> For the complete documentation index, see [llms.txt](https://docs.aios.foundation/aios-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aios.foundation/aios-docs/aios-kernel/llm-cores/hugging-face-backend.md).

# Hugging Face Backend

The Hugging Face Local Backend allows running models locally using the Hugging Face Transformers library.

The HF Local Backend is initialized as a class instance:

```python
case "huggingface":
    self.llms.append(HfLocalBackend(
        model_name=config.name,
        max_gpu_memory=config.max_gpu_memory,
        eval_device=config.eval_device
    ))
```

It handles loading and running Hugging Face models locally, with options for GPU memory allocation.

**Standard Text Input**

For standard text requests, the backend uses the `generate()` method:

```python
completed_response = model.generate(**completion_kwargs)
return completed_response, True
```

**Tool Calls**

As huggingface models do not natively support tool calls, the adapter merges tool information into messages before generation and decodes tool calls after generation. 

```python
if tools:
    new_messages = merge_messages_with_tools(messages, tools)
    completion_kwargs["messages"] = new_messages

completed_response = model.generate(**completion_kwargs)

# During processing
if tools:
    if isinstance(model, HfLocalBackend):
        if finished:
            tool_calls = decode_hf_tool_calls(completed_response)
            tool_calls = double_underscore_to_slash(tool_calls)
            return LLMResponse(
                response_message=None,
                tool_calls=tool_calls,
                finished=finished
            )
```

The [`merge_messages_with_tools()`](https://github.com/agiresearch/AIOS/blob/main/aios/llm_core/utils.py) function formats the tool information into the prompt, and [`decode_hf_tool_calls()`](https://github.com/agiresearch/AIOS/blob/main/aios/llm_core/utils.py) extracts tool calls from the text response.

**JSON-Formatted Responses**

JSON formatting is handled by merging the response format into the messages:

```python
elif message_return_type == "json":
    new_messages = merge_messages_with_response_format(messages, response_format)
    completion_kwargs["messages"] = new_messages
```

The [`merge_messages_with_response_format()`](https://github.com/agiresearch/AIOS/blob/main/aios/llm_core/utils.py) function likely adds instructions for the model to respond in JSON format.


---

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