📄 ai-sdk/cookbook/api-servers/express

import { openai } from '@ai-sdk/openai';import { streamText } from 'ai';import express, { Request, Response } from 'express';
const app = express();
app.post('/', async (req: Request, res: Response) => {  const result = streamText({    model: openai('gpt-4o'),    prompt: 'Invent a new holiday and describe its traditions.',  });
  result.pipeUIMessageStreamToResponse(res);});
app.listen(8080, () => {  console.log(`Example app listening on port ${8080}`);});

Sending Custom Data

pipeUIMessageStreamToResponse can be used to send custom data to the client.

index.ts

import { openai } from '@ai-sdk/openai';import {  createUIMessageStream,  pipeUIMessageStreamToResponse,  streamText,} from 'ai';import express, { Request, Response } from 'express';
const app = express();
app.post('/custom-data-parts', async (req: Request, res: Response) => {  pipeUIMessageStreamToResponse({    response: res,    stream: createUIMessageStream({      execute: async ({ writer }) => {        writer.write({ type: 'start' });
        writer.write({          type: 'data-custom',          data: {            custom: 'Hello, world!',          },        });
        const result = streamText({          model: openai('gpt-4o'),          prompt: 'Invent a new holiday and describe its traditions.',        });
        writer.merge(result.toUIMessageStream({ sendStart: false }));      },    }),  });});
app.listen(8080, () => {  console.log(`Example app listening on port ${8080}`);});

Text Stream

You can send a text stream to the client using pipeTextStreamToResponse.

index.ts

import { openai } from '@ai-sdk/openai';import { streamText } from 'ai';import express, { Request, Response } from 'express';
const app = express();
app.post('/', async (req: Request, res: Response) => {  const result = streamText({    model: openai('gpt-4o'),    prompt: 'Invent a new holiday and describe its traditions.',  });
  result.pipeTextStreamToResponse(res);});
app.listen(8080, () => {  console.log(`Example app listening on port ${8080}`);});

Troubleshooting

Streaming not working when proxied

On this page

Deploy and Scale AI Apps with Vercel.

Vercel delivers the infrastructure and developer experience you need to ship reliable AI-powered applications at scale.

Trusted by industry leaders:

OpenAI
Photoroom

Talk to an expert