IntelligenceFoundation Models & Infrastructure
StepFun releases 600-billion-parameter Step 5 Preview model
The sparse model ranks among the top open models on the Artificial Analysis index and is due to be open-sourced on Oct. 15.
StepFun released Step 5 Preview on September 20, scoring 44 points on the Artificial Analysis Intelligence Index with a mixture-of-experts model of 600 billion total and 27 billion active parameters.
Why it matters
StepFun's pitch is cost per task, not peak score: an average of $0.71 per Artificial Analysis task, which StepFun puts at one-eighth of Claude Opus 5's, for an open model near the top of the rankings.
The details
- It is a 92-layer Transformer with native text and vision input and a 1-million-token context window.
- API prices are $1 per million input tokens and $2.7 per million output tokens.
- StepFun says it optimised low-level operators and data access so the model's sparsity turns into real throughput.
- Accounts differ on its rank: one puts it second among open models, another third.
The catch
The comparison with Claude Opus 5 is StepFun's own, and the weights are not public until the planned release.