VR-Thinker: Boosting Video Reward Models through Thinking-with-Image
  Reasoning
Authors: name: Qunzhong Wang, name: Jie Liu, name: Jiajun Liang, name: Yilei Jiang, name: Yuanxing Zhang, name: Jinyuan Chen, name: Yaozhi Zheng, name: Xintao Wang, name: Pengfei Wan, name: Xiangyu Yue, name: Jiaheng Liu
Organization: NJU-LINK Lab

Recent advancements in multimodal reward models (RMs) have substantially
improved post-training for visual generative models. However, current RMs face
inherent limitations: (1) visual inputs consume large context budgets, forcing
fewer frames and causing loss of fine-grained details; and (2) all visual
information is packed into the initial prompt, exacerbating hallucination and
forgetting during chain-of-thought reasoning. To overcome these issues, we
introduce VideoReward Thinker (VR-Thinker), a thinking-with-image framework
that equips the RM with visual reasoning operations (e.g., select frame) and a
configurable visual memory window. This allows the RM to actively acquire and
update visual evidence within context limits, improving reasoning fidelity and
reliability. We activate visual reasoning via a reinforcement fine-tuning
pipeline: (i) Cold Start with curated visual chain-of-thought data to distill
basic reasoning skills and operation formatting; (ii) select samples whose
per-dimension and overall judgments are all correct, then conduct Rejection
sampling Fine-Tuning on these high-quality traces to further enhance reasoning;
and (iii) apply Group Relative Policy Optimization (GRPO) to strengthen
reasoning. Our approach delivers state-of-the-art accuracy among open-source
models on video preference benchmarks, especially for longer videos: a 7B
VR-Thinker achieves 80.5% on VideoGen Reward, 82.3% on GenAI-Bench, and 75.6%
on MJ-Bench-Video. These results validate the effectiveness and promise of
thinking-with-image multimodal reward modeling.