AT-TTA: Dual-View Anchor-Tethered Test-Time Adaptation for Large Language Models

Yaxin Wang, Junfeng He, Zhihui Lu, Weishen Lu, Shijing Hu, Peng Chen, Ye Wang, Chao Huang, Yao Cheng, Yudong Cheng


Abstract
Large Language Models (LLMs) frequently exhibit performance degradation in specialized domains due to distribution shifts. While unsupervised Test-Time Adaptation (TTA) offers a lightweight solution, existing methods suffer from critical flaws: input-centric adaptation lacks reasoning constraints, while output-centric optimization falls into a "Confidence Trap" of reinforced hallucinations. We instead study Few-Shot Anchored TTA, where a small labeled support set is available, and propose Anchor-Tethered Test-Time Adaptation (AT-TTA), a framework that synergizes linguistic alignment with reliable reasoning. AT-TTA employs Dual-View Uncertainty Calibration, minimizing input perplexity for domain alignment and sequence-level output energy for generation consistency. Furthermore, to mitigate catastrophic drift, we construct a "Semantic Anchor" by fine-tuning on the labeled support set and its filtered augmentations, which serves as a stable domain prior and constrains the adaptation trajectory via an Energy-Guided Adaptive Replay strategy. Extensive experiments on the AdaptEval benchmark demonstrate strong performance across diverse domains, effectively preventing model collapse while maintaining high inference efficiency.
Anthology ID:
2026.emnlp-main.1374
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:
31353–31381
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1374/
DOI:
Bibkey:
Cite (ACL):
Yaxin Wang, Junfeng He, Zhihui Lu, Weishen Lu, Shijing Hu, Peng Chen, Ye Wang, Chao Huang, Yao Cheng, and Yudong Cheng. 2026. AT-TTA: Dual-View Anchor-Tethered Test-Time Adaptation for Large Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 31353–31381, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
AT-TTA: Dual-View Anchor-Tethered Test-Time Adaptation for Large Language Models (Wang et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1374.pdf