diff --git a/frontend/app/components/assistant-ui/activity-panel.tsx b/frontend/app/components/assistant-ui/activity-panel.tsx
index 8dff7df..561f028 100644
--- a/frontend/app/components/assistant-ui/activity-panel.tsx
+++ b/frontend/app/components/assistant-ui/activity-panel.tsx
@@ -120,13 +120,18 @@ export function ActivityPanel() {
 	const visibleItems = selectedMessageId
 		? items.filter((item) => activityMessageId(item.id) === selectedMessageId)
 		: items;
-	const prevCountRef = useRef(0);
+	const prevLatestIdRef = useRef<string | null>(null);
 
 	useEffect(() => {
-		if (mode === "activity" && items.length > prevCountRef.current) {
-			openItem(items.at(-1)?.id ?? items[0]?.id ?? "");
+		const latestId = items.at(-1)?.id ?? null;
+		if (
+			mode === "activity" &&
+			latestId &&
+			latestId !== prevLatestIdRef.current
+		) {
+			openItem(latestId);
 		}
-		prevCountRef.current = items.length;
+		prevLatestIdRef.current = latestId;
 	}, [items, mode, openItem]);
 
 	if (!open) return null;