Compact Multilingual Pre-training under the BabyLM 100M-Word Budget with Regex-Guided Tokenization and Attention Residuals

Yihan Liu, Tongjing Zhang, Pierre Nugues


Abstract
Multilingual pre-training under severe data con straints can suffer from limited representational capacity and uneven tokenization across lan guages. Addressing the BabyLM 2026 Multi lingual Track, we study a compact pre-training recipe under the 100M-word budget. Our main contribution is a Calibrated Regex-Guided Byte-Level BPE (Regex-BBPE) tokenizer that combines script-aware pre-tokenization with byte-premium-adjusted tokenizer training in a 16K vocabulary. We pair this tokenizer with the previously proposed Attention Residuals mechanism and the Muon optimizer, and eval uate three English/Dutch/Chinese mixing ra tios. Among the tested mixtures, the Chinese dominant configuration (20% English, 20% Dutch, 60% Chinese) gives the strongest ag gregate fine-tuning results. Zero-shot results are mixed and remain slightly below the offi cial GPT-2 trilingual baseline on average, while fine-tuning improves the language-level aver ages by 8.55, 9.55, and 10.09 accuracy points for English, Dutch, and Chinese, respectively. The mixing-ratio experiments also show differ ent sensitivity patterns for the two West Ger manic languages and Chinese; we treat this as an observation within the tested language triple rather than a general cross-lingual law.
Anthology ID:
2026.babylm-main.32
Volume:
Proceedings of the Second BabyLM Workshop
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Leshem Choshen, Ryan Cotterell, Mustafa Omer Gul, Jaap Jumelet, Tal Linzen, Aaron Mueller, Suchir Salhan, Raj Sanjay Shah, Alex Warstadt, Ethan Gotlieb Wilcox
Venues:
BabyLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
403–412
Language:
URL:
https://aclanthology.org/2026.babylm-main.32/
DOI:
Bibkey:
Cite (ACL):
Yihan Liu, Tongjing Zhang, and Pierre Nugues. 2026. Compact Multilingual Pre-training under the BabyLM 100M-Word Budget with Regex-Guided Tokenization and Attention Residuals. In Proceedings of the Second BabyLM Workshop, pages 403–412, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Compact Multilingual Pre-training under the BabyLM 100M-Word Budget with Regex-Guided Tokenization and Attention Residuals (Liu et al., BabyLM 2026)
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PDF:
https://aclanthology.org/2026.babylm-main.32.pdf