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# Axolotl

[Axolotl](https://docs.axolotl.ai/) is a fine-tuning and post-training framework for large language models. It supports adapter-based tuning, ND-parallel distributed training, GRPO, and QAT. Through [TRL](./trl), Axolotl also handles preference learning, reinforcement learning, and reward modeling workflows.

Define your training run in a YAML config file.

```yaml
base_model: NousResearch/Nous-Hermes-llama-1b-v1
model_type: AutoModelForCausalLM
tokenizer_type: AutoTokenizer

datasets:
  - path: tatsu-lab/alpaca
    type: alpaca

output_dir: ./outputs
sequence_len: 512
micro_batch_size: 1
gradient_accumulation_steps: 1
num_epochs: 1
learning_rate: 2.0e-5
```

Launch training with the [train](https://docs.axolotl.ai/docs/cli.html#train) command.

```bash
axolotl train my_config.yml
```

## Transformers integration

Axolotl's [ModelLoader](https://docs.axolotl.ai/docs/api/loaders.model.html#axolotl.loaders.model.ModelLoader) wraps the Transformers load flow.

- The model config builds from [`AutoConfig.from_pretrained`]. Preload setup configures the [device map](https://huggingface.co/docs/accelerate/concept_guides/big_model_inference#designing-a-device-map), [quantization config](../main_classes/quantization), and [attention backend](../attention_interface).

- `ModelLoader` automatically selects the appropriate [`AutoModel`] class ([`AutoModelForCausalLM`], [`AutoModelForImageTextToText`], [`AutoModelForSequenceClassification`]) or a model-specific class from the multimodal mapping. Weights load with the selected loader's `from_pretrained`. When `reinit_weights` is set, Axolotl uses `from_config` for random initialization.

- Axolotl uses Transformers, [PEFT](https://huggingface.co/docs/peft/index), and [bitsandbytes](https://huggingface.co/docs/bitsandbytes/index) to apply adapters after model initialization when PEFT-based techniques such as LoRA and QLoRA are enabled. A patch manager applies additional optimizations before and after model loading.

- [AxolotlTrainer](https://docs.axolotl.ai/docs/api/core.trainers.base.html#axolotl.core.trainers.base.AxolotlTrainer) extends [`Trainer`], adding Axolotl mixins while using the [`Trainer`] training loop and APIs.

## Resources

- [Axolotl](https://docs.axolotl.ai/) docs
