LongCat-Flash-Thinking-2601 Technical Report
Abstract
We introduce LongCat-Flash-Thinking-2601, a 560-billion-parameter open-source Mixture-of-Experts (MoE) reasoning model with superior agentic reasoning capability. LongCat-Flash-Thinking-2601 achieves state-of-the-art performance among open-source models on a wide range of agentic benchmarks, including agentic search, agentic tool use, and tool-integrated reasoning. Beyond benchmark performance, the model demonstrates strong generalization to complex tool interactions and robust behavior under noisy real-world environments. Its advanced capability stems from a unified training framework that combines domain-parallel expert training with subsequent fusion, together with an end-to-end co-design of data construction, environments, algorithms, and infrastructure spanning from pre-training to post-training. In particular, the model's strong generalization capability in complex tool-use are driven by our in-depth exploration of environment scaling and principled task construction. To optimize long-tailed, skewed generation and multi-turn agentic interactions, and to enable stable training across over 10,000 environments spanning more than 20 domains, we systematically extend our asynchronous reinforcement learning framework, DORA, for stable and efficient large-scale multi-environment training. Furthermore, recognizing that real-world tasks are inherently noisy, we conduct a systematic analysis and decomposition of real-world noise patterns, and design targeted training procedures to explicitly incorporate such imperfections into the training process, resulting in improved robustness for real-world applications. To further enhance performance on complex reasoning tasks, we introduce a Heavy Thinking mode that enables effective test-time scaling by jointly expanding reasoning depth and width through intensive parallel thinking.
Cite
@article{arxiv.2601.16725,
title = {LongCat-Flash-Thinking-2601 Technical Report},
author = {Meituan LongCat Team and Anchun Gui and Bei Li and Bingyang Tao and Bole Zhou and Borun Chen and Chao Zhang and Chao Zhang and Chen Gao and Chen Zhang and Chengcheng Han and Chenhui Yang and Chuyu Zhang and Cong Chen and Cunguang Wang and Daoru Pan and Defei Bu and Dengchang Zhao and Di Xiu and Dishan Liu and Dongyu Ru and Dunwei Tu and Fan Wu and Fengcheng Yuan and Fengcun Li and Gang Xu and Guanyu Wu and Guoyuan Lin and Haibin Wang and Hansi Yang and Hao Yang and Haonan Yan and Haoxiang Ma and Haoxing Wen and Hongyan Hao and Hongyin Tang and Hongyu Zang and Hongzhi Ni and Hui Su and Jiacheng Zhang and Jiahong Zhou and Jiahuan Li and Jiaming Wang and Jian Yang and Jianfei Zhang and Jianhao Xu and Jianing Wang and Jiapeng Zhu and Jiaqi Sun and Jiarong Shi and Jiarui Zhao and Jingang Wang and Jinluan Yang and Jinrui Ding and Jinwei Xiao and Jiyuan He and Juncan Xu and Kefeng Zhang and Keheng Wang and Li Wei and Lianhui Ma and Lin Qiu and Lingbing Kong and Lingchuan Liu and Linsen Guo and Mengshen Zhu and Mengxia Shen and Mingyang Zhu and Peiguang Li and Peng Pei and Peng Zhao and Pengcheng Jia and Pengtao Zhang and Ping Liu and Qi Gu and Qiong Huang and Qiyuan Duan and Quanchi Weng and Rongxiang Weng and Rongzhi Zhang and Rumei Li and Shanglin Lei and Shengnan An and Shijun Dai and Shizhe Wu and Shuaikang Liu and Shuang Zhou and Shuo Wang and Songyuan Zhao and Tao Liang and Tianhao Hu and Tianze Chen and Wei Liu and Wei Shi and Wei Wang and Weifeng Tang and Wenjie Shi and Wenlong Zhu and Wentao Chen and Wentao Shi and Xi Su and Xiandi Ma and Xiangcheng Liu and Xiangyu Xi and Xiangyuan Liu and Xiangzhou Huang and Xiao Liu and Xiaodong Cai and Xiaolong Chen and Xiaowei Shi and Xiaoyu Li and Xin Chen and Xingchen Liu and Xuan Huang and Xuezhi Cao and Xunliang Cai and Yan Chen and Yang Bai and Yang Liu and Yang Yang and Yang Zheng and Yanyu Chen and Yaoming Wang and Yaoming Zhu and Yaorui Shi and Yaqi Huo and Yerui Sun and Yi Zhang and Yi-Kai Zhang and Yifan Lu and Yifan Zhao and Yihao Chen and Yitao Zhai and Yongjing Yin and Yongwei Zhou and Youshao Xiao and Yu Wang and Yu Yang and Yuchen Xie and Yuchen Yu and Yuchuan Dai and Yue Xu and Yueqing Sun and Yufei Zhang and Yuhuai Wei and Yulei Qian and Yunfan Liang and Yunke Zhao and Yuwei Jiang and Yuxin Bian and Yuxin Chen and Yuxin Liu and Zeyang Yu and Zhao Yang and Zhengsheng Huang and Zhengyu Chen and Zhijian Liu and Zhikang Xia and Zhimin Lin and Zhiyuan Yao and Zhuofan Chen and Zhuowen Han and Zijian Zhang and Ziran Li and Ziwen Wang and Ziyuan Zhuang},
journal= {arXiv preprint arXiv:2601.16725},
year = {2026}
}