Markhor: A framework for Adapting LLMs to Urdu via Alignment-Free Tokenizer Replacement

Muhammad Zain Ali, Yuxia Wang, Muhammad Arslan Manzoor, Tony C Smith, Bernhard Pfahringer


Abstract
Large language models (LLMs) have established state-of-the-art performance across many NLP tasks, yet their effectiveness for low-resource languages such as Urdu remains limited due to under-representation in pretraining corpora and inadequate tokenization. This study explores adapting pretrained LLMs to new languages by replacing the original tokenizer without cross-lingual correspondence. We show that stable adaptation depends on maintaining architectural compatibility, matching vocabulary size, and reusing pretrained embedding and language modeling head weights. We propose *Markhor*, a framework for adapting LLMs to low-resource languages in this way. It spans tokenizer training, continual pretraining, and instruction tuning via knowledge distillation, resulting in two models, *MKGPT* and *MKQwen*, based on GPT and Qwen architectures. These models are evaluated on multiple classification tasks (fake news detection, hate speech detection, emotion classification) and open-ended question answering. Results show both MKGPT and MKQwen outperform baselines across all tasks, suggesting the effectiveness of the methodology for developing open-source Urdu LLMs.
Anthology ID:
2026.findings-aacl.114
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
2260–2272
Language:
URL:
https://aclanthology.org/2026.findings-aacl.114/
DOI:
Bibkey:
Cite (ACL):
Muhammad Zain Ali, Yuxia Wang, Muhammad Arslan Manzoor, Tony C Smith, and Bernhard Pfahringer. 2026. Markhor: A framework for Adapting LLMs to Urdu via Alignment-Free Tokenizer Replacement. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 2260–2272, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Markhor: A framework for Adapting LLMs to Urdu via Alignment-Free Tokenizer Replacement (Ali et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.114.pdf