# Nest.js

You can use the AI SDK in a [Nest.js](https://nestjs.com/) 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](https://github.com/vercel/ai/tree/main/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.

```ts filename='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

`pipeDataStreamToResponse` can be used to send custom data to the client.

```ts filename='app.controller.ts' highlight="10-12,19"
import { Controller, Post, Res } from '@nestjs/common';
import { openai } from '@ai-sdk/openai';
import { pipeDataStreamToResponse, 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.

```ts filename='app.controller.ts' highlight="15"
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](/docs/troubleshooting/streaming-not-working-when-proxied)


## Navigation

- [Node.js HTTP Server](/v4/cookbook/api-servers/node-http-server)
- [Express](/v4/cookbook/api-servers/express)
- [Hono](/v4/cookbook/api-servers/hono)
- [Fastify](/v4/cookbook/api-servers/fastify)
- [Nest.js](/v4/cookbook/api-servers/nest)


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