[Submitted on 29 Jun 2026]
Title:When Does Learning to Stop Help? A Cost-Aware Study of Early Exits in Reasoning Models
View a PDF of the paper titled When Does Learning to Stop Help? A Cost-Aware Study of Early Exits in Reasoning Models, by Zhe Dong (University of Maine at Presque Isle) and 2 other authors
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Abstract:Reasoning models spend different amounts of useful computation across instances, but it remains unclear when a learned stopping rule improves over simple confidence or convergence thresholds. We study this question with LearnStop, a hidden-state-free checkpoint stopper for reasoning language models. At fixed budget checkpoints, LearnStop probes a short answer from the current reasoning prefix and predicts prefix correctness from online features such as answer confidence, entropy, prefix vote share, answer stability, and backtracking-marker density. Across 18 task-model settings spanning GSM8K, MATH-500, MMLU-Pro, AIME-90, GPQA, Qwen3, and DeepSeek-R1 distillations, the answer is task-dependent. On free-form math, learned multi-feature stopping improves the fixed-budget frontier and often beats scalar exits: on GSM8K with Qwen3-32B, the empirical frontier reaches a post-hoc peak adapt gain of +0.157, validation-selected operating points preserve positive gains, and the paired gain over the strongest scalar baseline is +0.028. On multiple-choice and very hard settings, scalar confidence, entropy, or stability rules are competitive or stronger. We therefore frame learned stopping not as a universal replacement for scalar exits, but as a tool whose value depends on trajectory structure. We further provide validation-selected operating points, paired bootstrap tests, finite-grid lost-correct risk calibration, cost accounting under KV-fork, prefix-cache, and black-box regimes, H100 serving profiles, checkpoint-schedule sweeps, transfer analyses, and robustness checks. The main practical finding is that learned stopping is useful when many questions become correct before full budget but do not exhibit a single reliable scalar stopping signal; its benefits largely disappear when confidence or answer convergence already solves the stopping problem.
Comments: 17 pages, 5 figures
Subjects:
Artificial Intelligence (cs.AI); Computation and Language (cs.CL); Machine Learning (cs.LG)
ACM classes: I.2.6; I.2.7
Cite as: arXiv:2606.30852 [cs.AI]
(or arXiv:2606.30852v1 [cs.AI] for this version)
https://doi.org/10.48550/arXiv.2606.30852
arXiv-issued DOI via DataCite (pending registration)
Submission history
From: Zhe Dong [view email] [v1] Mon, 29 Jun 2026 19:33:42 UTC (88 KB)
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