Authors

Zhen Zhang

Publications 2

Preprint Open access

CriticHack: Evaluating Visual Rewards Under Robot Policy Optimization

Jiaxuan Luo, Xingguo Xu, Shanshan Wang et al. · 2026

Learned visual reward models are increasingly used to optimize robot policies, yet a reward model can score an execution that acts on the wrong object as highly as one that completes the task. We show that optimizing such a reward can amplify these wrong-object failures while reward and task success both rise, so the s …

Preprint Open access

Dependency-Aware Trajectory Refinement for Efficient Multi-Turn Agent Fine-Tuning

Zhuo Chen, Zhen Zhang, Xinyu Wang et al. · 2026

Multi-turn agent trajectories often contain redundant rounds (failed tool calls, parallel sub-queries, verification-only steps) that inflate both training and inference cost. We propose viewing each trajectory as a \emph{round-level dependency DAG} that exposes which rounds are globally load-bearing for the final answe …

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