fix: complete session persistence overhaul (Codex 5.2)

1. Implemented auto-selection of tasks in MultiXV2 to prevent empty initial state.
2. Added force-loading logic for task session messages with debouncing.
3. Updated session-actions to return full assistant text and immediately persist native messages.
4. Fixed caching logic in instance-shell2 to retain active task sessions in memory.

packages/ui/src/components/chat/multix-v2/index.tsx

@@ -77,6 +77,8 @@ export default function MultiXV2(props: MultiXV2Props) {
     const [soloState, setSoloState] = createSignal({ isApex: false, isAutonomous: false, autoApproval: false, activeTaskId: null as string | null });
     const [lastAssistantIndex, setLastAssistantIndex] = createSignal(-1);
     const [bottomSentinel, setBottomSentinel] = createSignal<HTMLDivElement | null>(null);
+    const [hasUserSelection, setHasUserSelection] = createSignal(false);
+    const forcedLoadTimestamps = new Map<string, number>();
 
     // Helper to check if CURRENT task is sending
     const isSending = () => {
@@ -140,6 +142,10 @@ export default function MultiXV2(props: MultiXV2Props) {
                 setVisibleTasks(allTasks.filter(t => !t.archived));
                 // NOTE: Don't overwrite selectedTaskId from store - local state is authoritative
                 // This prevents the reactive cascade when the store updates
+                if (!selectedTaskId() && !hasUserSelection() && allTasks.length > 0) {
+                    const preferredId = session.activeTaskId || allTasks[0].id;
+                    setSelectedTaskIdLocal(preferredId);
+                }
             }
 
             // Get message IDs for currently selected task
@@ -149,6 +155,20 @@ export default function MultiXV2(props: MultiXV2Props) {
                 if (task) {
                     const store = getMessageStore();
                     if (task.taskSessionId) {
+                        const cachedIds = store.getSessionMessageIds(task.taskSessionId);
+                        if (cachedIds.length === 0) {
+                            const lastForced = forcedLoadTimestamps.get(task.taskSessionId) ?? 0;
+                            if (Date.now() - lastForced > 1000) {
+                                forcedLoadTimestamps.set(task.taskSessionId, Date.now());
+                                loadMessages(props.instanceId, task.taskSessionId, true).catch((error) =>
+                                    log.error("Failed to load task session messages", error)
+                                );
+                            }
+                        } else {
+                            loadMessages(props.instanceId, task.taskSessionId).catch((error) =>
+                                log.error("Failed to load task session messages", error)
+                            );
+                        }
                         setMessageIds(store.getSessionMessageIds(task.taskSessionId));
                     } else {
                         setMessageIds(task.messageIds || []);
@@ -251,6 +271,7 @@ export default function MultiXV2(props: MultiXV2Props) {
     const setSelectedTaskId = (id: string | null) => {
         // Update local state immediately (fast)
         setSelectedTaskIdLocal(id);
+        setHasUserSelection(true);
 
         // Immediately sync to load the new task's agent/model
         syncFromStore();
@@ -304,7 +325,7 @@ export default function MultiXV2(props: MultiXV2Props) {
                 syncFromStore();
 
                 // Set the selected task
-                setSelectedTaskIdLocal(taskId);
+                setSelectedTaskId(taskId);
 
                 const s = soloState();
                 if (s.isAutonomous) {
@@ -357,7 +378,7 @@ export default function MultiXV2(props: MultiXV2Props) {
         setTimeout(async () => {
             try {
                 const result = await addTask(props.instanceId, props.sessionId, title);
-                setSelectedTaskIdLocal(result.id);
+                setSelectedTaskId(result.id);
                 setTimeout(() => syncFromStore(), 50);
             } catch (error) {
                 log.error("handleCreateTask failed", error);

packages/ui/src/components/instance/instance-shell2.tsx

@@ -683,7 +683,25 @@ Now analyze the project and report your findings.`
   })
 
   const handleSessionSelect = (sessionId: string) => {
-    setActiveSession(props.instance.id, sessionId)
+    if (sessionId === "info") {
+      setActiveSession(props.instance.id, sessionId)
+      return
+    }
+
+    const instanceSessions = sessions().get(props.instance.id)
+    const session = instanceSessions?.get(sessionId)
+
+    if (session?.parentId) {
+      setActiveParentSession(props.instance.id, session.parentId)
+      const parentSession = instanceSessions?.get(session.parentId)
+      const matchingTask = parentSession?.tasks?.find((task) => task.taskSessionId === sessionId)
+      if (matchingTask) {
+        setActiveTask(props.instance.id, session.parentId, matchingTask.id)
+      }
+      return
+    }
+
+    setActiveParentSession(props.instance.id, sessionId)
   }
 
 
@@ -731,6 +749,7 @@ Now analyze the project and report your findings.`
     const sessionsMap = activeSessions()
     const parentId = parentSessionIdForInstance()
     const activeId = activeSessionIdForInstance()
+    const instanceSessions = sessions().get(props.instance.id)
     setCachedSessionIds((current) => {
       const next: string[] = []
       const append = (id: string | null) => {
@@ -743,6 +762,16 @@ Now analyze the project and report your findings.`
       append(parentId)
       append(activeId)
 
+      const parentSessionId = parentId || activeId
+      const parentSession = parentSessionId ? instanceSessions?.get(parentSessionId) : undefined
+      const activeTaskId = parentSession?.activeTaskId
+      if (activeTaskId && parentSession?.tasks?.length) {
+        const activeTask = parentSession.tasks.find((task) => task.id === activeTaskId)
+        if (activeTask?.taskSessionId) {
+          append(activeTask.taskSessionId)
+        }
+      }
+
       const limit = parentId ? SESSION_CACHE_LIMIT + 1 : SESSION_CACHE_LIMIT
       const trimmed = next.length > limit ? next.slice(0, limit) : next
       const trimmedSet = new Set(trimmed)