fix: address PR feedback and background task lifecycle bugs

Addresses high-priority feedback from the automated code review tool regarding the logic error and inconsistency in `useAgentStream.ts` and `useExecutionLifecycle.ts`.

- `useAgentStream.ts`: Fixed `schedule_tool` fall-through by returning early if the command type is not `submit_prompt`. Prevented history duplication by only adding items not already handled by the slash command processor. Ensured the original raw string is logged.
- `useExecutionLifecycle.ts`: Removed `isActive` guards from the unmount cleanup effect and the `ExecutionLifecycleService.onBackground` listener to prevent background tasks from being incorrectly unsubscribed or missed when switching between Gemini and Agent streams.
- Updated `useAgentStream.test.tsx` to reflect the fixed history logic.

packages/cli/src/ui/hooks/useAgentStream.test.tsx

@@ -124,13 +124,6 @@ describe('useAgentStream', () => {
     expect(mockAgentProtocol.send).toHaveBeenCalledWith({
       message: { content: [{ type: 'text', text: 'modified prompt' }] },
     });
-    expect(mockAddItem).toHaveBeenCalledWith(
-      expect.objectContaining({
-        type: MessageType.USER,
-        text: 'modified prompt',
-      }),
-      expect.any(Number),
-    );
   });
 
   it('should update streamingState based on agent_start and agent_end events', async () => {

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

@@ -374,30 +374,44 @@ export const useAgentStream = ({
       let localQuery: PartListUnion = query;
 
       if (!options?.isContinuation) {
+        let shouldAddToHistory = true;
         if (typeof localQuery === 'string') {
           const trimmedQuery = localQuery.trim();
+          void logger?.logMessage(MessageSenderType.USER, trimmedQuery);
 
           if (isSlashCommand(trimmedQuery)) {
             const slashResult = await handleSlashCommand(trimmedQuery);
             if (slashResult) {
-              if (slashResult.type === 'handled') {
-                return;
-              }
               if (slashResult.type === 'submit_prompt') {
                 localQuery = slashResult.content;
+              } else if (slashResult.type === 'schedule_tool') {
+                addItem(
+                  {
+                    type: MessageType.ERROR,
+                    text: `The /${slashResult.toolName} command is not yet supported in Agent mode.`,
+                  },
+                  timestamp,
+                );
+                return;
+              } else {
+                // 'handled' or other types that don't need LLM submission
+                shouldAddToHistory = false;
               }
-              // schedule_tool is not yet supported in useAgentStream (mirrors handleAtCommand lack of support here)
             }
           }
         }
 
-        const queryText =
-          typeof localQuery === 'string'
-            ? localQuery
-            : partToString(localQuery);
+        if (shouldAddToHistory) {
+          const queryText =
+            typeof localQuery === 'string'
+              ? localQuery
+              : partToString(localQuery);
 
-        addItem({ type: MessageType.USER, text: queryText }, timestamp);
-        void logger?.logMessage(MessageSenderType.USER, queryText);
+          addItem({ type: MessageType.USER, text: queryText }, timestamp);
+          if (typeof localQuery !== 'string') {
+            void logger?.logMessage(MessageSenderType.USER, queryText);
+          }
+        }
         startNewPrompt();
       }
 

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

@@ -151,14 +151,13 @@ export const useExecutionLifecycle = (
 
   useEffect(
     () => () => {
-      if (!isActive) return;
       // Unsubscribe from all background task events on unmount
       for (const unsubscribe of m.subscriptions.values()) {
         unsubscribe();
       }
       m.subscriptions.clear();
     },
-    [m, isActive],
+    [m],
   );
 
   const toggleBackgroundTasks = useCallback(() => {
@@ -330,7 +329,6 @@ export const useExecutionLifecycle = (
   // ExecutionLifecycleService.createExecution() or attachExecution()
   // automatically gets Ctrl+B support — no UI changes needed per tool.
   useEffect(() => {
-    if (!isActive) return;
     const listener = (info: {
       executionId: number;
       label: string;
@@ -352,7 +350,7 @@ export const useExecutionLifecycle = (
     return () => {
       ExecutionLifecycleService.offBackground(listener);
     };
-  }, [registerBackgroundTask, m, isActive]);
+  }, [registerBackgroundTask, m]);
 
   const handleShellCommand = useCallback(
     (rawQuery: PartListUnion, abortSignal: AbortSignal): boolean => {