BayLing-MLingual: One Model, 50 Languages, 2500 Cross-lingual Pairs

Mengyu Bu, Yang Feng

BayLing-MLingual is a multilingual question-answering model that supports 50 languages and 2500 cross-lingual pairs. Built on top of XBridge, BayLing-MLingual leverages a compositional Encoder-LLM-Decoder architecture that separates language understanding, knowledge & reasoning, and Language generation. This design enables strong multilingual performance across both high-resource and low-resource languages while preserving the reasoning capabilities of the base LLM.

🚀Key Features

• 50 languages and 2500 cross-lingual pairs: A single model supports 50 languages across diverse language families. Input and output languages can be selected independently.
• Strong multilingual performance: BayLing-MLingual preserves the reasoning and knowledge capabilities of the underlying LLM while extending multilingual understanding and generation.
• Low-resource & unseen language transfer: BayLing-MLingual demonstrates strong performance on high-resource languages, low-resource languages and previously unseen languages, without retraining the LLM.
• Efficient Deployment: Only lightweight multilingual modules are added on top of the LLM.

💬 Example Interactions

Japanese → Swahili

Question

地球は丸いですか？

Answer

Ndiyo. Dunia ni mviringo.

Arabic → Chinese

Question

أين تقع عاصمة الصين؟

Answer

中国的首都是北京。

Bengali → German

Question

সূর্য কেন উজ্জ্বল?

Answer

Die Sonne leuchtet aufgrund der Kernfusion im Sonnenkern.

🌐Supported Languages

Code	Language
en	English
zh	Chinese
ja	Japanese
de	German
fr	French
es	Spanish
ru	Russian
sw	Swahili
bn	Bengali
th	Thai
af	Afrikaans
ar	Arabic
az	Azerbaijani
cs	Czech
el	Greek
et	Estonian
fa	Persian
fi	Finnish
gl	Galician
gu	Gujarati
he	Hebrew
hi	Hindi
hr	Croatian
id	Indonesian
it	Italian
ka	Georgian
kk	Kazakh
km	Khmer
lt	Lithuanian
lv	Latvian
mk	Macedonian
ml	Malayalam
mn	Mongolian
mr	Marathi
my	Burmese
ne	Nepali
nl	Dutch
pl	Polish
ps	Pashto
pt	Portuguese
ro	Romanian
sl	Slovenian
sv	Swedish
ta	Tamil
te	Telugu
tr	Turkish
uk	Ukrainian
ur	Urdu
vi	Vietnamese
xh	Xhosa

📄Model Details

Item	Value
Base LLM	LLaMA3-8B
Framework	XBridge
Architecture	Encoder-LLM-Decoder
Languages	50
Cross-lingual Pairs	2500
Multilingual Encoder	NLLB Encoder
Multilingual Decoder	NLLB Decoder

🔬Technical Report

BayLing is built upon XBridge. For architecture details, training methodology, and experimental analysis, see XBridge repository and ACL 2026 paper.

⚖️LICENSE

Our code is released under the Apache-2.0 License. Our model is intended for academic research purposes only and may NOT be used for commercial purposes.

You are free to use, modify, and distribute this model in academic settings, provided that the following conditions are met:

• Non-commercial use: The model may not be used for any commercial purposes.
• Citation: If you use this model in your research, please cite the original work.

❗Commercial Use Restriction

For any commercial use inquiries or to obtain a commercial license, please contact fengyang@ict.ac.cn.

📚Citation

If you have any questions, please feel free to submit an issue or contact bumengyu23z@ict.ac.cn.

If you find this repository useful, please star this repository and cite our paper:

@misc{bu2026languagedemandknowledgecore,
      title={Language on Demand, Knowledge at Core: Composing LLMs with Encoder-Decoder Translation Models for Extensible Multilinguality}, 
      author={Mengyu Bu and Yang Feng},
      year={2026},
      eprint={2603.17512},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2603.17512}, 
}