AREX: Towards a Recursively Self-Improving Agent for Deep Research
Authors: name: Shuqi Lu, name: Chaofan Li, name: Kun Luo, name: Zhang Zhang, name: Hui Wang, name: Hongwang Xiao, name: Zheng Liu, name: Lei Xiong, name: Jiahao Wang, name: Sen Wang, name: Xiyan Jiang, name: Wanli Li, name: Yuyang Hu, name: Hongjin Qian, name: Bingyu Yan, name: Ziyi Xia, name: Yingxia Shao, name: Kang Liu, name: Zhicheng Dou, name: Di He, name: Chaozhuo Li, name: Qiwei Ye, name: Zhongyuan Wang, name: Zheng Liu
Organization: Beijing Academy of Artificial Intelligence

Deep research requires agents to find answers that jointly satisfy multiple constraints. Discovering such answers is costly, whereas verifying a candidate can often be decomposed into tractable constraint-wise checks. This discovery--verification asymmetry suggests that a research agent should do more than simply search longer: it should recursively improve its current answer by verifying intermediate results and using the partially verified state to guide subsequent refinement. We introduce AREX, a family of Recursively Self-Improving (RSI) deep research agents. AREX alternates between an inner research loop that gathers evidence and constructs a provisional answer, and an outer self-improvement loop that audits the answer constraint-wise, identifies unresolved claims, and launches targeted follow-up research. To sustain RSI over long horizons, AREX learns an autonomous context-update tool that compresses growing interaction history into a compact improvement state preserving verified evidence and unresolved constraints, without relying on an external model. We train AREX on verified synthetic tasks and high-quality trajectories through agentic mid-training and long-horizon reinforcement learning. To mitigate sparse final rewards during long horizon learning, we emphasize key steps where decisive evidence is acquired or erroneous research directions are corrected. We instantiate a dense 4B model and a 122B-A10B Mixture-of-Experts model. Across BrowseComp, WideSearch, DeepSearchQA, Humanity's Last Exam (HLE), and other reasoning and tool-use benchmarks, AREX substantially outperforms comparable-scale baselines and remains competitive with models using substantially more activated parameters.