LADA: Enabling Adaptation of Black-Box LLMs to Dynamic Domain Changes at Test Time

Yihao Hu, Congyu Qiao, Junming Yang, Mofei Song, Xin Geng, Ning Xu


Abstract
Adaptation of black-box large language models (LLMs) at test time seeks to adjust LLMs to target domains in order to handle distribution shifts during testing, without access to model parameters. Most existing approaches rely on adapters trained with substantial target-domain data, which is often scarce in practical scenarios, and these adapters are tightly coupled to their training distribution, leading to degraded performance in dynamic scenarios with changing domains. To solve this, we propose LADA, a framework leveraging meta-training for continuous and rapid adaptation of black-box LLMs to unseen and changing domains. Specifically, LADA meta-trains an adapter on diverse tasks that cover multiple datasets and error combinations to learn transferable adaptation skills. At test time, the adapter needs only a few target-domain examples for lightweight adaptation and guides the LLM stepwise toward domain-appropriate reasoning via adaptive selection of reliable steps, without any updates to the LLM parameters. Experiments on datasets spanning multiple domains validate the effectiveness of the proposed approach.
Anthology ID:
2026.emnlp-main.1190
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:
27274–27291
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1190/
DOI:
Bibkey:
Cite (ACL):
Yihao Hu, Congyu Qiao, Junming Yang, Mofei Song, Xin Geng, and Ning Xu. 2026. LADA: Enabling Adaptation of Black-Box LLMs to Dynamic Domain Changes at Test Time. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 27274–27291, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
LADA: Enabling Adaptation of Black-Box LLMs to Dynamic Domain Changes at Test Time (Hu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1190.pdf