fix: rehydrate canvas chat history reliably on initial open

components/canvas/CanvasChatPanel.tsx

@@ -597,6 +597,7 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
   const autoContextRef = useRef<string | null>(null);
   const pendingLaunchRef = useRef<CanvasLaunchPayload | null>(null);
   const sessionMenuRef = useRef<HTMLDivElement>(null);
+  const historyScrollTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   
   // 🆕 标签悬停预览状态
   const [tagPreview, setTagPreview] = useState<TagPreviewInfo | null>(null);
@@ -1597,15 +1598,41 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
     }
   }, [selectedModelId, status, sendMessage, clearSelection]);
   
-  // 当历史消息加载完成后，更新消息列表
-  const hasLoadedHistory = useRef(false);
+  // 当历史消息加载完成后，更新消息列表（支持同一会话的增量刷新）
+  const loadedHistorySignatureRef = useRef<string>("");
   useEffect(() => {
-    if (historyData && !hasLoadedHistory.current) {
-      hasLoadedHistory.current = true;
-      setMessages(historyData.messages || []);
-      console.log('[CanvasChat] 已加载历史消息:', historyData.messages?.length || 0);
+    if (historyScrollTimerRef.current) {
+      clearTimeout(historyScrollTimerRef.current);
+      historyScrollTimerRef.current = null;
     }
-  }, [historyData, setMessages]);
+
+    if (!historyData || !rawChatId) return;
+    if (status === "streaming" || status === "submitted") return;
+
+    const historyMessages = historyData.messages || [];
+    const lastMessageId = historyMessages.at(-1)?.id || "none";
+    const signature = `${rawChatId}:${historyMessages.length}:${lastMessageId}`;
+
+    if (loadedHistorySignatureRef.current === signature) return;
+
+    loadedHistorySignatureRef.current = signature;
+    setMessages(historyMessages);
+    console.log("[CanvasChat] 已同步历史消息:", historyMessages.length, signature);
+
+    requestAnimationFrame(() => {
+      messagesEndRef.current?.scrollIntoView({ behavior: "auto", block: "end" });
+    });
+    historyScrollTimerRef.current = setTimeout(() => {
+      messagesEndRef.current?.scrollIntoView({ behavior: "auto", block: "end" });
+      historyScrollTimerRef.current = null;
+    }, 160);
+    return () => {
+      if (historyScrollTimerRef.current) {
+        clearTimeout(historyScrollTimerRef.current);
+        historyScrollTimerRef.current = null;
+      }
+    };
+  }, [historyData, rawChatId, setMessages, status]);
 
   // 监听消息变化，提取图片并添加到画布
   // 只处理新生成的图片，不处理历史消息中的图片
@@ -1613,7 +1640,7 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
   const isInitialLoad = useRef(true);
 
   useEffect(() => {
-    hasLoadedHistory.current = false;
+    loadedHistorySignatureRef.current = "";
     processedMessageIds.current.clear();
     isInitialLoad.current = true;
     hiddenPromptRef.current = null;
@@ -3175,6 +3202,14 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
               }
               return part;
             });
+
+            const fallbackContent =
+              typeof (message as any).content === "string"
+                ? (message as any).content.trim()
+                : "";
+            if (cleanedParts.length === 0 && fallbackContent) {
+              cleanedParts.push({ type: "text", text: fallbackContent } as any);
+            }
             
             // 检查清理后是否有实际内容（更严格的检查）
             let hasContent = false;