StepFun opens Step 5 Preview weights: 600B MoE, 27B active, 1M context

StepFun released Step 5 Preview as open weights: 600B-parameter MoE, 27B active per token, 1M-token context. FP8 runs on 4x B300 GPUs; the API costs $1.00/$2.70 per 1M tokens.