StepFun launches Step 5 Preview, a 600B-parameter MoE agent model with 1M context
Open weights promised for Oct 15
Confirmed
The takeaway
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.
Status
- Claim
Confirmed
- Our reporting
- High confidence
- Importance
- 3 of 5
- Last verified
- 15 October 2026
Your AI and this story
- GPT-6 Astra143 days after its cutoff
- Claude Opus 5.582 days after its cutoff
- Gemini 4 Hydrogen173 days after its cutoff
- Grok 4.7112 days after its cutoff
None of these four assistants can know about it. The closest, Claude Opus 5.5, stops 82 days before it.
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
- Oct 12, 2026: StepFun announced that Step 5 Preview is available in Tencent’s WorkBuddy office agent, free from Oct 12 to Oct 25 in an arrangement StepFun calls exclusive (Pandaily, citing IT Home); no word on pricing after the window or whether the model stays in WorkBuddy
- StepFun’s own pricing page (read Oct 13, 2026) lists the cache-hit input price at $0.10 per 1M tokens, not the $0.05 reported at launch; $1.00 input and $2.70 output are unchanged
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.
Sources
5 sources from 3 sites. Numbers match the chips in the text.
5 sources: 2 primary, 3 press
Primary
- StepFun docs: Pricing and Rate Limitsplatform.stepfun.ai, docs
- StepFun docs: Step 5 Previewplatform.stepfun.ai, docs
Press
- MarkTechPost: StepFun launches Step 5 Previewmarktechpost.com, press
- Pandaily: StepFun Step 5 Preview, 600B MoE, open weights Oct 15pandaily.com, press
- Pandaily: StepFun’s Step 5 Preview Comes to Tencent WorkBuddy, Free to Use Exclusively Until October 25pandaily.com, press
Changes
- Weights released on time (see
[StepFun releases Step 5 Preview open weights](/e/2026-10-15-stepfun-step-5-preview-open-weights/)) - Read Pandaily’s article for the WorkBuddy details; cache-hit price checked on StepFun’s pricing page ($0.10)
- Added the Tencent WorkBuddy free-access window, from Pandaily’s headline
- Filed