deepset-ai--haystack/docs-website/docs/pipeline-components/generators/transformerschatgenerator.mdx

---
title: "TransformersChatGenerator"
id: transformerschatgenerator
slug: "/transformerschatgenerator"
description: "Provides an interface for chat completion using a Hugging Face model that runs locally."
---

# TransformersChatGenerator

Provides an interface for chat completion using a Hugging Face model that runs locally.

<div className="key-value-table">

|  |  |
| --- | --- |
| **Most common position in a pipeline** | After a [ChatPromptBuilder](../builders/chatpromptbuilder.mdx)                                                         |
| **Mandatory init variables**           | None                                                                                                          |
| **Mandatory run variables**            | `messages`: A list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx) objects representing the chat or a plain string |
| **Output variables**                   | `replies`: A list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx) objects generated by the LLM |
| **API reference**                      | [Transformers](/reference/integrations-transformers)                                                                |
| **GitHub link**                        | https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/transformers |
| **Package name** | `transformers-haystack` |

</div>

## Overview

Keep in mind that if LLMs run locally, you may need a powerful machine to run them. This depends strongly on the model you select and its parameter count.

If a string is passed to `messages`, it is converted into a list containing a single `ChatMessage` with the `user` role.

Authentication with a Hugging Face API token is only required to access private or gated models. You can pass the token at initialization with `token`, or set the `HF_API_TOKEN` or `HF_TOKEN` environment variable:

```python
generator = TransformersChatGenerator(
    token=Secret.from_token("<your-api-key>"),
)
```

### Streaming

This Generator supports [streaming](guides-to-generators/choosing-the-right-generator.mdx#streaming-support) the tokens from the LLM directly in output. To do so, pass a function to the `streaming_callback` init parameter.

## Usage

Install the `transformers-haystack` package to use the `TransformersChatGenerator`:

```shell
pip install transformers-haystack
```

### On its own

```python
from haystack_integrations.components.generators.transformers import (
    TransformersChatGenerator,
)
from haystack.dataclasses import ChatMessage

generator = TransformersChatGenerator(model="Qwen/Qwen3-0.6B")
messages = [ChatMessage.from_user("What's Natural Language Processing? Be brief.")]
print(generator.run(messages))
```

### In a Pipeline

```python
from haystack import Pipeline
from haystack.components.builders.prompt_builder import ChatPromptBuilder
from haystack_integrations.components.generators.transformers import (
    TransformersChatGenerator,
)
from haystack.dataclasses import ChatMessage
from haystack.utils import Secret

prompt_builder = ChatPromptBuilder()
llm = TransformersChatGenerator(
    model="Qwen/Qwen3-0.6B",
    token=Secret.from_env_var("HF_API_TOKEN"),
)

pipe = Pipeline()
pipe.add_component("prompt_builder", prompt_builder)
pipe.add_component("llm", llm)
pipe.connect("prompt_builder.prompt", "llm.messages")
location = "Berlin"
messages = [
    ChatMessage.from_system(
        "Always respond in German even if some input data is in other languages.",
    ),
    ChatMessage.from_user("Tell me about {{location}}"),
]
pipe.run(
    data={
        "prompt_builder": {
            "template_variables": {"location": location},
            "template": messages,
        },
    },
)
```