
   ) {
@@ -145,7 +145,7 @@ export class WriteTodosTool extends BaseDeclarativeTool<
 > {
   static readonly Name = WRITE_TODOS_TOOL_NAME;
 
-  constructor(messageBus?: MessageBus) {
+  constructor(messageBus: MessageBus) {
     super(
       WriteTodosTool.Name,
       'WriteTodos',
@@ -180,9 +180,9 @@ export class WriteTodosTool extends BaseDeclarativeTool<
         required: ['todos'],
         additionalProperties: false,
       },
+      messageBus,
       true, // isOutputMarkdown
       false, // canUpdateOutput
-      messageBus,
     );
   }
 
@@ -251,13 +251,13 @@ export class WriteTodosTool extends BaseDeclarativeTool<
 
   protected createInvocation(
     params: WriteTodosToolParams,
-    messageBus?: MessageBus,
+    messageBus: MessageBus,
     _toolName?: string,
     _displayName?: string,
   ): ToolInvocation<WriteTodosToolParams, ToolResult> {
     return new WriteTodosToolInvocation(
       params,
-      messageBus ?? this.messageBus,
+      messageBus,
       _toolName,
       _displayName,
     );