StepFun releases open weights for Step 5 Preview with 600B parameters

StepFun published Step 5 Preview weights on Hugging Face on October 15 in FP8, BF16 and NVFP4 formats under the StepFun Model License 1.0. The sparse MoE model has 600B total parameters with 27B active per token, a 1M-token context and API pricing of $1/$2.70 per 1M input/output tokens.

• 600B total parameters, 27B active per token (about 4.5%)
• 1M-token context window; text and image input
• API pricing: $1 per 1M input and $2.70 per 1M output tokens
• Nvidia claims ~8,000 tokens/sec per GPU on GB300 in NVFP4