diff --git a/langgraph/src/main.tsx b/langgraph/src/main.tsx
index 5bab780..a2aca46 100644
--- a/langgraph/src/main.tsx
+++ b/langgraph/src/main.tsx
@@ -112,6 +112,10 @@ function App() {
   const [currentThreadId, setCurrentThreadId] = useState<string | null>(null);
   const [sidebarOpen, setSidebarOpen] = useState(false);
 
+  // Historical messages fetched when switching to an existing thread
+  const [historicalMessages, setHistoricalMessages] = useState<Message[]>([]);
+  const [historicalUi, setHistoricalUi] = useState<UIMsgLocal[]>([]);
+
   // Canvas panel state
   const [canvasDoc, setCanvasDoc] = useState<CanvasDoc | null>(null);
 
@@ -243,7 +247,7 @@ function App() {
     setSidebarOpen(false);
   }, [currentThreadId, input]);
 
-  const handleSelectThread = useCallback((threadId: string) => {
+  const handleSelectThread = useCallback(async (threadId: string) => {
     // Save draft for current thread
     if (currentThreadId) {
       try { localStorage.setItem(`draft_${currentThreadId}`, input); } catch { /* ignore */ }
@@ -255,8 +259,22 @@ function App() {
     } catch {
       setInput("");
     }
+    // Clear historical messages before switching
+    setHistoricalMessages([]);
+    setHistoricalUi([]);
     setCurrentThreadId(threadId);
     setSidebarOpen(false);
+    // Fetch existing thread state so history is visible immediately
+    try {
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      const state = await (client.threads as any).getState(threadId);
+      if (state?.values?.messages) {
+        setHistoricalMessages(state.values.messages as Message[]);
+      }
+      if (state?.values?.ui) {
+        setHistoricalUi(state.values.ui as UIMsgLocal[]);
+      }
+    } catch { /* graceful degradation */ }
   }, [currentThreadId, input]);
 
   const handleDeleteThread = useCallback(async (threadId: string) => {
@@ -344,7 +362,7 @@ function App() {
     }
 
     // Auto-name thread on first message
-    const isFirstMessage = thread.messages.length === 0;
+    const isFirstMessage = activeMessages.length === 0;
 
     // Consume pending retry tool hint (set by soc:retry-tool event)
     const retryTool = pendingRetryToolRef.current;
@@ -418,7 +436,7 @@ function App() {
   // ── Regenerate last AI message ───────────────────────────────────────────
   function handleRegenerate() {
     // Find last human message
-    const humanMsgs = thread.messages.filter((m) => m.type === "human");
+    const humanMsgs = activeMessages.filter((m) => m.type === "human");
     const lastHuman = humanMsgs[humanMsgs.length - 1];
     if (!lastHuman || thread.isLoading) return;
 
@@ -471,9 +489,12 @@ function App() {
     reader.readAsDataURL(file);
   }
 
+  // ── Active messages: prefer streaming messages, fall back to historical ──
+  const activeMessages: Message[] = thread.messages.length > 0 ? thread.messages : historicalMessages;
+
   // ── Collect completed tool call IDs ─────────────────────────────────────
   const completedToolIds = new Set(
-    thread.messages
+    activeMessages
       .filter((m) => m.type === "tool")
       .map((m) => (m as any).tool_call_id as string)
       .filter(Boolean),
@@ -481,7 +502,7 @@ function App() {
 
   // ── Collect failed tool call IDs ─────────────────────────────────────────
   const failedToolIds = new Set(
-    thread.messages
+    activeMessages
       .filter((m) => m.type === "tool" && (m as any).status === "error")
       .map((m) => (m as any).tool_call_id as string)
       .filter(Boolean),
@@ -500,7 +521,7 @@ function App() {
   }>;
 
   // ── Find last AI message index ──────────────────────────────────────────
-  const lastAiIdx = thread.messages.reduce((last, m, i) => (m.type === "ai" ? i : last), -1);
+  const lastAiIdx = activeMessages.reduce((last, m, i) => (m.type === "ai" ? i : last), -1);
 
   return (
     <div className="h-screen flex flex-row bg-background text-foreground overflow-hidden">
@@ -566,7 +587,7 @@ function App() {
             setShowScrollBtn(el.scrollHeight - el.scrollTop - el.clientHeight > 200);
           }}
         >
-          {thread.messages.length === 0 && (
+          {activeMessages.length === 0 && (
             <div className="flex flex-col items-center justify-center h-full gap-4 text-muted-foreground select-none">
               <div className="flex flex-col items-center gap-2">
                 <p className="text-lg font-medium">你好，有什么可以帮你的？</p>
@@ -589,11 +610,14 @@ function App() {
             </div>
           )}
 
-          {thread.messages.map((message, idx) => {
+          {activeMessages.map((message, idx) => {
             // Render UI cards attached to this message
             // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            const allUi: UIMsgLocal[] = thread.messages.length > 0
+              ? ((thread.values as any)?.ui ?? [])
+              : historicalUi;
             const uiItemsRaw = deduplicateUiItems(
-              ((thread.values as any)?.ui ?? []).filter(
+              allUi.filter(
                 (ui: UIMsgLocal) => ui.metadata?.message_id === message.id,
               ) as UIMsgLocal[]
             );
@@ -779,7 +803,7 @@ function App() {
 
           {/* Loading placeholder: show 3-dot bounce when waiting for first AI tokens after a human message */}
           {(() => {
-            const lastMsg = thread.messages[thread.messages.length - 1];
+            const lastMsg = activeMessages[activeMessages.length - 1];
             const showLoadingDots = thread.isLoading && lastMsg?.type === "human";
             return showLoadingDots ? (
               <div className="flex items-center gap-1.5 px-4 py-3 rounded-2xl rounded-bl-sm bg-muted text-muted-foreground w-fit">
@@ -794,7 +818,7 @@ function App() {
           {thread.isLoading &&
             deduplicateUiItems(
               (thread.values?.ui ?? []).filter((ui: UIMsgLocal) => {
-                const attachedToExisting = thread.messages.some(
+                const attachedToExisting = activeMessages.some(
                   (m) => m.id === ui.metadata?.message_id,
                 );
                 return !attachedToExisting;