arXiv AI
Oct 1

Explicit Trajectory Diversity for RL-Based Post-Training of LLM Agents

The paper introduces Trajectory-guided Joint Policy Optimization (TJPO), a reinforcement‑learning framework that explicitly encourages diversity in the trajectories of large‑language‑model agents. By defining task‑specific trajectory descriptors, TJPO measures and optimizes diversity as a set‑level function, avoiding population‑based training. Experiments on Sokoban and ALFWorld demonstrate that TJPO yields diverse, interpretable behaviors while preserving strong task performance.

By Huaiyu Fu, Heng Cao, Hao Wang, Jian Ya, Tao Chen
arXiv AI
Oct 28

Repulsive Population Policy Gradients for Behaviorally Diverse Reinforcement Learning

The paper introduces RePPO, a method that adapts Proximal Policy Optimization to jointly optimize a compact population of diverse, high‑quality policies using a population‑dependent, dynamically shaped reward. RePPO achieves a strong quality‑diversity tradeoff on standard continuous‑control tasks and scales to larger policy and behavior spaces, maintaining quality while significantly increasing diversity in pixel‑based tasks. The authors also demonstrate RePPO’s applicability to fine‑tuning large language models, showing for the first time that quality‑diversity reinforcement learning can scale to this domain.

By Saeed Hedayatian, Harsh Shah, Celine Mneimneh, Stefanos Nikolaidis
arXiv Computation and Language
Oct 27

Evolving Language Models without Labels: Majority Drives Selection, Novelty Promotes Variation

arXiv:2509.15194v4 Announce Type: replace-cross Abstract: Large language models (LLMs) can improve through reinforcement learning with verifiable rewards (RLVR), but many settings lack reference answ...

By Yujun Zhou, Zhenwen Liang, Haolin Liu, Wenhao Yu, Kishan Panaganti, Linfeng Song, Dian Yu, Xiangliang Zhang, Haitao Mi, Dong Yu