Reinforcement learning

Policy optimisation, reward modelling and RLHF — how models are trained by feedback rather than by labels.

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arXiv Machine Learning
Oct 8

EvoSignal: LLM-Guided Evolutionary Design of Modular Traffic Signal Control Programs

EvoSignal is an LLM‑guided evolutionary framework that treats traffic signal control as a modular program design problem, separating traffic feature extraction, local phase prioritization, and optional network‑based priority adjustment. Starting from established strategies, it iteratively improves programs using congestion and signal operation feedback, ultimately producing control rules that operate without online LLM inference. In simulations on two real‑world road networks, the best EvoSignal program reduced waiting time by 16.8–49.2% compared to 20 conventional, reinforcement‑learning, and LLM‑based baselines, and a travel‑time/queue‑length prioritizing program consistently outperformed all baselines across multiple scenarios.

By Leizhen Wang, Peibo Duan, Zhenlin Qin, Yancheng Ling, Jian Xu, Yue Wang, Hao Wang, Zhenliang Ma
arXiv Machine Learning
Oct 8

COPC: Coupled Off-Policy Correction for Asynchronous LLM Reinforcement Learning

The paper introduces COPC, a Coupled Off-Policy Correction method for asynchronous reinforcement learning of large language models. COPC coordinates policy-side and advantage-side corrections by combining token-level ratio masking with two-sided clipped-ratio weighting of TD residuals, addressing both policy mismatch and advantage staleness. Experiments show COPC outperforms existing asynchronous baselines on tool-integrated mathematical reasoning and search tasks, while maintaining training stability and minimal overhead.

By Zicheng Hu, Zhijian Zhou, Xuan Zhang, Yuchen Liu, Cheng Chen, Yuan Li, Qi Gu, Yan Feng, Hongyan Hao, Chao Qu
arXiv Machine Learning
Oct 8

RollVerify: Bridging Efficiency and Accuracy in Long-Tail Rollout Reinforcement Learning

RollVerify is a lightweight reinforcement learning framework that addresses the trade‑off between efficiency and accuracy in long‑tail rollout settings. It introduces an off‑policy shift metric (OPS) to quantify deviation in partially generated trajectories and uses sequence‑level and token‑level verification to truncate invalid suffixes before training. Experiments on mathematical reasoning tasks show that RollVerify matches on‑policy accuracy while cutting training costs, with preliminary evidence from code‑generation tasks.

By Yongqiang Yao, Jinru Tan, Kaihuan Liang, Zixin Yin, Yazhe Niu, Ruihao Gong, Dahua Lin, Ningyi Xu
arXiv Machine Learning
Oct 8

Beyond Policy Support: Interaction Constrained Offline Reinforcement Learning for Autonomous Driving

The paper introduces Interaction-Constrained Drive Policy (ICDP), an offline reinforcement learning framework for autonomous driving that explicitly controls interaction-level distribution shift. ICDP decomposes joint-support degradation into ego-support and interaction-support components, estimating the latter via contrastive density-ratio estimation without requiring joint-density modeling or simulator rollouts. Experiments on nuPlan, Interplan, and real-world truck data demonstrate that ICDP reduces selection of high-value but interaction-unsupported trajectories and improves performance in interaction-critical driving scenarios.

By Mahmoud Selim, Cristina Cipriani, Karl Henrik Johansson
arXiv Machine Learning
Oct 8

Expected Sample Complexity in Multi-Armed Bandits

The paper introduces the expected sample complexity metric for stochastic multi‑armed bandits and analyzes it within a new framework called approximately correct in expectation (ACE). It demonstrates that ACE guarantees lead to almost sure convergence to the optimal expected reward, contrasts this with high‑probability guarantees, and shows how to translate ACE bounds into explicit expected regret bounds. The authors prove that deterministic algorithms cannot achieve favorable ACE bounds, propose an explore‑then‑ε‑greedy algorithm when ε is known, analyze Thompson sampling when ε is unknown, and provide nearly matching lower bounds that establish tightness and a performance separation between the two regimes.

By Nadav Sukenik, Nadav Merlis
arXiv Machine Learning
Oct 8

Beyond Reward Suppression: Near-Optimal Offline Attacks on Warm-Start Bandits with Bounded Rewards

The paper introduces a new class of offline adversarial attacks on warm‑start bandit algorithms with bounded rewards. Unlike prior methods that suppress non‑target arms, the authors show that promoting the target arm is essential when it lies near the lower reward boundary, and they design an attack that achieves optimal sublinear cost by balancing target promotion and non‑target suppression. The attack is extended to several popular bandit algorithms and validated experimentally on real‑world and synthetic data.

