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

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -36,6 +36,7 @@ import {
   CoreToolCallStatus,
   buildUserSteeringHintPrompt,
   generateSteeringAckMessage,
+  getPlanModeExitMessage,
 } from '@google/gemini-cli-core';
 import type {
   Config,
@@ -203,6 +204,9 @@ export const useGeminiStream = (
   const abortControllerRef = useRef<AbortController | null>(null);
   const turnCancelledRef = useRef(false);
   const activeQueryIdRef = useRef<string | null>(null);
+  const previousApprovalModeRef = useRef<ApprovalMode>(
+    config.getApprovalMode(),
+  );
   const [isResponding, setIsResponding] = useState<boolean>(false);
   const [thought, thoughtRef, setThought] =
     useStateAndRef<ThoughtSummary | null>(null);
@@ -1435,6 +1439,34 @@ export const useGeminiStream = (
 
   const handleApprovalModeChange = useCallback(
     async (newApprovalMode: ApprovalMode) => {
+      if (
+        previousApprovalModeRef.current === ApprovalMode.PLAN &&
+        newApprovalMode !== ApprovalMode.PLAN &&
+        streamingState === StreamingState.Idle
+      ) {
+        if (geminiClient) {
+          try {
+            await geminiClient.addHistory({
+              role: 'user',
+              parts: [
+                {
+                  text: getPlanModeExitMessage(newApprovalMode, true),
+                },
+              ],
+            });
+          } catch (error) {
+            onDebugMessage(
+              `Failed to notify model of Plan Mode exit: ${getErrorMessage(error)}`,
+            );
+            addItem({
+              type: MessageType.ERROR,
+              text: 'Failed to update the model about exiting Plan Mode. The model might be out of sync. Please consider restarting the session if you see unexpected behavior.',
+            });
+          }
+        }
+      }
+      previousApprovalModeRef.current = newApprovalMode;
+
       // Auto-approve pending tool calls when switching to auto-approval modes
       if (
         newApprovalMode === ApprovalMode.YOLO ||
@@ -1473,7 +1505,7 @@ export const useGeminiStream = (
         }
       }
     },
-    [config, toolCalls],
+    [config, toolCalls, geminiClient, streamingState, addItem, onDebugMessage],
   );
 
   const handleCompletedTools = useCallback(