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Step 3.5 Flash: Open Frontier-Level Intelligence with 11B Active Parameters

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Main Authors:	Huang, Ailin, Li, Ang, Kong, Aobo, Wang, Bin, Jiao, Binxing, Dong, Bo, Wang, Bojun, Chen, Boyu, Li, Brian, Ma, Buyun, Su, Chang, Miao, Changxin, Wan, Changyi, Lou, Chao, Hu, Chen, Xu, Chen, Yu, Chenfeng, Feng, Chengting, Yao, Chengyuan, Han, Chunrui, Ma, Dan, Shi, Dapeng, Jiang, Daxin, Ma, Dehua, Sun, Deshan, Qi, Di, Liu, Enle, Zhang, Fajie, Wan, Fanqi, Huang, Guanzhe, Yan, Gulin, Cao, Guoliang, Li, Guopeng, Cheng, Han, Guo, Hangyu, Zhang, Hanshan, Nie, Hao, Jia, Haonan, Lv, Haoran, Zhou, Hebin, Lv, Hekun, Wang, Heng, Shum, Heung-Yeung, Huang, Hongbo, Peng, Hongbo, Zhou, Hongyu, Wang, Hongyuan, Chen, Houyong, Zhu, Huangxi, Wu, Huimin, Guo, Huiyong, Wang, Jia, Zhou, Jian, Sun, Jianjian, Wu, Jiaoren, Zhang, Jiaran, Lv, Jiashu, Liu, Jiashuo, Fu, Jiayi, Liu, Jiayu, Cheng, Jie, Luo, Jie, Yang, Jie, Zhou, Jie, Hou, Jieyi, Bai, Jing, Hu, Jingcheng, Xie, Jingjing, Wu, Jingwei, Zhang, Jingyang, Zhou, Jishi, Liu, Junfeng, Lin, Junzhe, Lo, Ka Man, Liang, Kai, Liu, Kaibo, Tan, Kaijun, Yan, Kaiwen, Li, Kaixiang, An, Kang, Lin, Kangheng, Yang, Lei, Lv, Liang, Zhao, Liang, Chen, Liangyu, Shi, Lieyu, Tan, Liguo, Lin, Lin, Chen, Lina, Ma, Luck, Ren, Mengqiang, Li, Michael, Li, Ming, Li, Mingliang, Zhang, Mingming, Chen, Mingrui, Huang, Mitt, Wang, Na, Liu, Peng, Han, Qi, Zhao, Qian, He, Qinglin, Du, Qinxin, Wu, Qiuping, Sun, Quan, Yang, Rongqiu, Miao, Ruihang, Han, Ruixin, Wan, Ruosi, Guo, Ruyan, Wang, Shan, Pang, Shaoliang, Yang, Shaowen, Fan, Shengjie, Shang, Shijie, Yang, Shiliang, Li, Shiwei, Tian, Shuangshuang, Liu, Siqi, Wu, Siye, Chen, Siyu, Yuan, Song, Cao, Tiancheng, Yue, Tianchi, Cheng, Tianhao, Li, Tianning, Luo, Tingdan, You, Wang, Ji, Wei, Yuan, Wei, Zhang, Wei, Wu, Weibo, Xie, Weihao, Sun, Wen, Deng, Wenjin, Zheng, Wenzhen, Xie, Wuxun, Wang, Xiangfeng, Kong, Xiangwen, Liu, Xiangyu, Zhang, Xiangyu, Yang, Xiaobo, Liu, Xiaojia, Yuan, Xiaolan, Jiao, Xiaoran, Ren, Xiaoxiao, Zhang, Xiaoyun, Li, Xin, Liu, Xin, Wu, Xin, Chen, Xing, Yang, Xingping, Wang, Xinran, Zhao, Xu, He, Xuan, Feng, Xuanti, Cai, Xuedan, Zhou, Xuqiang, Yu, Yanbo, Li, Yang, Xu, Yang, Lai, Yanlin, Xu, Yanming, Wang, Yaoyu, Shen, Yeqing, Zhu, Yibo, Lv, Yichen, Cao, Yicheng, Gong, Yifeng, Yang, Yijing, Yang, Yikun, Zhao, Yin, Zhao, Yingxiu, Zhang, Yinmin, Zhang, Yitong, Zhang, Yixuan, Chen, Yiyang, Zhao, Yongchi, Long, Yongshen, Wang, Yongyao, Guan, Yousong, Zhou, Yu, Peng, Yuang, Ding, Yuanhao, Fan, Yuantao, Lu, Yuanwei, Yang, Yuanzhen, Luo, Yuchu, Zhao, Yudi, Peng, Yue, Lin, Yueqiang, Lu, Yufan, Zhao, Yuling, Ju, Yunzhou, Zhang, Yurong, Li, Yusheng, Yang, Yuxiang, Chen, Yuyang, Cai, Yuzhu, Weng, Zejia, Hong, Zetao, Li, Zexi, Xie, Zhe, Ge, Zheng, Gong, Zheng, Zeng, Zheng, Lu, Zhenyi, Huang, Zhewei, Chang, Zhichao, Huang, Zhiguo, Hu, Zhiheng, Yang, Zidong, Wang, Zili, Ren, Ziqi, Zhang, Zixin, Wang, Zixuan
