StepFun unveils open-source Step 5 Preview as Alibaba Cloud announces DAY0 support

StepFun has released its flagship open-source model, Step 5 Preview, to global users, according to a post published on Alibaba Cloud’s official account and cited by ChainCatcher. The model is positioned as a primary work model for real-world agent tasks and is described as being suited to AI coding, software engineering, professional knowledge work, and finance-related use cases. Alibaba Cloud said the model carries 600B total parameters and 27B activated parameters, uses a sparse mixture-of-experts architecture, supports a context window of up to 1M, and can process text, images, and video. The post also said Step 5 Preview recently ranked second globally on OpenRouter’s weekly and daily call-volume charts. On the day of the release, Alibaba Cloud said it completed DAY0 adaptation for the model. The company described a setup built around chip-level support, supernode instances, and joint inference optimization, with inference compute supplied by Lingjun supernodes. The post also outlined sandbox, storage, and security features, including minute-level creation of 30,000 sandboxes, automatic storage expansion from 15GB up to 300GB per Pod, MicroVM-level isolation by default, and support for hundreds of thousands of sandboxes running stably at the same time through ACK One Fleet.