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axolotl/docs/1_58bit_finetuning.qmd
Younes B e662972a29 Feat: Add bitnet integration (#3634)
* add bitnet

* switch to uv

* chore: liint

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Co-authored-by: Wing Lian <wing@axolotl.ai>
2026-04-30 11:25:02 -04:00

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---
title: "1.58-bit Finetuning"
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toc-depth: 4
---
## Overview
1.58-bit finetuning allows you to finetune BitNet models when their prequantized weights are provided. In theory, it will be possible to fine-tune any LLM in 1.58bit format but the performance degradation will be dramatic.
Axolotl supports 1.58-bit finetuning via the [`onebitllms`](https://github.com/tiiuae/onebitllms) library, which replaces standard linear layers with BitNet-compatible counterparts ready to use for training.
::: {.callout-note}
LoRA is not supported for BitNet models
:::
## Installation
Install the `onebitllms` package before using this feature:
```bash
uv pip install onebitllms
```
Or from source:
```bash
uv pip install git+https://github.com/tiiuae/onebitllms
```
## Supported models
For now, only `Falcon-E` series of models are supported. Make sure to use their `-prequantized` version:
```bash
tiiuae/Falcon-E-3B-Base-prequantized
tiiuae/Falcon-E-1B-Base-prequantized
```
In theory, any other model would 'work' but the performance degradation will be huge. This remains an area of exploration.
## Configuration
To enable 1.58-bit finetuning, set the following in your configuration file:
```yaml
base_model: tiiuae/Falcon-E-3B-Base-prequantized # A BitNet-compatible model
use_onebitllms: true
```
::: {.callout-note}
For BitNet models, it is recommended to use a higher learning rate than classic models (usually in the order of magnitude of 10x).
:::
## Considerations after training
Once your model has been trained with 1.58bit fine-tuning, you can convert the trained model in ternary format using the `onebitllms` CLI:
```bash
onebitllms quantize_to_1bit INPUT_PATH OUTPUT_PATH
```
After that, you can use supported packages such as `llama.cpp` or Apple MLX package to run the trained model.
## Example Configuration
You can find example configurations in `examples/falcon-e` which contain one configuration for SFT and one configuration for DPO.