Fix #1466: Resumable Streams

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

@@ -32,6 +32,7 @@ import {
   getChatById,
   getMessageCountByUserId,
   getMessagesByChatId,
+  getStreamIdsByChatId,
   saveChat,
   saveMessages,
   updateChatTitleById,
@@ -57,6 +58,63 @@ function getStreamContext() {
 
 export { getStreamContext };
 
+export async function GET(request: Request) {
+  const { searchParams } = new URL(request.url);
+  const chatId = searchParams.get("chatId");
+
+  if (!chatId) {
+    return new ChatbotError("bad_request:api").toResponse();
+  }
+
+  const session = await auth();
+
+  if (!session?.user) {
+    return new ChatbotError("unauthorized:chat").toResponse();
+  }
+
+  const chat = await getChatById({ id: chatId });
+
+  if (!chat) {
+    return new Response(null, { status: 204 });
+  }
+
+  if (chat.userId !== session.user.id) {
+    return new ChatbotError("forbidden:chat").toResponse();
+  }
+
+  const streamContext = getStreamContext();
+
+  if (!streamContext) {
+    return new Response(null, { status: 204 });
+  }
+
+  const streamIds = await getStreamIdsByChatId({ chatId });
+
+  if (!streamIds.length) {
+    return new Response(null, { status: 204 });
+  }
+
+  const recentStreamId = streamIds.at(-1);
+
+  if (!recentStreamId) {
+    return new Response(null, { status: 204 });
+  }
+
+  const emptyStream = new ReadableStream({
+    start(controller) {
+      controller.close();
+    },
+  });
+
+  return new Response(
+    await streamContext.resumeExistingStream(recentStreamId, emptyStream),
+    {
+      status: 200,
+      headers: { "Content-Type": "text/event-stream" },
+    }
+  );
+}
+
 export async function POST(request: Request) {
   let requestBody: PostRequestBody;
 

tests/e2e/api.test.ts

@@ -76,6 +76,22 @@ test.describe("Chat Error Handling", () => {
   });
 });
 
+test.describe("Resumable Streams", () => {
+  test("GET /api/chat returns 400 when chatId is missing", async ({
+    request,
+  }) => {
+    const response = await request.get("/api/chat");
+    expect(response.status()).toBe(400);
+  });
+
+  test("GET /api/chat returns 401 when not authenticated", async ({
+    request,
+  }) => {
+    const response = await request.get("/api/chat?chatId=nonexistent");
+    expect(response.status()).toBe(401);
+  });
+});
+
 test.describe("Suggested Actions", () => {
   test("suggested actions are clickable", async ({ page }) => {
     await page.goto("/");