A.I.
Rycode

Jeffrey 1 min read

Open weight · stub

Step 5 Preview (StepFun)

Step 5 Preview is StepFun’s flagship agentic model. The product page positions it for software engineering and professional knowledge work, with a noted lean toward finance. It is available through StepFun products and API. Downloadable open weights are scheduled for 15 October 2026, not yet public on this card’s research date (22 Sep 2026 ET).

Status
Preview, open weights scheduled for 15 Oct 2026
AA score
44Artificial Analysis Intelligence Index, one independent score across many tests, fetched 22 Sep 2026
Last checked
22 Sep 2026newest source date on this page

On the Artificial Analysis Intelligence Index (fetched 22 Sep 2026 ET), Step 5 Preview scores 44.

What is published

From StepFun’s Step 5 Preview materials (product page):

  • Sparse Mixture-of-Experts
  • 600B total parameters, 27B active per token
  • 1M-token context window
  • Vision input supported
  • API and Studio access open; open weights dated 15 Oct 2026

What is still missing for a full learning card

Until weights and a complete model card land:

  • Final license text for the open release
  • Confirmed Hugging Face artifact listing (weights, configs, serving notes)
  • Lab-primary system card or tech report depth comparable to Kimi / GLM / MiMo cards
  • Whether preview API behavior matches the eventual open checkpoint one-for-one

This page stays a short stub until those primaries exist. The only size figures here are the ones StepFun published. Third-party price blogs are not used.

Benchmarking

AA Index: 44 (leaderboard, 22 Sep 2026 ET). Lab harness tables should be cited from StepFun when published; they are not copied from secondary blogs here.

Access

Sources