---
id: "2026-09-20-stepfun-step-5-preview"
url: "https://postcutoff.com/e/2026-09-20-stepfun-step-5-preview/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2026-09-20"
date_precision: day
category: model-release
importance: 3
confidence: high
status: [Confirmed]
sources: 5
editor: human editor
human_review: null
version: "2026-10-15"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-09-20-stepfun-step-5-preview/

# StepFun launches Step 5 Preview, a 600B-parameter MoE agent model with 1M context

Full title: 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
- 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.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): 143 days after its cutoff
- Claude Opus 5.5 (training cutoff June 2026): 82 days after its cutoff
- Gemini 4 Hydrogen (training cutoff March 2026): 173 days after its cutoff
- Grok 4.7 (training cutoff May 2026): 112 days after its cutoff

## Sources

1. [StepFun docs: Pricing and Rate Limits](https://platform.stepfun.ai/docs/en/guides/pricing/details) (platform.stepfun.ai, docs)
2. [StepFun docs: Step 5 Preview](https://platform.stepfun.ai/docs/en/guides/models/step-5-preview) (platform.stepfun.ai, docs)
3. [MarkTechPost: StepFun launches Step 5 Preview](https://www.marktechpost.com/2026/09/20/stepfun-launches-step-5-preview/) (marktechpost.com, press)
4. [Pandaily: StepFun Step 5 Preview, 600B MoE, open weights Oct 15](https://pandaily.com/stepfun-step-5-preview-600b-moe-1m-context-open-weights-oct-15) (pandaily.com, press)
5. [Pandaily: StepFun's Step 5 Preview Comes to Tencent WorkBuddy, Free to Use Exclusively Until October 25](https://pandaily.com/stepfun-step-5-preview-tencent-workbuddy-exclusive-free-access-oct-12-25) (pandaily.com, press)

## Changes

- 2026-10-15: Weights released on time (see `[StepFun releases Step 5 Preview open weights](https://postcutoff.com/e/2026-10-15-stepfun-step-5-preview-open-weights/)`)
- 2026-10-13: Read Pandaily's article for the WorkBuddy details; cache-hit price checked on StepFun's pricing page ($0.10)
- 2026-10-13: Added the Tencent WorkBuddy free-access window, from Pandaily's headline
- 2026-09-29 (filed): Created

## Related

- 2026-10-15: [StepFun releases Step 5 Preview open weights](https://postcutoff.com/e/2026-10-15-stepfun-step-5-preview-open-weights/index.md)
- 2026-09-15: [StepFun releases StepAudio 3 family](https://postcutoff.com/e/2026-09-15-stepfun-stepaudio-3/index.md)
- Models: [Step 5 Preview](https://postcutoff.com/m/step-5-preview/) (`step-5-preview`)