Trust Your Guide Only When Certain: Uncertainty-Aware Sparse Alignment at Inference Time

Zeen Zhu, Zhuo Li, Weiyang Guo, Liye Zhao, Haibing Di, Yequan Wang, Jing Li


Abstract
A prominent paradigm in inference-time alignment employs lightweight supervisors to steer Large Language Models (LLMs). Through empirical analysis, we identify a structural mismatch in this paradigm: weak supervisors exhibit pervasive high entropy across the vast majority of tokens, yet prevailing dense intervention approaches mandate supervision at every decoding step. This leads to frequent low-confidence interventions that can disrupt valid base-model reasoning and incur substantial utility costs. To resolve this, we propose TUSA (Trust-based Uncertainty Sparse Alignment). Moving away from continuous oversight, TUSA reframes alignment as a dynamic arbitration process, introducing an uncertainty-aware arbiter that authorizes intervention only when two conditions are met: the supervisor is confident and the token is semantically salient. This mechanism effectively filters out uncertainty-driven noise and redundant supervision. Extensive experiments across multiple models and benchmarks show that TUSA consistently improves both safety alignment and general helpfulness. By bypassing approximately 50% of alignment steps, it not only enhances safety preference by up to 15.6%, but also boosts general preference rates by up to 12.0% compared to the dense baseline, demonstrating that selective, high-precision alignment can outperform continuous supervision.
Anthology ID:
2026.findings-emnlp.391
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
8237–8263
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URL:
https://aclanthology.org/2026.findings-emnlp.391/
DOI:
Bibkey:
Cite (ACL):
Zeen Zhu, Zhuo Li, Weiyang Guo, Liye Zhao, Haibing Di, Yequan Wang, and Jing Li. 2026. Trust Your Guide Only When Certain: Uncertainty-Aware Sparse Alignment at Inference Time. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 8237–8263, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Trust Your Guide Only When Certain: Uncertainty-Aware Sparse Alignment at Inference Time (Zhu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.391.pdf