Model Card | Step 5 Preview
Step 5 Preview (StepFun): API launched 2026-09-20, open weights due 2026-10-15; a 600B-total, 27B-active sparse MoE with a 92-layer narrow-deep Transformer, 1M-token context, and text/image/video input; API pricing is $1.00 input (cache hit $0.05) / $2.70 output per 1M tokens; scores 44 on the independent Artificial Analysis Intelligence Index, on par with Kimi K3 and Grok 4.6 but behind Claude Opus 5 (51) and the tied GPT-6 Astra / Claude Fable 5.1 (53); its cost per task runs about 42% below Gemini 3.8 Flash at a comparable score; for agent development it's a mid-tier option offering near-frontier intelligence at a fraction of the cost, suited to long-horizon research agents and financial analysis