Format:	Preprint
Published:	2026
Subjects:	Computation and Language Artificial Intelligence
Online Access:	Acceder al recurso
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_version_	1866911462348292096
author	Huang, Ailin Li, Ang Kong, Aobo Wang, Bin Jiao, Binxing Dong, Bo Wang, Bojun Chen, Boyu Li, Brian Ma, Buyun Su, Chang Miao, Changxin Wan, Changyi Lou, Chao Hu, Chen Xu, Chen Yu, Chenfeng Feng, Chengting Yao, Chengyuan Han, Chunrui Ma, Dan Shi, Dapeng Jiang, Daxin Ma, Dehua Sun, Deshan Qi, Di Liu, Enle Zhang, Fajie Wan, Fanqi Huang, Guanzhe Yan, Gulin Cao, Guoliang Li, Guopeng Cheng, Han Guo, Hangyu Zhang, Hanshan Nie, Hao Jia, Haonan Lv, Haoran Zhou, Hebin Lv, Hekun Wang, Heng Shum, Heung-Yeung Huang, Hongbo Peng, Hongbo Zhou, Hongyu Wang, Hongyuan Chen, Houyong Zhu, Huangxi Wu, Huimin Guo, Huiyong Wang, Jia Zhou, Jian Sun, Jianjian Wu, Jiaoren Zhang, Jiaran Lv, Jiashu Liu, Jiashuo Fu, Jiayi Liu, Jiayu Cheng, Jie Luo, Jie Yang, Jie Zhou, Jie Hou, Jieyi Bai, Jing Hu, Jingcheng Xie, Jingjing Wu, Jingwei Zhang, Jingyang Zhou, Jishi Liu, Junfeng Lin, Junzhe Lo, Ka Man Liang, Kai Liu, Kaibo Tan, Kaijun Yan, Kaiwen Li, Kaixiang An, Kang Lin, Kangheng Yang, Lei Lv, Liang Zhao, Liang Chen, Liangyu Shi, Lieyu Tan, Liguo Lin, Lin Chen, Lina Ma, Luck Ren, Mengqiang Li, Michael Li, Ming Li, Mingliang Zhang, Mingming Chen, Mingrui Huang, Mitt Wang, Na Liu, Peng Han, Qi Zhao, Qian He, Qinglin Du, Qinxin Wu, Qiuping Sun, Quan Yang, Rongqiu Miao, Ruihang Han, Ruixin Wan, Ruosi Guo, Ruyan Wang, Shan Pang, Shaoliang Yang, Shaowen Fan, Shengjie Shang, Shijie Yang, Shiliang Li, Shiwei Tian, Shuangshuang Liu, Siqi Wu, Siye Chen, Siyu Yuan, Song Cao, Tiancheng Yue, Tianchi Cheng, Tianhao Li, Tianning Luo, Tingdan You, Wang Ji, Wei Yuan, Wei Zhang, Wei Wu, Weibo Xie, Weihao Sun, Wen Deng, Wenjin Zheng, Wenzhen Xie, Wuxun Wang, Xiangfeng Kong, Xiangwen Liu, Xiangyu Zhang, Xiangyu Yang, Xiaobo Liu, Xiaojia Yuan, Xiaolan Jiao, Xiaoran Ren, Xiaoxiao Zhang, Xiaoyun Li, Xin Liu, Xin Wu, Xin Chen, Xing Yang, Xingping Wang, Xinran Zhao, Xu He, Xuan Feng, Xuanti Cai, Xuedan Zhou, Xuqiang Yu, Yanbo Li, Yang Xu, Yang Lai, Yanlin Xu, Yanming Wang, Yaoyu Shen, Yeqing Zhu, Yibo Lv, Yichen Cao, Yicheng Gong, Yifeng Yang, Yijing Yang, Yikun Zhao, Yin Zhao, Yingxiu Zhang, Yinmin Zhang, Yitong Zhang, Yixuan Chen, Yiyang Zhao, Yongchi Long, Yongshen Wang, Yongyao Guan, Yousong Zhou, Yu Peng, Yuang Ding, Yuanhao Fan, Yuantao Lu, Yuanwei Yang, Yuanzhen Luo, Yuchu Zhao, Yudi Peng, Yue Lin, Yueqiang Lu, Yufan Zhao, Yuling Ju, Yunzhou Zhang, Yurong Li, Yusheng Yang, Yuxiang Chen, Yuyang Cai, Yuzhu Weng, Zejia Hong, Zetao Li, Zexi Xie, Zhe Ge, Zheng Gong, Zheng Zeng, Zheng Lu, Zhenyi Huang, Zhewei Chang, Zhichao Huang, Zhiguo Hu, Zhiheng Yang, Zidong Wang, Zili Ren, Ziqi Zhang, Zixin Wang, Zixuan
