feat(R3): deduplicate UI cards by card_id (loading → complete merge)

Cards with the same card_id in props are deduplicated to show only the
last (complete) version, replacing any earlier loading skeleton cards.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

langgraph/src/main.tsx

@@ -24,6 +24,23 @@ import ToolCallStatus from "@/components/ToolCallStatus.tsx";
 const LANGGRAPH_URL =
   import.meta.env.VITE_LANGGRAPH_URL ?? "http://localhost:2024";
 
+// ─── Card deduplication by card_id ──────────────────────────────────────────
+// When the backend pushes loading then complete cards with the same card_id,
+// keep only the last (most recent) card per card_id. Cards without card_id pass through.
+function deduplicateUiItems(items: UIMsgLocal[]): UIMsgLocal[] {
+  const seen = new Map<string, number>();
+  // Walk forward to find the last index for each card_id
+  items.forEach((item, idx) => {
+    const cardId = item.props?.card_id as string | undefined;
+    if (cardId) seen.set(cardId, idx);
+  });
+  return items.filter((item, idx) => {
+    const cardId = item.props?.card_id as string | undefined;
+    if (!cardId) return true;
+    return seen.get(cardId) === idx;
+  });
+}
+
 // ─── Tool groups ────────────────────────────────────────────────────────────
 const TOOL_GROUPS = [
   { key: "knowledge", label: "知识库", icon: BookOpen, tools: ["kb_search"] },
@@ -419,9 +436,11 @@ function App() {
           {thread.messages.map((message, idx) => {
             // Render UI cards attached to this message
             // eslint-disable-next-line @typescript-eslint/no-explicit-any
-            const uiItems = ((thread.values as any)?.ui ?? []).filter(
-              (ui: UIMsgLocal) => ui.metadata?.message_id === message.id,
-            ) as UIMsgLocal[];
+            const uiItems = deduplicateUiItems(
+              ((thread.values as any)?.ui ?? []).filter(
+                (ui: UIMsgLocal) => ui.metadata?.message_id === message.id,
+              ) as UIMsgLocal[]
+            );
 
             if (message.type === "human") {
               const humanText = typeof message.content === "string"
@@ -565,13 +584,14 @@ function App() {
 
           {/* Streaming UI cards not yet attached to a completed message */}
           {thread.isLoading &&
-            (thread.values?.ui ?? [])
-              .filter((ui: UIMsgLocal) => {
+            deduplicateUiItems(
+              (thread.values?.ui ?? []).filter((ui: UIMsgLocal) => {
                 const attachedToExisting = thread.messages.some(
                   (m) => m.id === ui.metadata?.message_id,
                 );
                 return !attachedToExisting;
               })
+            )
               .map((ui: UIMsgLocal) => (
                 <LoadExternalComponent
                   key={ui.id}