Four Open-Weight Models Shipped in 24 Hours. They Defined Three Different Kinds of ‘Open.’

The Date Arrived. The Weights Did Not. On September 20, StepFun committed to releasing the BF16 open weights for its Step-5 model on October 15, 2026. That date has now passed. As of 01:55Z on October 15, the expected HuggingFace repository, stepfun-ai/Step-5-Preview-BF16, returns a 404 error. There is no official repository under the StepFun organization, and while third-party repositories from entities like SHSLab and rene98c have appeared, they remain unendorsed by the lab. The silence from the official @StepFun_ai account on X, which has limited its activity to engagement-only posts, confirms the absence of a release. Metadata BF16 checkpoint weighs in at approximately 1,214.9 GB, requiring at minimum an 8×H100 80GB cluster or 8×B300 equivalent for inference. FP8 and NVFP4 quantized versions are also listed, though the FP8 remains gated.

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