arXiv AI

Selective Successor Eligibility Traces for RLVR

The paper introduces Selective Successor Eligibility Traces (S-trace), a critic‑free eligibility trace method designed to improve temporal credit assignment in Reinforcement Learning with Verifiable Rewards (RLVR). S-trace reweights successor importance to recover downstream credit signals under PPO-style clipping and selectively propagates them to historical tokens using entropy-based token selection. Experiments on Qwen3 models show that S-trace yields significant absolute gains in average pass@16 over GRPO and trace-style GRPO, while also producing shorter responses.

arXiv AI
Sep 15

HISPO: Hierarchical Importance-Sampling Policy Optimization with Entropy-Derived Segments

HISPO introduces a segment‑level policy‑optimization technique for reinforcement learning with verifiable rewards, creating entropy‑derived contiguous segments during rollout and applying clipped importance‑sampling correction at this granularity. It bridges the gap between token‑level and sequence‑level corrections, offering a middle‑ground approach for credit assignment in long‑form mathematical reasoning. Evaluated on Qwen3‑1.7B‑Base across six benchmarks, HISPO consistently outperforms or matches the strongest baselines in Pass@8 and Acc@8 metrics, notably improving AIME25 scores over GRPO and GSPO.

By Quoc-Vinh Lai-Dang, Hyo-Sang Shin
arXiv AI
Sep 30

Targeting Pivotal Decisions for Credit Assignment in Agentic Reinforcement Learning

arXiv:2609.36178v1 Announce Type: cross Abstract: Group Relative Policy Optimization (GRPO) has become a promising approach for training large language model agents. However, its uniform assignment o...

By Dongwon Jung, Hemanth Neelgund Ramesh, Yifan Wang, Xiaomin Li, Yuexing Hao, Yu Hu, Muhao Chen, Varun Chandrasekaran, Andrzej Banburski-Fahey, Jaron Lanier
arXiv AI
Oct 1

Advancing Entropy-Level Credit Assignment in RLVR via Proximal Entropy Policy Optimization

The paper introduces Proximal Entropy Policy Optimization (PEPO), a method that assigns token‑level advantages in reinforcement learning for language models based on a local measure of entropy called proximal entropy. Unlike prior approaches that use global token entropy, PEPO evaluates importance relative to neighboring tokens, making it invariant to prompt difficulty and positional effects. Experiments on Qwen3 and Llama‑3.2 models show PEPO outperforms GRPO and other entropy‑based baselines in mathematical reasoning tasks.

By Yun Kim, Nojun Kwak