By Qirun Zeng, Manhin Poon, Xiangxiang Dai, Qixin Zhang, Jinhang Zuo
arXiv Machine Learning
Oct 8

Autonomous Droplet Navigation via Model-Based Reinforcement Learning: Zero-Shot Transfer and Emergent Dynamics

The paper presents a robotic platform that enables closed‑loop autonomous navigation of liquid droplets on an open surface using model‑based reinforcement learning. A two‑axis tilting board with a silicone oil film moves the droplet while an overhead camera supplies real‑time feedback, and a policy is trained in only 50–150 physical episodes without simulation or analytical models. The system demonstrates zero‑shot transfer to unseen geometries, autonomously discovers an oscillatory depinning strategy to release stuck droplets, and completes the full training pipeline in under 90 minutes.

By Rajneesh Anand, Mayuresh V. Kothare
arXiv Machine Learning
Oct 8

Q-Learning with Scalar Adjoint Matching

The paper introduces Q‑Learning with Scalar Adjoint Matching (SQAM), a method that replaces expensive per‑step vector–Jacobian products in flow policy fine‑tuning with a closed‑form scalar adjoint that scales the value gradient by flow time. SQAM also incorporates a value penalty on policy‑generated actions, which is shown to be crucial for effective learning. Experiments demonstrate that SQAM outperforms strong baselines on the hardest OGBench domains and improves supervised fine‑tuning on a real bimanual robot with a vision‑language‑action policy.

By Yonghoon Dong, Minsung Yoon, Jaehyuk Kim, Jungwoo Park, Changyeon Kim, Jinwoo Shin
arXiv Machine Learning
Oct 8

A Good Self-Teacher Meets the Student Where They Are: Joint On-Policy Learning and Teaching

The paper introduces Joint On-Policy Learning and Teaching (JOLT), a method that trains a single policy to act both as a privileged teacher and an unprivileged student. It derives a condition ensuring the teacher’s distillation update aligns positively with the student’s reward gradient, leading to a KL‑regularized teacher objective that matches the student’s current capabilities. Experiments show JOLT improves training efficiency and performance across various tasks, with additional gains when student rewards are incorporated.

By Randy Ardywibowo, Arnav Dalal, Jiantao Jiao
arXiv Machine Learning
Oct 8

Learning Unknown Constraints without Unsafe Data via Optimality and Counterfactual Regularization

The paper introduces Counterfactual KKT (CF‑KKT), a framework that learns unknown constraints from locally optimal demonstrations without requiring known dynamics or risky exploration. CF‑KKT uses a learned differentiable dynamics model to apply KKT‑inspired optimality conditions and generates counterfactual behaviors that reveal infeasible data, enabling safer and more data‑efficient constraint recovery. Experiments on high‑dimensional robotic control tasks show that neural constraint representations learned with CF‑KKT achieve better safety and data efficiency than state‑of‑the‑art offline inverse constrained reinforcement learning baselines.

By Zhouyu Zhang, Chih-Yuan Chiu, Glen Chou
arXiv Computation and Language
Oct 8

CoTrace: Data Recipes for Training Terminal Agents with Harness-Model Co-Evolution

arXiv:2610.10426v1 Announce Type: new Abstract: Terminal-agent capability depends jointly on model weights and the runtime harness that formats prompts, binds tools, and handles error recovery. Exist...

By Jixuan Chen, Jiaxin Zhang, Qinyuan Ye, Yada Pruksachatkun, Haoxiang Zhang, Jingming Zhuo, Yifan Zhang, Yutong Dai, Juntao Tan, Xiangyu Peng, Silvio Savarese, Zeyuan Chen, Lianhui Qin, Chien-Sheng Wu
arXiv Computation and Language
Oct 8

InfiMed2: A Generalist Medical Multimodal Foundation Model from Contextual Evidence and Stability-Aware Supervision

arXiv:2609.34798v2 Announce Type: replace Abstract: Recent medical multimodal models have benefited from larger corpora, broader modality coverage, and stronger reasoning-oriented training, yet effec...

By Guanghao Zhu, Zeyu Liu, Zhitian Hou, Pengkai Wang, Zhijie Sang, Shuo Cai, Yang Yu, Yuanyi Wang, Yanggan Gu, Congkai Xie, Jianmin Wu, Hongxia Yang