# StepFun: what I've logged

> StepFun comes up in 3 posts of my AI log, from February 2026 to September 2026, and each item below links to the primary source. The releases I logged include Step 5 Preview, Step 3.7 Flash and Step 3.5 Flash, filed under frontier, image, video, world and open weights.

## Items

1. **Step 5 Preview** (StepFun, 14 Sept 2026): A 600B mixture-of-experts model with 27B active parameters and a 1M-token window, aimed at agentic software and finance work. [Primary source](https://www.stepfun.com/step-5-preview) · [Post](https://heyaliasif.com/ai/2026-09-14-week-in-ai#item-2)
2. **Step 3.7 Flash** (StepFun, 25 May 2026): StepFun's May 28 release, with a model page on Hugging Face. [Primary source](https://huggingface.co/stepfun-ai/Step-3.7-Flash) · [Post](https://heyaliasif.com/ai/2026-05-25-week-in-ai#item-4)
3. **Step 3.5 Flash** (StepFun, 2 Feb 2026): StepFun's fast open reasoning and agent model. [Primary source](https://huggingface.co/stepfun-ai/Step-3.5-Flash) · [Post](https://heyaliasif.com/ai/2026-02-02-week-in-ai#item-4)

## Posts

- 2026-09-14 [Gemini 3.8 Live, open Qwen-Image-2.1 and Anthropic's Accenture pact](https://heyaliasif.com/ai/2026-09-14-week-in-ai)
- 2026-05-25 [Claude Opus 4.8, NVIDIA's Cosmos 3 keynote, Codex on Windows](https://heyaliasif.com/ai/2026-05-25-week-in-ai)
- 2026-02-02 [Claude Opus 4.6 and GPT-5.3-Codex land on the same day](https://heyaliasif.com/ai/2026-02-02-week-in-ai)

Canonical: https://heyaliasif.com/ai/topics/stepfun