fix: persist greeting fast path safely

app/(chat)/api/chat/route.ts

@@ -4834,6 +4834,23 @@ export async function POST(request: Request) {
       }
 
       const greetingMessage = "你好，我在。你可以直接告诉我想做什么：生图、修图、生成视频、分析图片都可以。";
+      const fastPathTitle = requestTextContent.trim().slice(0, 80) || "新对话";
+      await saveChat({
+        id,
+        userId: session.user.id,
+        title: fastPathTitle,
+        visibility: selectedVisibilityType,
+      });
+
+      const greetingChat = await findChatWithRetry(id);
+      if (!greetingChat) {
+        throw new ChatSDKError("bad_request:database", "Failed to save chat");
+      }
+
+      if (greetingChat.userId !== session.user.id) {
+        return new ChatSDKError("forbidden:chat").toResponse();
+      }
+
       const greetingStream = createUIMessageStream({
         execute: async ({ writer }) => {
           const messageId = generateUUID();
@@ -4841,6 +4858,19 @@ export async function POST(request: Request) {
 
           await saveMessages({
             messages: [
+              {
+                id: message.id,
+                chatId: id,
+                role: "user",
+                parts: message.parts as any,
+                attachments: [],
+                createdAt: new Date(),
+                videoStorageStatus: null,
+                temporaryVideoUrl: null,
+                permanentVideoUrl: null,
+                archivedAt: null,
+                videoMetadata: null,
+              },
               {
                 id: messageId,
                 chatId: id,

lib/db/queries.ts

@@ -326,7 +326,9 @@ export async function getChatById({ id }: { id: string }) {
 
 export async function saveMessages({ messages }: { messages: DBMessage[] }) {
   try {
-    return await db.insert(message).values(messages);
+    return await db.insert(message).values(messages).onConflictDoNothing({
+      target: message.id,
+    });
   } catch (_error) {
     throw new ChatSDKError("bad_request:database", "Failed to save messages");
   }