Tower-7B-Sep_0c1t

This model is released as part of our paper Doc2FRC: Length-Consistent Document-Level Machine Translation via Fixed-Range Chunking. The code and paper-specific inference scripts are available in the Doc2FRC GitHub repository.

Tower-7B-Sep_0c1t is a full-parameter fine-tuned version of Unbabel/TowerInstruct-Mistral-7B-v0.2 for multilingual chunk-level machine translation. It is the Sep_0c1t variant: each call translates one source chunk into one target chunk without preceding context chunks. The training examples were derived from sardinelab/DocBlocks using fixed-range chunking.

Supported translation directions

The model supports translation between English and the following languages in both directions:

• German
• Spanish
• French
• Italian
• Korean
• Dutch
• Portuguese
• Russian
• Chinese

General usage

The example below demonstrates general model usage for translating a single chunk. For the exact document chunking, inference scripts, prompting setup, and evaluation procedure used in the paper, please refer to the Doc2FRC GitHub repository.

Recommended prompt format

The model was fine-tuned with the following raw ChatML-style translation prompt:

<|im_start|>user
Translate the following source text from {SOURCE_LANGUAGE} into {TARGET_LANGUAGE}.
{SOURCE_LANGUAGE}: {SOURCE_TEXT}.
{TARGET_LANGUAGE}: <|im_end|>
<|im_start|>assistant

Use full English language names such as English, Chinese, German, or Russian. The model was trained on source and target chunks in the 256–512 token range.

Transformers example

Install a PyTorch build appropriate for your hardware, together with Transformers and Accelerate. PyTorch 2.6 or later is recommended for loading the current PyTorch .bin checkpoint files.

pip install "transformers>=4.56.2" accelerate

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

MODEL_ID = "ynklab/Tower-7B-Sep_0c1t"

tokenizer = AutoTokenizer.from_pretrained(MODEL_ID)
model = AutoModelForCausalLM.from_pretrained(
    MODEL_ID,
    dtype=torch.bfloat16,
    device_map="auto",
)
model.eval()

source_language = "English"
target_language = "Chinese"
source_text = "The weather is nice today"

prompt = (
    "<|im_start|>user\n"
    f"Translate the following source text from {source_language} "
    f"into {target_language}.\n"
    f"{source_language}: {source_text}.\n"
    f"{target_language}: <|im_end|>\n"
    "<|im_start|>assistant\n"
)

# The Tower tokenizer adds the beginning-of-sequence token used during training.
inputs = tokenizer(prompt, return_tensors="pt")
inputs = {name: tensor.to(model.device) for name, tensor in inputs.items()}

with torch.inference_mode():
    outputs = model.generate(
        **inputs,
        max_new_tokens=1024,
        do_sample=False,
        repetition_penalty=1.05,
    )

generated_tokens = outputs[0, inputs["input_ids"].shape[1]:]
translation = tokenizer.decode(
    generated_tokens,
    skip_special_tokens=True,
).strip()

print(translation)

For paper-level document translation, split the document into fixed-range chunks and reconstruct the translated chunks using the procedures provided in the Doc2FRC repository.

Training

• Base model: TowerInstruct-Mistral-7B-v0.2
• Training method: full-parameter supervised fine-tuning
• Training variant: Sep_0c1t (zero preceding context chunks and one target chunk)
• Chunk range: 256–512 tokens
• Epochs: 2
• Learning rate: 7e-6
• Learning-rate scheduler: cosine
• Warmup steps: 125
• Maximum sequence length: 32,768 tokens
• Training precision: bfloat16
• Optimizer: AdamW
• Weight decay: 0.01

License

This model preserves the CC BY-NC-SA 4.0 License distributed with its base model, TowerInstruct-Mistral-7B-v0.2. See the LICENSE file and the upstream model card for the applicable terms.

DocBlocks contains material derived from multiple sources. Users should also consult the DocBlocks dataset and the original data sources for their applicable licensing conditions.

Acknowledgements

This model is based on TowerInstruct-Mistral-7B-v0.2 and was fine-tuned using DocBlocks. Please cite our paper when using this model in academic work.

Citation

@misc{wang2026doc2frclengthconsistentdocumentlevelmachine,
      title={Doc2FRC: Length-Consistent Document-Level Machine Translation via Fixed-Range Chunking}, 
      author={Xiaotian Wang and Youyuan Lin and Zhan Shen and Hitomi Yanaka},
      year={2026},
      eprint={2609.12674},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2609.12674}, 
}