StepFun has launched Step 5 Preview, a new flagship model for agentic work with 600B total parameters. The company announced the model in a post on X and says it plans to release open weights on October 15, 2026; API access started September 20, 2026.
StepFun says the model is built for software engineering and professional knowledge work, with particular strength in finance. Its documentation lists a 1 million-token context window, output of up to 64,000 tokens, and support for text, image and video inputs. The company also lists long-context understanding, software engineering, multimodal analysis and multi-step tasks that use tools for research, document processing and analytical work.
Secondary reporting describes the model as a 600B-total, 27B-active sparse Mixture-of-Experts model with a 92-layer Transformer design. In company-reported high-effort results, Step 5 Preview scored 66.4 on FrontierFinance and 67.7% on DeepSWE v1.1. Artificial Analysis scored the model 44 on its Intelligence Index.
Reported API pricing is $1.00 per million input tokens on cache misses, $0.05 per million input tokens on cache hits and $2.70 per million output tokens.
StepFun was founded in Shanghai on April 6, 2023 by Jiang Daxin, Zhu Yibo and Jiao Binxing. StepFun is one of China's so-called “Six AI Tigers,” a group of independent large-model startups alongside Z.ai, Moonshot AI, MiniMax, Baichuan and 01.AI.
Its earlier open-weight releases include Step 3.5 Flash, a 196B-total, 11B-active MoE model released in February 2026, and Step 3.7 Flash, released in May 2026. Both were released under Apache 2.0.
