---
title: "LiteLLMChatGenerator"
id: litellmchatgenerator
slug: "/litellmchatgenerator"
description: "Enables chat completion using any of 100+ LLM providers through LiteLLM."
---

# LiteLLMChatGenerator

This component enables chat completion using various LLM providers through [LiteLLM](https://docs.litellm.ai/).

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

|  |  |
| --- | --- |
| **Most common position in a pipeline** | After a [ChatPromptBuilder](../builders/chatpromptbuilder.mdx) |
| **Mandatory init variables** | None. The provider's API key is read by LiteLLM from its standard environment variable (for example, `OPENAI_API_KEY` or `ANTHROPIC_API_KEY`). You can also pass it explicitly through the `api_key` init parameter. |
| **Mandatory run variables** | `messages`: A list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx) objects |
| **Output variables** | `replies`: A list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx) objects |
| **API reference** | [LiteLLM](/reference/integrations-litellm) |
| **GitHub link** | https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/litellm |
| **Package name** | `litellm-haystack` |

</div>

## Overview

`LiteLLMChatGenerator` routes chat completions through [LiteLLM](https://docs.litellm.ai/), which exposes a single, unified interface to over 100 LLM providers, including OpenAI, Anthropic, Google, AWS Bedrock, Azure, Cohere, Mistral, and Groq. This lets you switch providers by changing only the `model` string, without rewriting your pipeline.

### Parameters

Model names use the LiteLLM `provider/model-name` format, for example `openai/gpt-4o`, `anthropic/claude-sonnet-4-20250514`, or `bedrock/anthropic.claude-3-5-sonnet-20241022-v2:0`. The default model is `openai/gpt-4o`. See the [LiteLLM providers documentation](https://docs.litellm.ai/docs/providers) for the full list of supported providers and their model identifiers.

`LiteLLMChatGenerator` needs an API key for the selected provider. You can provide it in two ways:

- Let LiteLLM resolve credentials itself from the provider's standard environment variable, such as `OPENAI_API_KEY` or `ANTHROPIC_API_KEY` (recommended).
- Pass it explicitly through the `api_key` init parameter and Haystack's [Secret](../../concepts/secret-management.mdx) API: `Secret.from_env_var("OPENAI_API_KEY")`. Use this only when you want Haystack to manage and serialize the key.

If you run against a self-hosted LiteLLM proxy or a custom endpoint, set the `api_base_url` parameter.

You can pass any parameter supported by [`litellm.completion()`](https://docs.litellm.ai/docs/completion/input) through the `generation_kwargs` parameter, both at initialization and when running the component. LiteLLM normalizes these parameters across providers and drops the ones a given provider does not support.

Finally, the component needs a list of `ChatMessage` objects to operate. `ChatMessage` is a data class that contains a message, a role (who generated the message, such as `user`, `assistant`, `system`, `function`), and optional metadata.

### Tool Support

`LiteLLMChatGenerator` supports function calling through the `tools` parameter, which accepts flexible tool configurations:

- **A list of Tool objects**: Pass individual tools as a list
- **A single Toolset**: Pass an entire Toolset directly
- **Mixed Tools and Toolsets**: Combine multiple Toolsets with standalone tools in a single list

Tool calls work with both the synchronous and streaming responses, as long as the underlying provider and model support function calling. For more details on working with tools, see the [Tool](../../tools/tool.mdx) and [Toolset](../../tools/toolset.mdx) documentation.

### Streaming

You can stream output as it's generated. Pass a callback to `streaming_callback`. Use the built-in `print_streaming_chunk` to print text tokens and tool events (tool calls and tool results).

```python
from haystack.components.generators.utils import print_streaming_chunk
from haystack.dataclasses import ChatMessage
from haystack_integrations.components.generators.litellm import LiteLLMChatGenerator

generator = LiteLLMChatGenerator(
    model="openai/gpt-4o",
    streaming_callback=print_streaming_chunk,
)
generator.run([ChatMessage.from_user("Your question here")])
```

See our [Streaming Support](guides-to-generators/choosing-the-right-generator.mdx#streaming-support) docs to learn more how `StreamingChunk` works and how to write a custom callback.

### Asynchronous Execution

`LiteLLMChatGenerator` provides a `run_async` method for use in asynchronous pipelines and applications. It accepts the same parameters as `run` and supports both regular and streaming responses (pass an async streaming callback when streaming).

## Usage

Install the `litellm-haystack` package to use the `LiteLLMChatGenerator`:

```shell
pip install litellm-haystack
```

### On its own

```python
from haystack_integrations.components.generators.litellm import LiteLLMChatGenerator
from haystack.dataclasses import ChatMessage

generator = LiteLLMChatGenerator(
    model="anthropic/claude-sonnet-4-20250514",
    generation_kwargs={"max_tokens": 1024, "temperature": 0.7},
)

messages = [
    ChatMessage.from_system("You are a helpful assistant"),
    ChatMessage.from_user("What's Natural Language Processing? Be brief."),
]
result = generator.run(messages=messages)
print(result["replies"][0].text)
```

### In a pipeline

You can also use `LiteLLMChatGenerator` in a pipeline together with a `ChatPromptBuilder`.

```python
from haystack import Pipeline
from haystack.components.builders import ChatPromptBuilder
from haystack.dataclasses import ChatMessage
from haystack_integrations.components.generators.litellm import LiteLLMChatGenerator

pipe = Pipeline()
pipe.add_component("prompt_builder", ChatPromptBuilder())
pipe.add_component("llm", LiteLLMChatGenerator(model="openai/gpt-4o"))
pipe.connect("prompt_builder", "llm")

country = "Germany"
system_message = ChatMessage.from_system(
    "You are an assistant giving out valuable information to language learners.",
)
messages = [
    system_message,
    ChatMessage.from_user("What's the official language of {{ country }}?"),
]

res = pipe.run(
    data={
        "prompt_builder": {
            "template_variables": {"country": country},
            "template": messages,
        },
    },
)
print(res)
```