Nest.js

You can use the AI SDK in a Nest.js server to generate and stream text and objects to the client.

Examples

The examples show how to implement a Nest.js controller that uses the AI SDK to stream text and objects to the client.

Full example: github.com/vercel/ai/examples/nest

Data Stream

You can use the pipeDataStreamToResponse method to get a data 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.pipeDataStreamToResponse(res);
  }
}

Sending Custom Data

createDataStream 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 { createDataStream, streamText } from 'ai';
import { Response } from 'express';

@Controller()
export class AppController {
  @Post('/stream-data')
  async streamData(@Res() res: Response) {
    pipeDataStreamToResponse(res, {
      execute: async dataStreamWriter => {
        dataStreamWriter.writeData('initialized call');

        const result = streamText({
          model: openai('gpt-4o'),
          prompt: 'Invent a new holiday and describe its traditions.',
        });

        result.mergeIntoDataStream(dataStreamWriter);
      },
      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);
      },
    });
  }
}

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);
  }
}