这篇论文用奖励方差自动发现困难样本并生成新数据，训练效率比静态数据高20倍，特别适合多轮工具智能体场景。
多轮工具使用强化学习受限于静态数据集中信息样本快速耗尽的问题。研究观察到GRPO中梯度集中在高奖励方差任务上，基于Popoviciu上界。提出RODS方法，利用进度奖励方差作为零成本边界检测器，无需额外推理。通过技能对齐重采样管道合成新多轮变体，维护动态缓冲池。从400个人工种子开始，保持约800样本活跃池，达到与17K样本离线管道相当性能，轨迹数减少约20倍。
RODS: Reward-Driven Online Data Synthesis for Multi-Turn Tool-Use Agents
Multi-turn tool-use RL is bottlenecked by the rapid depletion of informative samples in static datasets. We observe that the gradient signal in GRPO concentrates on tasks with the highest rollout reward variance, a consequence of the Popoviciu upper bound. Consequently, samples near the agent's capability boundary -- where successes and failures are roughly balanced -- contribute disproportionately large policy gradients. As training progresses, this boundary continuously shifts, which gradually depletes the pool of informative samples in a static dataset. We propose RODS (Reward-driven Online Data Synthesis) to resolve this depletion. RODS closes the loop between RL training and data generation by repurposing the progress reward variance as a practical, zero-cost boundary detector that requires no extra inference beyond the rollouts already computed for training. It continuously identifies such boundary samples, synthesizes new multi-turn variants matching their structural complexity (e.g., API topology and dependency depth) via a skill-aligned resampling pipeline, and manages a dynamic replay buffer that co-evolves with the policy. Starting from 400 human seeds and maintaining an active training pool of ~800 samples, RODS achieves comparable performance to a 17K-sample offline pipeline while requiring roughly 20x fewer trajectories, and improves over fixed-data RL and environment augmentation in our controlled setting.