Reinforcement learning

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

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arXiv AI
Sep 10

Flow3D-OPD: Multi-Teacher On-Policy Distillation for 3D Geometry Generation with Flow-Matching Diffusion Transformer

arXiv:2609.07137v1 Announce Type: cross Abstract: Recent image-to-3D generation models built on flow-matching diffusion Transformers (DiT) can produce high-fidelity meshes, yet their post-training st...

By Zhiwei Ning, Zhen Zhou, Puhua Jiang, Xintong Han, Gengming Zhang, Jie Yang, Zhonglong Zheng, Yuanjie Zheng, Wei Liu, Chunchao Guo
arXiv Machine Learning
Sep 10

CoRL: Co-Evolutionary Reinforcement Learning for Adaptive Indirect Prompt-Injection Attacks and Defenses

The paper introduces CoRL, a co-evolutionary reinforcement learning framework designed to defend against adaptive indirect prompt-injection attacks on tool-augmented language agents. CoRL operates in three stages—attacker fine‑tuning, bilateral Co‑PPO training, and defender fine‑tuning—using verifier‑grounded repairs to adapt to changing attack strategies. Experiments on 1,514 executions show that CoRL reduces attack success rates to 0% while improving task utility, demonstrating its effectiveness against adaptive adversaries.

By Boyang Zhang, Qingxin Xiao, Lingwei Dang, Qingyao Wu
arXiv AI
Sep 10

Steering Geometry: Validating Human Value Geometry in LLM Steering Space

arXiv:2609.06289v1 Announce Type: cross Abstract: As large language models (LLMs) are increasingly deployed in alignment-sensitive contexts, activation steering has emerged as a lightweight, inferenc...

By Mohammad Mahdi Abootorabi, Armin Saghafian, Ali Bazshoushtari, Hamid Rezaei, EunJeong Hwang, Vered Shwartz, Parvin Mousavi, Purang Abolmaesumi
arXiv AI
Sep 10

Environments as Scaffold: Enriching Feedback to Bootstrap Self-Evolving Agents in Long-Horizon Tasks

The paper introduces Feedback‑Enriched Environments (FEEs) as a new approach to training large language models as autonomous agents for long‑horizon tasks. By shifting from action guidance to observation enrichment during later stages of exploration, FEEs improve performance across SciWorld and BFCL benchmarks with various Qwen3 model scales and RL algorithms. The study shows that FEEs stabilize training, promote proactive exploration, embed environmental guidance into policy weights, and highlight intra‑group feedback consistency as key for stable optimization.

By Hongbang Yuan, Zhuoran Jin, Yixin Cao
arXiv AI
Sep 10

HyCO: A Hybrid Neural Solver for Combinatorial Optimization

HyCO is a hybrid neural solver that combines a sequential reinforcement learning (RL) solver with a global diffusion model (DM) to tackle combinatorial optimization problems. The RL component builds an initial solution prefix, after which HyCO switches to a conditional DM to finish the remaining decisions. The authors provide a theoretical framework showing that this hybrid approach yields lower expected regret than either method alone, identify an optimal trigger step for the switch, and implement a lightweight adaptive trigger based on policy entropy and RL‑DM disagreement, achieving consistent performance gains across benchmarks.

By Yuheng Li, Di Yang, Haipeng Chen, Yanhai Xiong
arXiv AI
Sep 10

You Can't Prefer Emotions You Don't Sample: Intensity Undershoot in DPO-Tuned LLMs

The study shows that instruction‑tuned language models, when asked to generate responses with varying emotional intensity, consistently undershoot the requested affect. By conditioning a model on continuous Valence‑Arousal targets and measuring output with a frozen regressor, the authors find that the gain for valence is only 0.26 and for arousal 0.13 on Llama‑3.1‑8B, far below the ideal value of 1. They trace this undershoot to the preference‑learning pipeline: training data such as EmoBank are neutral‑heavy and the candidate pool rarely contains extreme affect, so Direct Preference Optimization lacks examples to learn from. Expanding the target space uniformly and sampling a hotter, larger candidate pool raises valence gain to 0.40 and improves extrapolation with minimal in‑distribution cost, a result that also holds for Qwen3‑8B. Arousal remains more variable because the base model rarely generates highly aroused candidates.

By Hyunwoo Kim, Usama Khalid
arXiv AI
Sep 10

Tracking the Moving Frontier: Long-Short Term Advantage Estimator

The paper introduces Long-Short Term Advantage Estimator (LSTAE), a single‑stream reinforcement learning algorithm that replaces repeated within‑iteration trajectory sampling with historical experience for advantage estimation. LSTAE tracks each task anchor with a drift‑aware long‑term baseline and a short‑term state‑experience buffer, converting accumulated experience into multi‑granular credit signals while requiring only one rollout per anchor. Experiments on agentic and mathematical reasoning benchmarks show that LSTAE matches or surpasses strong group‑based baselines while significantly reducing rollout cost.

By Xinhao Yao, Lu Yu, Changhao Wang, Fengwei Teng, Yuyao Zhang, Qing Cui, Jun Zhou, Yong Liu
arXiv AI
Sep 10

Damage-Aware Bandit Pruning for Vision and Language Transformers

The paper introduces a structured post‑training pruning method for vision and language transformers called Damage‑Aware Bandit Pruning. It treats the selection of functional units (attention heads and MLP channel groups) as a multi‑armed bandit problem, using paired damage (masked loss minus base loss) as a reward to guide either UCB or Thompson Sampling policies. Experiments on a range of models (GPT‑2, OPT, Pythia, Qwen2.5, SmolLM2, ViT‑B/16, DeiT‑Tiny, Swin‑Tiny) show that the bandit approaches generally reduce degradation compared to budgeted‑greedy baselines, with statistically significant improvements in most comparisons.

By Salem Ameen, Sunil Vadera