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

CM-DPO: Constraint-Margin Direct Preference Optimization for LLM Planning

CM-DPO introduces a Constraint-Margin Direct Preference Optimization method that replaces the binary preference signal of traditional DPO with a continuous margin based on a deterministic symbolic verifier, scaled by violation severity. Hard and soft constraints are separated via a lexicographic objective to prevent hard constraints from being traded off against preferences. Using procedurally generated constraint profiles and minimal-edit distillation within the SynPlan-R framework, an 8B model fine‑tuned with CM‑DPO achieves high pass and solve rates on several planning benchmarks, matching multi‑agent systems with lower latency and outperforming GPT‑4o on unseen tasks.

By Rabimba Karanjai, Qun Gu, Hemanth Hegadehalli Madhavarao, Wenhuan Sun, Xiaojiao Yu, Suryabhan Singh Hada, Libin N. George, Uma Kona, Richard Williamson, Linsey Pang, Prakhar Mehrotra
arXiv Machine Learning
Oct 8

Ask the Expert: LLM-Guided Reinforcement Learning for Autonomous Cyber Defense

The paper introduces Ask the Expert, a training-time framework that leverages large language models (LLMs) to guide reinforcement learning for autonomous cyber defense. It summarizes complex cyber‑defense states, intermittently queries an LLM for host‑level defensive recommendations via a constrained action interface, and then uses those recommendations to shape rewards for PPO training. After training, the LLM is discarded, leaving a pure RL policy that improves sample efficiency and outperforms potential‑based reward shaping baselines on TTCP CAGE CC1 and CC2 scenarios.

By Fernando Martinez, Abhishek Satyam, Tao Li, Junaid Farooq, Ying Wang, Juntao Chen
arXiv Machine Learning
Oct 8

Safe on Average, Unsafe in the Tail: When Is the Episodic-Cost Tail Controllable?

The paper investigates safe reinforcement learning by focusing on the episodic-cost tail rather than just the mean cost. It introduces the use of γαρα_{0.1} (the average cost of the worst 10% of episodes) to classify policies as tail-safe. The authors evaluate standard algorithms on Safety-Gymnasium tasks, identify tail-unsafe policies, and explore constraint families to control tail violations while maintaining return.

By Samuel Tetteh, Cody Fleming
arXiv Computer Vision
Oct 8

From Digital Human Interactions to Physics-Based Humanoid Skills: Physics-Grounded Post-Training of Interaction Generators

The paper introduces DIGHT, a co‑adaptive framework that couples a Digital Human Interaction Generator with a Humanoid Tracking policy. DIGHT first runs multiple text‑conditioned interaction candidates in simulation, then builds physics‑grounded preferences from the rollouts—covering executability and interaction fidelity—and uses diffusion‑based direct preference optimization to align the generator without back‑propagating through the simulator. The aligned generator supplies reference motions for fine‑tuning the tracker, leading to more physically plausible and faithful humanoid interactions in simulation.

By Kerui Chen, Jianrong Zhang, Kai Lv, Hehe Fan
Microsoft Research
Oct 7

Agent Lightning v1.0: A 3,500-Line Lightweight Agentic RL Framework for Training Agents with Real Harnesses

Agent Lightning v1.0 is a lightweight 3,500‑line framework designed to connect existing AI agents to reinforcement learning training. It simplifies the process of improving agents by handling tools, context, and decision‑making within a single, easy‑to‑integrate system. The framework allows developers to train agents with real harnesses without the need to rebuild complex underlying structures.

By Zhiyuan He, Yuqing Yang
arXiv AI
Oct 7

Learning When to Refine: Long-Horizon Reinforcement Learning for Budgeted Neural-Operator PDE Solvers

The paper introduces a budgeted adaptive neural‑operator framework for solving time‑dependent PDEs, combining a global Fourier neural operator with a local patch‑wise residual corrector and a set‑aware selector that decides where to refine. A macro policy governs the timing and amount of refinement, and the authors propose rollout‑verified policy improvement (RV‑PI) to evaluate feasible refinement counts via actual rollouts, converting long‑horizon advantages into conservative policy targets and accepting updates only when held‑out trajectory error improves. Experiments on shallow‑water and Brusselator benchmarks show that RV‑PI outperforms immediate‑only and random macro policies, demonstrating that the value of a local correction depends on its downstream effect rather than just its immediate error reduction.

By Ange Tong