Entropy-Aware Token Rejection for Improving Speculative Decoding

Tiancheng Su, Meicong Zhang, Guoxiu He


Abstract
Speculative decoding (SD) accelerates large language model (LLM) inference by using a lightweight draft model to propose tokens and a stronger target model to verify them. However, standard SD is mainly designed for acceleration, and its output quality is typically constrained by the target model. In this work, we propose Entropy-Aware Speculative Decoding (EASD), a lightweight and training-free extension of SD that improves reasoning quality through token-level entropy-guided rejection. EASD detects cases where both draft and target models exhibit high uncertainty while strongly overlapping in their top predictions. In such uncertain-agreement cases, EASD rejects the aligned token and resamples from the target distribution, preventing low-confidence errors from propagating. Experiments on challenging reasoning benchmarks show that EASD consistently improves accuracy over standard SD and reward-guided variants while maintaining comparable inference efficiency. Notably, EASD can surpass the standalone performance of the target model, suggesting that speculative decoding can serve not only as an acceleration method but also as an effective mechanism for improving reasoning quality. The code is available at https://github.com/ECNU-Text-Computing/EASD.
Anthology ID:
2026.findings-emnlp.278
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:
5847–5864
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.278/
DOI:
Bibkey:
Cite (ACL):
Tiancheng Su, Meicong Zhang, and Guoxiu He. 2026. Entropy-Aware Token Rejection for Improving Speculative Decoding. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 5847–5864, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Entropy-Aware Token Rejection for Improving Speculative Decoding (Su et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.278.pdf