author_facet	Huang, Ailin Li, Ang Kong, Aobo Wang, Bin Jiao, Binxing Dong, Bo Wang, Bojun Chen, Boyu Li, Brian Ma, Buyun Su, Chang Miao, Changxin Wan, Changyi Lou, Chao Hu, Chen Xu, Chen Yu, Chenfeng Feng, Chengting Yao, Chengyuan Han, Chunrui Ma, Dan Shi, Dapeng Jiang, Daxin Ma, Dehua Sun, Deshan Qi, Di Liu, Enle Zhang, Fajie Wan, Fanqi Huang, Guanzhe Yan, Gulin Cao, Guoliang Li, Guopeng Cheng, Han Guo, Hangyu Zhang, Hanshan Nie, Hao Jia, Haonan Lv, Haoran Zhou, Hebin Lv, Hekun Wang, Heng Shum, Heung-Yeung Huang, Hongbo Peng, Hongbo Zhou, Hongyu Wang, Hongyuan Chen, Houyong Zhu, Huangxi Wu, Huimin Guo, Huiyong Wang, Jia Zhou, Jian Sun, Jianjian Wu, Jiaoren Zhang, Jiaran Lv, Jiashu Liu, Jiashuo Fu, Jiayi Liu, Jiayu Cheng, Jie Luo, Jie Yang, Jie Zhou, Jie Hou, Jieyi Bai, Jing Hu, Jingcheng Xie, Jingjing Wu, Jingwei Zhang, Jingyang Zhou, Jishi Liu, Junfeng Lin, Junzhe Lo, Ka Man Liang, Kai Liu, Kaibo Tan, Kaijun Yan, Kaiwen Li, Kaixiang An, Kang Lin, Kangheng Yang, Lei Lv, Liang Zhao, Liang Chen, Liangyu Shi, Lieyu Tan, Liguo Lin, Lin Chen, Lina Ma, Luck Ren, Mengqiang Li, Michael Li, Ming Li, Mingliang Zhang, Mingming Chen, Mingrui Huang, Mitt Wang, Na Liu, Peng Han, Qi Zhao, Qian He, Qinglin Du, Qinxin Wu, Qiuping Sun, Quan Yang, Rongqiu Miao, Ruihang Han, Ruixin Wan, Ruosi Guo, Ruyan Wang, Shan Pang, Shaoliang Yang, Shaowen Fan, Shengjie Shang, Shijie Yang, Shiliang Li, Shiwei Tian, Shuangshuang Liu, Siqi Wu, Siye Chen, Siyu Yuan, Song Cao, Tiancheng Yue, Tianchi Cheng, Tianhao Li, Tianning Luo, Tingdan You, Wang Ji, Wei Yuan, Wei Zhang, Wei Wu, Weibo Xie, Weihao Sun, Wen Deng, Wenjin Zheng, Wenzhen Xie, Wuxun Wang, Xiangfeng Kong, Xiangwen Liu, Xiangyu Zhang, Xiangyu Yang, Xiaobo Liu, Xiaojia Yuan, Xiaolan Jiao, Xiaoran Ren, Xiaoxiao Zhang, Xiaoyun Li, Xin Liu, Xin Wu, Xin Chen, Xing Yang, Xingping Wang, Xinran Zhao, Xu He, Xuan Feng, Xuanti Cai, Xuedan Zhou, Xuqiang Yu, Yanbo Li, Yang Xu, Yang Lai, Yanlin Xu, Yanming Wang, Yaoyu Shen, Yeqing Zhu, Yibo Lv, Yichen Cao, Yicheng Gong, Yifeng Yang, Yijing Yang, Yikun Zhao, Yin Zhao, Yingxiu Zhang, Yinmin Zhang, Yitong Zhang, Yixuan Chen, Yiyang Zhao, Yongchi Long, Yongshen Wang, Yongyao Guan, Yousong Zhou, Yu Peng, Yuang Ding, Yuanhao Fan, Yuantao Lu, Yuanwei Yang, Yuanzhen Luo, Yuchu Zhao, Yudi Peng, Yue Lin, Yueqiang Lu, Yufan Zhao, Yuling Ju, Yunzhou Zhang, Yurong Li, Yusheng Yang, Yuxiang Chen, Yuyang Cai, Yuzhu Weng, Zejia Hong, Zetao Li, Zexi Xie, Zhe Ge, Zheng Gong, Zheng Zeng, Zheng Lu, Zhenyi Huang, Zhewei Chang, Zhichao Huang, Zhiguo Hu, Zhiheng Yang, Zidong Wang, Zili Ren, Ziqi Zhang, Zixin Wang, Zixuan
