📄 ai-sdk/cookbook/api-servers/nest

import { Controller, Post, Res } from '@nestjs/common';import { openai } from '@ai-sdk/openai';import { streamText } from 'ai';import { Response } from 'express';
@Controller()export class AppController {  @Post('/')  async root(@Res() res: Response) {    const result = streamText({      model: openai('gpt-4o'),      prompt: 'Invent a new holiday and describe its traditions.',    });
    result.pipeUIMessageStreamToResponse(res);  }}

Sending Custom Data

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

app.controller.ts

import { Controller, Post, Res } from '@nestjs/common';import { openai } from '@ai-sdk/openai';import {  createUIMessageStream,  streamText,  pipeUIMessageStreamToResponse,} from 'ai';import { Response } from 'express';
@Controller()export class AppController {  @Post('/stream-data')  async streamData(@Res() response: Response) {    const stream = createUIMessageStream({      execute: ({ writer }) => {        // write some data        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,            onError: error => {              // Error messages are masked by default for security reasons.              // If you want to expose the error message to the client, you can do so here:              return error instanceof Error ? error.message : String(error);            },          }),        );      },    });    pipeUIMessageStreamToResponse({ stream, response });  }}

Text Stream

You can use the pipeTextStreamToResponse method to get a text stream from the result and then pipe it to the response.

app.controller.ts

import { Controller, Post, Res } from '@nestjs/common';import { openai } from '@ai-sdk/openai';import { streamText } from 'ai';import { Response } from 'express';
@Controller()export class AppController {  @Post()  async example(@Res() res: Response) {    const result = streamText({      model: openai('gpt-4o'),      prompt: 'Invent a new holiday and describe its traditions.',    });
    result.pipeTextStreamToResponse(res);  }}

Troubleshooting

Streaming not working when proxied

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