Learning How to Align: Elastic Domain Adaptation for Improving Reasoning Robustness of Large Language Models

Yujie Hou, Mei Wang, Yaoyao Zhong, Guozhang Li, Qiannan Zhu, Hua Huang


Abstract
Despite exceptional performance on static benchmarks, Large Language Models (LLMs) exhibit significant brittleness when evaluated on perturbed variants of the original questions. Current extrinsic interventions, prompt engineering or supervised fine-tuning, overlook an important intrinsic factor underlying this degradation: the distributional shifts in layer activations between original and perturbed questions. To address this, this work formulates the reasoning robustness challenge as an Unsupervised Domain Adaptation (UDA) problem and proposes the Elastic Domain Adaptation (EDA) method. Unlike rigid strategies that enforce a uniform alignment constraint, EDA dynamically aligns layer activations based on the specific layers and perturbation types. Specifically, EDA incorporates an Adaptive Layer Selection (ALS) to identify pivotal layers and employs an Elastic Shift Module (ESM) to selectively pull or push layer representations depending on the perturbation types. Extensive experiments across six LLMs and 15 perturbation types demonstrate that EDA achieves state-of-the-art performance on most perturbed benchmarks while preserving reasoning capability on original benchmarks.
Anthology ID:
2026.emnlp-main.392
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
8995–9018
Language:
URL:
https://aclanthology.org/2026.emnlp-main.392/
DOI:
Bibkey:
Cite (ACL):
Yujie Hou, Mei Wang, Yaoyao Zhong, Guozhang Li, Qiannan Zhu, and Hua Huang. 2026. Learning How to Align: Elastic Domain Adaptation for Improving Reasoning Robustness of Large Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 8995–9018, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Learning How to Align: Elastic Domain Adaptation for Improving Reasoning Robustness of Large Language Models (Hou et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.392.pdf