diff --git a/packages/ui/src/components/chat/multi-task-chat.tsx b/packages/ui/src/components/chat/multi-task-chat.tsx
index e235361..8c15a74 100644
--- a/packages/ui/src/components/chat/multi-task-chat.tsx
+++ b/packages/ui/src/components/chat/multi-task-chat.tsx
@@ -97,6 +97,22 @@ export default function MultiTaskChat(props: MultiTaskChatProps) {
   // Message store integration
   const messageStore = () => messageStoreBus.getOrCreate(props.instanceId);
 
+  // Filter messages based on selected task - use store's session messages for the task session
+  // Must be defined before lastAssistantIndex which depends on it
+  const filteredMessageIds = createMemo(() => {
+    const task = selectedTask();
+    if (!task) return []; // Show no messages in Pipeline view
+
+    // If task has a dedicated session, get messages from the store for that session
+    if (task.taskSessionId) {
+      const store = messageStore();
+      return store.getSessionMessageIds(task.taskSessionId);
+    }
+
+    // Fallback to task.messageIds for backward compatibility
+    return task.messageIds || [];
+  });
+
   // Memoized to prevent recalculation on every render
   const lastAssistantIndex = createMemo(() => {
     const ids = filteredMessageIds();
@@ -117,21 +133,6 @@ export default function MultiTaskChat(props: MultiTaskChatProps) {
     return -1;
   });
 
-  // Filter messages based on selected task - use store's session messages for the task session
-  const filteredMessageIds = createMemo(() => {
-    const task = selectedTask();
-    if (!task) return []; // Show no messages in Pipeline view
-
-    // If task has a dedicated session, get messages from the store for that session
-    if (task.taskSessionId) {
-      const store = messageStore();
-      return store.getSessionMessageIds(task.taskSessionId);
-    }
-
-    // Fallback to task.messageIds for backward compatibility
-    return task.messageIds || [];
-  });
-
   // Note: Auto-scroll is handled in two places:
   // 1. After sending a message (in handleSendMessage)
   // 2. During streaming (in the isAgentThinking effect below)