feat(plan): inject message when user manually exits Plan mode (#20203)

packages/core/src/index.ts

@@ -78,6 +78,7 @@ export * from './utils/authConsent.js';
 export * from './utils/googleQuotaErrors.js';
 export * from './utils/fileUtils.js';
 export * from './utils/planUtils.js';
+export * from './utils/approvalModeUtils.js';
 export * from './utils/fileDiffUtils.js';
 export * from './utils/retry.js';
 export * from './utils/shell-utils.js';

packages/core/src/tools/exit-plan-mode.ts

@@ -20,30 +20,12 @@ import type { Config } from '../config/config.js';
 import { EXIT_PLAN_MODE_TOOL_NAME } from './tool-names.js';
 import { validatePlanPath, validatePlanContent } from '../utils/planUtils.js';
 import { ApprovalMode } from '../policy/types.js';
-import { checkExhaustive } from '../utils/checks.js';
 import { resolveToRealPath, isSubpath } from '../utils/paths.js';
 import { logPlanExecution } from '../telemetry/loggers.js';
 import { PlanExecutionEvent } from '../telemetry/types.js';
 import { getExitPlanModeDefinition } from './definitions/coreTools.js';
 import { resolveToolDeclaration } from './definitions/resolver.js';
-
-/**
- * Returns a human-readable description for an approval mode.
- */
-function getApprovalModeDescription(mode: ApprovalMode): string {
-  switch (mode) {
-    case ApprovalMode.AUTO_EDIT:
-      return 'Auto-Edit mode (edits will be applied automatically)';
-    case ApprovalMode.DEFAULT:
-      return 'Default mode (edits will require confirmation)';
-    case ApprovalMode.YOLO:
-    case ApprovalMode.PLAN:
-      // YOLO and PLAN are not valid modes to enter when exiting plan mode
-      throw new Error(`Unexpected approval mode: ${mode}`);
-    default:
-      checkExhaustive(mode);
-  }
-}
+import { getPlanModeExitMessage } from '../utils/approvalModeUtils.js';
 
 export interface ExitPlanModeParams {
   plan_path: string;
@@ -222,15 +204,20 @@ export class ExitPlanModeInvocation extends BaseToolInvocation<
     const payload = this.approvalPayload;
     if (payload?.approved) {
       const newMode = payload.approvalMode ?? ApprovalMode.DEFAULT;
+
+      if (newMode === ApprovalMode.PLAN || newMode === ApprovalMode.YOLO) {
+        throw new Error(`Unexpected approval mode: ${newMode}`);
+      }
+
       this.config.setApprovalMode(newMode);
       this.config.setApprovedPlanPath(resolvedPlanPath);
 
       logPlanExecution(this.config, new PlanExecutionEvent(newMode));
 
-      const description = getApprovalModeDescription(newMode);
+      const exitMessage = getPlanModeExitMessage(newMode);
 
       return {
-        llmContent: `Plan approved. Switching to ${description}.
+        llmContent: `${exitMessage}
 
 The approved implementation plan is stored at: ${resolvedPlanPath}
 Read and follow the plan strictly during implementation.`,

packages/core/src/utils/approvalModeUtils.test.ts

@@ -0,0 +1,60 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { ApprovalMode } from '../policy/types.js';
+import {
+  getApprovalModeDescription,
+  getPlanModeExitMessage,
+} from './approvalModeUtils.js';
+
+describe('approvalModeUtils', () => {
+  describe('getApprovalModeDescription', () => {
+    it('should return correct description for DEFAULT mode', () => {
+      expect(getApprovalModeDescription(ApprovalMode.DEFAULT)).toBe(
+        'Default mode (edits will require confirmation)',
+      );
+    });
+
+    it('should return correct description for AUTO_EDIT mode', () => {
+      expect(getApprovalModeDescription(ApprovalMode.AUTO_EDIT)).toBe(
+        'Auto-Edit mode (edits will be applied automatically)',
+      );
+    });
+
+    it('should return correct description for PLAN mode', () => {
+      expect(getApprovalModeDescription(ApprovalMode.PLAN)).toBe(
+        'Plan mode (read-only planning)',
+      );
+    });
+
+    it('should return correct description for YOLO mode', () => {
+      expect(getApprovalModeDescription(ApprovalMode.YOLO)).toBe(
+        'YOLO mode (all tool calls auto-approved)',
+      );
+    });
+  });
+
+  describe('getPlanModeExitMessage', () => {
+    it('should return standard message when not manual', () => {
+      expect(getPlanModeExitMessage(ApprovalMode.DEFAULT, false)).toBe(
+        'Plan approved. Switching to Default mode (edits will require confirmation).',
+      );
+    });
+
+    it('should return manual message when manual is true', () => {
+      expect(getPlanModeExitMessage(ApprovalMode.AUTO_EDIT, true)).toBe(
+        'User has manually exited Plan Mode. Switching to Auto-Edit mode (edits will be applied automatically).',
+      );
+    });
+
+    it('should default to non-manual message', () => {
+      expect(getPlanModeExitMessage(ApprovalMode.YOLO)).toBe(
+        'Plan approved. Switching to YOLO mode (all tool calls auto-approved).',
+      );
+    });
+  });
+});

packages/core/src/utils/approvalModeUtils.ts

@@ -0,0 +1,40 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { ApprovalMode } from '../policy/types.js';
+import { checkExhaustive } from './checks.js';
+
+/**
+ * Returns a human-readable description for an approval mode.
+ */
+export function getApprovalModeDescription(mode: ApprovalMode): string {
+  switch (mode) {
+    case ApprovalMode.AUTO_EDIT:
+      return 'Auto-Edit mode (edits will be applied automatically)';
+    case ApprovalMode.DEFAULT:
+      return 'Default mode (edits will require confirmation)';
+    case ApprovalMode.PLAN:
+      return 'Plan mode (read-only planning)';
+    case ApprovalMode.YOLO:
+      return 'YOLO mode (all tool calls auto-approved)';
+    default:
+      return checkExhaustive(mode);
+  }
+}
+
+/**
+ * Generates a consistent message for plan mode transitions.
+ */
+export function getPlanModeExitMessage(
+  newMode: ApprovalMode,
+  isManual: boolean = false,
+): string {
+  const description = getApprovalModeDescription(newMode);
+  const prefix = isManual
+    ? 'User has manually exited Plan Mode.'
+    : 'Plan approved.';
+  return `${prefix} Switching to ${description}.`;
+}