assistant-ui--assistant-ui/examples/with-livekit/app/api/chat/route.ts

import { openai } from "@ai-sdk/openai";
import {
  streamText,
  type UIMessage,
  convertToModelMessages,
  stepCountIs,
} from "ai";

export const maxDuration = 30;

export async function POST(req: Request) {
  const { messages }: { messages: UIMessage[] } = await req.json();

  const result = streamText({
    model: openai("gpt-5.4-nano"),
    messages: await convertToModelMessages(messages),
    stopWhen: stepCountIs(10),
  });

  return result.toUIMessageStreamResponse();
}