StepFun launches Step 5 Preview, a 600B-parameter MoE agent model with 1M context; open weights promised for Oct 15
On Sept 20, 2026 StepFun released Step 5 Preview (`step-5-preview`), its flagship agentic model: a 600B total / 27B active sparse MoE with 92 layers, a 1M-token context and 64K max output, taking text, up to 60 images and video. It costs $1.00 input ($0.05 cached) and $2.70 output per 1M tokens and reportedly scores 44 on the Artificial Analysis index. StepFun promises open weights on Oct 15.
Key facts
- Released Sept 20, 2026; model id step-5-preview
- 600B total / 27B active MoE, 92 layers (narrow-deep design)
- Context 1M tokens; max output 64K; input text, up to 60 images, video (MP4 <128 MB)
- Pricing per 1M tokens: $1.00 input (cache miss), $0.05 (cache hit), $2.70 output
- Company/press-reported: AA Intelligence Index 44, FrontierFinance 66.4, DRACO 83.3, DeepSWE v1.1 67.7
- Open weights promised for Oct 15, 2026 (HF placeholder stepfun-ai/Step-5-Preview-BF16); license not yet stated
What happened
StepFun joined the 1M-context agent-model tier with a sparse MoE aimed at software engineering and finance work.
Why it matters
It adds another Chinese open-weights candidate near frontier-lab mid-tier scores. Check on Oct 15 whether the weights and license were released.
Changelog
- 2026-09-29: created
Models
- Step 5 Preview StepFun · preview
Related events
Sources (3)
- docsStepFun docs: Step 5 Preview
- pressMarkTechPost: StepFun launches Step 5 Preview
- pressPandaily: StepFun Step 5 Preview, 600B MoE, open weights Oct 15
id: 2026-09-20-stepfun-step-5-preview · updated 2026-09-29 · open in the interactive timeline