WebSailor-V2: Bridging the Chasm to Proprietary Agents via Synthetic Data and Scalable Reinforcement Learning

Kuan Li; Zhongwang Zhang; Huifeng Yin; Rui Ye; Yida Zhao; Liwen Zhang; Litu Ou; Dingchu Zhang; Xixi Wu; Jialong Wu; Xinyu Wang; Zile Qiao; Zhen Zhang; Yong Jiang; Pengjun Xie; Fei Huang; Jingren Zhou

arXiv · 2509.13305

WebSailor-V2: Bridging the Chasm to Proprietary Agents via Synthetic Data and Scalable Reinforcement Learning

Kuan Li·Zhongwang Zhang·Huifeng Yin·Rui Ye·Yida Zhao·Liwen Zhang·Litu Ou·Dingchu Zhang·Xixi Wu·Jialong Wu·Xinyu Wang·Zile Qiao·Zhen Zhang·Yong Jiang·Pengjun Xie·Fei Huang·Jingren Zhou

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Abstract

Transcending human cognitive limitations represents a critical frontier in LLM training. Proprietary agentic systems like DeepResearch have demonstrated superhuman capabilities on extremely complex information-seeking benchmarks such as BrowseComp, a feat previously unattainable. We posit that their success hinges on a sophisticated reasoning pattern absent in open-source models: the ability to systematically reduce extreme uncertainty when navigating vast information landscapes. Based on this insight, we introduce WebSailor, a complete post-training methodology designed to instill this crucial capability. Our approach involves generating novel, high-uncertainty tasks through structured sampling and information obfuscation, RFT cold start, and an efficient agentic RL training algorithm, Duplicating Sampling Policy Optimization (DUPO). With this integrated pipeline, WebSailor significantly outperforms all open-source agents in complex information-seeking tasks, matching proprietary agents' performance and closing the capability gap.

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Kuan Li, Zhongwang Zhang, Huifeng Yin, Rui Ye, Yida Zhao, Liwen Zhang, Litu Ou, Dingchu Zhang, Xixi Wu, Jialong Wu, Xinyu Wang, Zile Qiao, Zhen Zhang, Yong Jiang, Pengjun Xie, Fei Huang, Jingren Zhou. 2025-09-16. WebSailor-V2: Bridging the Chasm to Proprietary Agents via Synthetic Data and Scalable Reinforcement Learning. https://arxiv.org/abs/2509.13305

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