StepFun launches Step 5 Preview: 600B/27B MoE agent flagship, open weights Oct 15

Why it matters

StepFun announced Step 5 Preview as its flagship for agentic work—software engineering and professional knowledge work, with a finance focus. Claimed specs: 600B total / 27B active MoE, 1M context, vision (text/image/video), lower task cost at comparable intelligence, and long-horizon runs (up to 24h in tests). Platform API id step-5-preview is available now; open weights planned Oct 15. Official model page and docs linked in the announcement.