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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.

From 3 Chinese-language reportsAIPressRoom Intelligence

Illustration: AIPressRoom

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.

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.