fix: stabilize live activity updates

frontend/app/components/assistant-ui/activity-panel.tsx

@@ -165,20 +165,29 @@ export function ActivityPanel({ asDrawer = false }: { asDrawer?: boolean } = {})
 		() => collectLiveRunItems(liveRunStatus),
 		[liveRunStatus],
 	);
-	const selectedMessageId = selectedId ? activityMessageId(selectedId) : null;
 	const liveRunActive = hasActiveRun(liveRunStatus) && liveItems.length > 0;
+	const mergedItems = useMemo(
+		() =>
+			liveRunActive
+				? mergeActivityItems(messageItems, liveItems)
+				: messageItems,
+		[liveRunActive, messageItems, liveItems],
+	);
+	const selectedMessageId = selectedId ? activityMessageId(selectedId) : null;
 	const selectedMessageItems = selectedMessageId
-		? messageItems.filter(
+		? mergedItems.filter(
 				(item) => activityMessageId(item.id) === selectedMessageId,
 			)
 		: [];
 	const shouldUseLiveItems = Boolean(activeSessionId && liveRunActive);
-	const items = shouldUseLiveItems ? liveItems : messageItems;
+	const items = shouldUseLiveItems ? mergedItems : messageItems;
 	const selectedItems = selectedMessageId
 		? items.filter((item) => activityMessageId(item.id) === selectedMessageId)
 		: [];
 	const visibleItems = shouldUseLiveItems
-		? liveItems
+		? selectedMessageId && selectedMessageItems.length > 0
+			? selectedMessageItems
+			: items
 		: selectedMessageId && selectedMessageItems.length > 0
 			? selectedMessageItems
 			: selectedMessageId && selectedItems.length > 0
@@ -1013,6 +1022,37 @@ function collectLiveRunItems(runStatus: ClawRunStatus | null) {
 	return items;
 }
 
+function mergeActivityItems(
+	messageItems: readonly ActivityItem[],
+	liveItems: readonly ActivityItem[],
+) {
+	if (!liveItems.length) return [...messageItems];
+	if (!messageItems.length) return [...liveItems];
+	const merged = [...messageItems];
+	const seen = new Set(
+		messageItems.map((item) =>
+			[
+				item.kind,
+				item.title,
+				item.argsText ?? "",
+				item.summary,
+			].join("\u0000"),
+		),
+	);
+	for (const item of liveItems) {
+		const key = [
+			item.kind,
+			item.title,
+			item.argsText ?? "",
+			item.summary,
+		].join("\u0000");
+		if (seen.has(key)) continue;
+		seen.add(key);
+		merged.push(item);
+	}
+	return merged;
+}
+
 function summarizeLiveRunEvents(
 	runStatus: ClawRunStatus,
 	events: readonly LiveRunEvent[],