BabySteps at BabyLM 2026: Stronger Optimization and Causal Baselines for Data-Constrained Pretraining

Siddhi Satheesh, Jorge C Murillo, Yubei Chen


Abstract
We present three BabySteps systems that strengthen baselines for data-constrained pretraining in the strict-small (10M words) and strict (100M words) NLP tracks of the 2026 BabyLM Challenge. Across our GPT-BERT experiments, optimizer choice and learning-rate tuning produced our largest gains, highlighting the importance of well-tuned baselines for evaluating progress in sample-efficient pretraining. The curriculum, synthetic-data, teacher-supervision, and corpus-mixing interventions that we tested did not improve the final aggregate score.

We also test whether the official GPT-2 checkpoint is a sufficiently strong reference for causal language modeling. A 127.6M-parameter Llama-style decoder trained with Muon and Liger-optimized kernels obtains a seven-suite NLP average of 56.18, compared with 52.79 for our completed reevaluation of the official BabyLM GPT-2 strict checkpoint, and scores higher on all seven categories. This is not a controlled architectural ablation: architecture, optimizer, implementation, and hyperparameters change together. Instead, it provides a stronger practical causal baseline. In addition, we report failed data interventions, a numerical failure caused by batches with no supervised target tokens, and substantial variance between small evaluation suites.
Anthology ID:
2026.babylm-main.63
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:
823–830
Language:
URL:
https://aclanthology.org/2026.babylm-main.63/
DOI:
Bibkey:
Cite (ACL):
Siddhi Satheesh, Jorge C Murillo, and Yubei Chen. 2026. BabySteps at BabyLM 2026: Stronger Optimization and Causal Baselines for Data-Constrained Pretraining. In Proceedings of the Second BabyLM Workshop, pages 823–830, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
BabySteps at BabyLM 2026: Stronger Optimization and Causal Baselines for Data-Constrained Pretraining (Satheesh et al., BabyLM 2026)
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PDF:
https://aclanthology.org/2026.babylm-main.63.pdf