Soft Sequence Policy Optimization

Svetlana Glazyrina, Maksim Kryzhanovskiy, Roman Ischenko


Abstract
A significant portion of recent research on Large Language Model (LLM) alignment focuses on developing new policy optimization methods based on Group Relative Policy Optimization (GRPO). Two prominent directions have emerged: (i) a shift toward sequence-level importance sampling weights that better align with the sequence-level rewards used in many tasks, and (ii) alternatives to the PPO-style clipping that aim to avoid the associated loss of training signal and entropy collapse. We introduce Soft Sequence Policy Optimization, an off-policy reinforcement learning objective that incorporates soft gating functions over token-level probability ratios within sequence-level importance weights. We provide theoretical motivation for SSPO and investigate practical modifications to improve optimization behavior. Empirically, we demonstrate that SSPO improves training stability and performance both in mathematical reasoning and coding tasks.
Anthology ID:
2026.findings-emnlp.2472
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:
53191–53201
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2472/
DOI:
10.18653/2026.findings-emnlp.2472
Bibkey:
Cite (ACL):
Svetlana Glazyrina, Maksim Kryzhanovskiy, and Roman Ischenko. 2026. Soft Sequence Policy Optimization. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 53191–53201, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Soft Sequence Policy Optimization (Glazyrina et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.2472.pdf