# StepFun launches Step 5 Preview, a 600B-total-parameter agent model

> StepFun says its new flagship for agentic work has 600B total parameters and open weights planned for October 15, 2026. The model targets software engineering, professional knowledge work and finance.

- Publication: Go Big News
- By Nifal Adam, Go Big News Staff (Staff News)
- Category: AI
- Published: 2026-09-21T18:19:17.05+00:00
- Canonical: https://www.gobignews.com/ai/stepfun-launches-step-5-preview-a-600b-total-parameter-agent-model

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[StepFun](https://stepfun.ai) 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](https://platform.stepfun.ai/docs/en/guides/models/step-5-preview) 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.

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## Companies in this story

- Stepfun: https://www.gobignews.com/company/stepfunai

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## X profiles in this story

- @stepfun_ai: https://www.gobignews.com/profile/stepfun_ai