Vercel AI SDK

// app/api/flow/route.ts (Next.js)
// npm install @flow-engineer/messaging ai @ai-sdk/openai
import { after } from "next/server";
import { FlowMessaging, contentText } from "@flow-engineer/messaging";
import { streamText, type ModelMessage } from "ai";
import { openai } from "@ai-sdk/openai";

const flow = new FlowMessaging();

export const POST = flow.webhooks.handler({
  onEvent: async (event) => {
    if (event.type !== "message.received") return;

    after(async () => {
      // The last 20 messages of this conversation, oldest first (the new one included).
      const page = await event.conversation.messages({ limit: 20 });
      const messages: ModelMessage[] = page.data
        .reverse()
        .map((m) => ({ role: m.direction === "in" ? "user" : "assistant", content: contentText(m.content) }) as ModelMessage)
        .filter((m) => m.content);

      const result = streamText({
        model: openai("gpt-4.1-mini"),
        system: "You are the assistant for Asha's Bakery. Answer in short messages.",
        messages,
      });
      await event.conversation.reply(result, { idempotencyKey: event.id });
    });
  },
});