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Overview
Step 5 Preview is stepfun’s September 2026 flagship sparse MoE model — 600B total parameters, 27B active per token, 1M context window, vision input, and agentic software-engineering focus.
Recent Developments
- 2026-09-20: API live; Artificial Analysis Intelligence Index score 44; pricing 2.70 per M input/output tokens; open weights planned Oct 15, 2026 (2026-09-20-stepfun-step-5-preview)
Benchmark scores and capability claims are vendor/Artificial Analysis reported — independent replication pending.