# StepFun teases Step 5 Preview, a 600B/27B MoE, open weights coming Oct 15 > Source: > Published: 2026-09-22 05:06:48+00:00 StepFun on X: "Introducing Step 5 Preview: Advancing the Pareto Frontier. Step 5 Preview is our new flagship model for agentic work, delivering frontier-level performance across software engineering and professional knowledge work, with particular strength in finance. - 600B total / 27B active Mo… / X StepFun on X: "Introducing Step 5 Preview: Advancing the Pareto Frontier. Step 5 Preview is our new flagship model for agentic work, delivering frontier-level performance across software engineering and professional knowledge work, with particular strength in finance. - 600B total / 27B active MoE, with 1M context + Vision - Substantially lower task cost at comparable intelligence - Broad software engineering capabilities with sustained execution over long horizons Try Step 5 Preview: https://t.co/fC7HHlWKFn Model page: https://t.co/4caJR2YGD3 Open weights on Oct 15." Introducing Step 5 Preview: Advancing the Pareto Frontier. Step 5 Preview is our new flagship model for agentic work, delivering frontier-level performance across software engineering and professional knowledge work, with particular strength in finance. - 600B total / 27B active MoE, with 1M context + Vision - Substantially lower task cost at comparable intelligence - Broad software engineering capabilities with sustained execution over long horizons Try Step 5 Preview: platform.stepfun.ai Model page: stepfun.com/step-5-preview Open weights on Oct 15. Introducing Step 5 Preview: Advancing the Pareto Frontier. Step 5 Preview is our new flagship model for agentic work, delivering frontier-level performance across software engineering and professional knowledge work, with particular strength in finance. - 600B total / 27B active MoE, with 1M context + Vision - Substantially lower task cost at comparable intelligence - Broad software engineering capabilities with sustained execution over long horizons Try Step 5 Preview: platform.stepfun.ai Model page: stepfun.com/step-5-preview Open weights on Oct 15. Step 5 Preview works across software environments and sustains execution over long horizons. Its capabilities extend from software engineering and web applications to 3D workflows and programmable hardware. Over longer horizons, Step 5 Preview keeps track of prior results, usesShow more Step 5 Preview is built for professional knowledge work — from large-scale research to structured analysis and interactive reporting. It coordinates research at scale and turns evidence into finished, auditable deliverables. In one agent action, it coordinated 950 web fetchesShow more Finance is a particular focus for Step 5 Preview. Financial work has to stand up to scrutiny. We evaluate Step 5 Preview on its ability to identify and verify reliable information, reconcile differences across reports, make assumptions explicit, and produce internally consistentShow more