refactor(DATAGO-124692): add persistent SSE event buffer for background task replay

client/webui/frontend/src/lib/components/chat/SessionList.tsx

@@ -37,10 +37,13 @@ const SessionName: React.FC<SessionNameProps> = ({ session, respondingSessionId
             return false; // No pulse when auto title generation is disabled
         }
         const isNewChat = !session.name || session.name === "New Chat";
-        // Only pulse if this session is the one that started the response
+        // Pulse if this session is the one that started the response
         const isThisSessionResponding = respondingSessionId === session.id;
-        return isThisSessionResponding && isNewChat;
-    }, [session.name, session.id, respondingSessionId, isGenerating, autoTitleGenerationEnabled]);
+        // Also pulse if this session has a running background task and no title yet
+        // This handles the case where user switched away while task is running
+        const hasBackgroundTaskWithNewTitle = session.hasRunningBackgroundTask && isNewChat;
+        return (isThisSessionResponding && isNewChat) || hasBackgroundTaskWithNewTitle;
+    }, [session.name, session.id, respondingSessionId, isGenerating, autoTitleGenerationEnabled, session.hasRunningBackgroundTask]);
 
     // Show slow pulse while waiting for title, faster pulse during transition animation
     const animationClass = useMemo(() => {

client/webui/frontend/src/lib/hooks/useBackgroundTaskMonitor.ts

@@ -1,3 +1,8 @@
+/**
+ * Hook for monitoring and reconnecting to background tasks.
+ * Stores active background tasks in localStorage and automatically reconnects on session load.
+ */
+
 import { useState, useEffect, useCallback, useRef } from "react";
 import { api } from "@/lib/api";
 import type { BackgroundTaskState, BackgroundTaskStatusResponse, ActiveBackgroundTasksResponse, BackgroundTaskNotification } from "@/lib/types/background-tasks";
@@ -17,8 +22,8 @@ interface UseBackgroundTaskMonitorProps {
  */
 export function useBackgroundTaskMonitor({ userId, onTaskCompleted, onTaskFailed }: UseBackgroundTaskMonitorProps) {
     const [backgroundTasks, setBackgroundTasks] = useState<BackgroundTaskState[]>([]);
+    const backgroundTasksRef = useRef<BackgroundTaskState[]>(backgroundTasks);
     const [notifications, setNotifications] = useState<BackgroundTaskNotification[]>([]);
-    const backgroundTasksRef = useRef<BackgroundTaskState[]>([]);
 
     // Load background tasks from localStorage on mount
     useEffect(() => {
@@ -34,6 +39,11 @@ export function useBackgroundTaskMonitor({ userId, onTaskCompleted, onTaskFailed
         }
     }, []);
 
+    // Keep the ref in sync with state
+    useEffect(() => {
+        backgroundTasksRef.current = backgroundTasks;
+    }, [backgroundTasks]);
+
     // Save background tasks to localStorage whenever they change
     useEffect(() => {
         if (backgroundTasks.length > 0) {
@@ -101,6 +111,7 @@ export function useBackgroundTaskMonitor({ userId, onTaskCompleted, onTaskFailed
     );
 
     // Check all background tasks and update their status
+    // Uses backgroundTasksRef to read current tasks, making this callback stable
     const checkAllBackgroundTasks = useCallback(async () => {
         const tasks = backgroundTasksRef.current;
         if (tasks.length === 0) {
@@ -202,6 +213,7 @@ export function useBackgroundTaskMonitor({ userId, onTaskCompleted, onTaskFailed
     // Periodic checking to detect background task completion when not connected to SSE
     // This handles the case where a task completes while the user is on a different session
     const hasBackgroundTasks = backgroundTasks.length > 0;
+
     useEffect(() => {
         if (!hasBackgroundTasks) {
             return;

client/webui/frontend/src/lib/hooks/useBeforeUnload.ts

@@ -3,15 +3,25 @@ import { useChatContext } from "./useChatContext";
 import { useConfigContext } from "./useConfigContext";
 
 export function useBeforeUnload() {
-    const { messages } = useChatContext();
+    const { messages, isResponding } = useChatContext();
     const config = useConfigContext();
 
     /**
      * Cross-browser beforeunload event handler
-     * Only warns when persistence is disabled and messages exist
+     * Warns when:
+     * 1. Persistence is disabled and messages exist (chat history would be lost)
+     * 2. A task is running and background tasks are disabled (task results would be lost)
      */
     const handleBeforeUnload = useCallback(
         (event: BeforeUnloadEvent): string | void => {
+            // Case 1: Task is running and background tasks are disabled
+            // In this case, navigating away may cause the user to lose the task results
+            if (isResponding && config?.backgroundTasksEnabled === false) {
+                event.preventDefault();
+                return "A task is currently running. If you leave now, you may lose the response. Are you sure you want to leave?";
+            }
+
+            // Case 2: Persistence disabled and messages exist (original behavior)
             if (config?.persistenceEnabled !== false) {
                 return;
             }
@@ -24,7 +34,7 @@ export function useBeforeUnload() {
 
             return "Are you sure you want to leave? Your chat history will be lost.";
         },
-        [messages.length, config?.persistenceEnabled]
+        [messages.length, config?.persistenceEnabled, config?.backgroundTasksEnabled, isResponding]
     );
 
     /**

client/webui/frontend/src/lib/hooks/useTitleGeneration.ts

@@ -35,7 +35,7 @@ export const useTitleGeneration = () => {
                 }
             }
 
-            console.log(`[useTitleGeneration] Initial title: "${initialTitle}"`);
+            console.debug(`[useTitleGeneration] Initial title: "${initialTitle}"`);
 
             // Dispatch event to indicate title generation is starting
             if (typeof window !== "undefined") {
@@ -66,7 +66,7 @@ export const useTitleGeneration = () => {
                 return;
             }
 
-            console.log("[useTitleGeneration] Title generation triggered, polling for update...");
+            console.debug("[useTitleGeneration] Title generation triggered, polling for update...");
 
             // Poll for title update with exponential backoff
             const pollForTitle = async () => {