StepFun Ships Step 5 Preview API, a 600B MoE at $1/$2.70 That Scores 44 on Intelligence Index

StepFun officially announced Step 5 Preview on September 20, a 600B-parameter sparse MoE with 27B active per token and a 1M-token context, and opened API access the same day. Artificial Analysis pegs the model at 44 on its Intelligence Index — matching Kimi K3 Max and roughly a seventh the price of GPT-5.6 Sol — at $1 per million input tokens and $2.70 per million output tokens with a 95% cache discount. StepFun says full open weights follow on October 15; the Hugging Face repo currently ships only a .gitattributes file.