STARS: State-Aware Reasoning Stopping via Hidden-State Spectral Analysis

Aaron T. Cheng, Junda Wu, Sheldon Yu, Rui Wang, Ryan A. Rossi, Sizhe Zhou, Jiawei Han, Julian McAuley, Lina Yao, Tong Yu


Abstract
Chain-of-thought (CoT) reasoning in large language models often produces redundant steps that increase generation cost and obscure when reasoning has effectively completed. Existing stopping methods rely on output-level or token-level signals, overlooking internal representation dynamics that reflect reasoning progress. We propose STARS (STate-Aware Reasoning Stopping), a framework that leverages spectral analysis of hidden-state representations to detect transitions in reasoning phases. Our key insight is that structural changes in the representation space capture shifts in reasoning states, enabling early and reliable stopping decisions. To address representation instability, where semantically similar steps can induce different hidden states, we focus on spectral structure rather than raw activations, improving robustness to context-dependent drift. Experiments on four mathematical and logical reasoning benchmarks show that STARS reduces generation cost by over 45% under fixed token budgets while improving accuracy over standard CoT baselines.
Anthology ID:
2026.findings-emnlp.1790
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:
38289–38306
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URL:
https://aclanthology.org/2026.findings-emnlp.1790/
DOI:
Bibkey:
Cite (ACL):
Aaron T. Cheng, Junda Wu, Sheldon Yu, Rui Wang, Ryan A. Rossi, Sizhe Zhou, Jiawei Han, Julian McAuley, Lina Yao, and Tong Yu. 2026. STARS: State-Aware Reasoning Stopping via Hidden-State Spectral Analysis. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 38289–38306, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
STARS: State-Aware Reasoning Stopping via Hidden-State Spectral Analysis (Cheng et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1790.pdf