contents	We introduce Step 3.5 Flash, a sparse Mixture-of-Experts (MoE) model that bridges frontier-level agentic intelligence and computational efficiency. We focus on what matters most when building agents: sharp reasoning and fast, reliable execution. Step 3.5 Flash pairs a 196B-parameter foundation with 11B active parameters for efficient inference. It is optimized with interleaved 3:1 sliding-window/full attention and Multi-Token Prediction (MTP-3) to reduce the latency and cost of multi-round agentic interactions. To reach frontier-level intelligence, we design a scalable reinforcement learning framework that combines verifiable signals with preference feedback, while remaining stable under large-scale off-policy training, enabling consistent self-improvement across mathematics, code, and tool use. Step 3.5 Flash demonstrates strong performance across agent, coding, and math tasks, achieving 85.4% on IMO-AnswerBench, 86.4% on LiveCodeBench-v6 (2024.08-2025.05), 88.2% on tau2-Bench, 69.0% on BrowseComp (with context management), and 51.0% on Terminal-Bench 2.0, comparable to frontier models such as GPT-5.2 xHigh and Gemini 3.0 Pro. By redefining the efficiency frontier, Step 3.5 Flash provides a high-density foundation for deploying sophisticated agents in real-world industrial environments.
format	Preprint
id	arxiv_https___arxiv_org_abs_2602_10604
institution	arXiv
publishDate	2026
record_format	arxiv
spellingShingle	Step 3.5 Flash: Open Frontier-Level Intelligence with 11B Active Parameters Huang, Ailin Li, Ang Kong, Aobo Wang, Bin Jiao, Binxing Dong, Bo Wang, Bojun Chen, Boyu Li, Brian Ma, Buyun Su, Chang Miao, Changxin Wan, Changyi Lou, Chao Hu, Chen Xu, Chen Yu, Chenfeng Feng, Chengting Yao, Chengyuan Han, Chunrui Ma, Dan Shi, Dapeng Jiang, Daxin Ma, Dehua Sun, Deshan Qi, Di Liu, Enle Zhang, Fajie Wan, Fanqi Huang, Guanzhe Yan, Gulin Cao, Guoliang Li, Guopeng Cheng, Han Guo, Hangyu Zhang, Hanshan Nie, Hao Jia, Haonan Lv, Haoran Zhou, Hebin Lv, Hekun Wang, Heng Shum, Heung-Yeung Huang, Hongbo Peng, Hongbo Zhou, Hongyu Wang, Hongyuan Chen, Houyong Zhu, Huangxi Wu, Huimin Guo, Huiyong Wang, Jia Zhou, Jian Sun, Jianjian Wu, Jiaoren Zhang, Jiaran Lv, Jiashu Liu, Jiashuo Fu, Jiayi Liu, Jiayu Cheng, Jie Luo, Jie Yang, Jie Zhou, Jie Hou, Jieyi Bai, Jing Hu, Jingcheng Xie, Jingjing Wu, Jingwei Zhang, Jingyang Zhou, Jishi Liu, Junfeng Lin, Junzhe Lo, Ka Man Liang, Kai Liu, Kaibo Tan, Kaijun Yan, Kaiwen Li, Kaixiang An, Kang Lin, Kangheng Yang, Lei Lv, Liang Zhao, Liang Chen, Liangyu Shi, Lieyu Tan, Liguo Lin, Lin Chen, Lina Ma, Luck Ren, Mengqiang Li, Michael Li, Ming Li, Mingliang Zhang, Mingming Chen, Mingrui Huang, Mitt Wang, Na Liu, Peng Han, Qi Zhao, Qian He, Qinglin Du, Qinxin Wu, Qiuping Sun, Quan Yang, Rongqiu Miao, Ruihang Han, Ruixin Wan, Ruosi Guo, Ruyan Wang, Shan Pang, Shaoliang Yang, Shaowen Fan, Shengjie Shang, Shijie Yang, Shiliang Li, Shiwei Tian, Shuangshuang Liu, Siqi Wu, Siye Chen, Siyu Yuan, Song Cao, Tiancheng Yue, Tianchi Cheng, Tianhao Li, Tianning Luo, Tingdan You, Wang Ji, Wei Yuan, Wei Zhang, Wei Wu, Weibo Xie, Weihao Sun, Wen Deng, Wenjin Zheng, Wenzhen Xie, Wuxun Wang, Xiangfeng Kong, Xiangwen Liu, Xiangyu Zhang, Xiangyu Yang, Xiaobo Liu, Xiaojia Yuan, Xiaolan Jiao, Xiaoran Ren, Xiaoxiao Zhang, Xiaoyun Li, Xin Liu, Xin Wu, Xin Chen, Xing Yang, Xingping Wang, Xinran Zhao, Xu He, Xuan Feng, Xuanti Cai, Xuedan Zhou, Xuqiang Yu, Yanbo Li, Yang Xu, Yang Lai, Yanlin Xu, Yanming Wang, Yaoyu Shen, Yeqing Zhu, Yibo Lv, Yichen Cao, Yicheng Gong, Yifeng Yang, Yijing Yang, Yikun Zhao, Yin Zhao, Yingxiu Zhang, Yinmin Zhang, Yitong Zhang, Yixuan Chen, Yiyang Zhao, Yongchi Long, Yongshen Wang, Yongyao Guan, Yousong Zhou, Yu Peng, Yuang Ding, Yuanhao Fan, Yuantao Lu, Yuanwei Yang, Yuanzhen Luo, Yuchu Zhao, Yudi Peng, Yue Lin, Yueqiang Lu, Yufan Zhao, Yuling Ju, Yunzhou Zhang, Yurong Li, Yusheng Yang, Yuxiang Chen, Yuyang Cai, Yuzhu Weng, Zejia Hong, Zetao Li, Zexi Xie, Zhe Ge, Zheng Gong, Zheng Zeng, Zheng Lu, Zhenyi Huang, Zhewei Chang, Zhichao Huang, Zhiguo Hu, Zhiheng Yang, Zidong Wang, Zili Ren, Ziqi Zhang, Zixin Wang, Zixuan Computation and Language Artificial Intelligence We introduce Step 3.5 Flash, a sparse Mixture-of-Experts (MoE) model that bridges frontier-level agentic intelligence and computational efficiency. We focus on what matters most when building agents: sharp reasoning and fast, reliable execution. Step 3.5 Flash pairs a 196B-parameter foundation with 11B active parameters for efficient inference. It is optimized with interleaved 3:1 sliding-window/full attention and Multi-Token Prediction (MTP-3) to reduce the latency and cost of multi-round agentic interactions. To reach frontier-level intelligence, we design a scalable reinforcement learning framework that combines verifiable signals with preference feedback, while remaining stable under large-scale off-policy training, enabling consistent self-improvement across mathematics, code, and tool use. Step 3.5 Flash demonstrates strong performance across agent, coding, and math tasks, achieving 85.4% on IMO-AnswerBench, 86.4% on LiveCodeBench-v6 (2024.08-2025.05), 88.2% on tau2-Bench, 69.0% on BrowseComp (with context management), and 51.0% on Terminal-Bench 2.0, comparable to frontier models such as GPT-5.2 xHigh and Gemini 3.0 Pro. By redefining the efficiency frontier, Step 3.5 Flash provides a high-density foundation for deploying sophisticated agents in real-world industrial environments.
title	Step 3.5 Flash: Open Frontier-Level Intelligence with 11B Active Parameters
topic	Computation and Language Artificial Intelligence
url	https://arxiv.org/abs/2602.10604