StepFun releases Step 3.7 Flash

Background

StepFun (阶跃星辰) is a Chinese AI company whose Step series of models has grown through several releases. Step 3.5 Flash was the model that Step 3.7 Flash builds on. Agents are AI systems that carry out tasks for a user over several steps.

What happened

On 29 May 2026 StepFun released Step 3.7 Flash under the tagline "The new frontier is agent efficiency".^[1] The model extends the Step 3.5 Flash design with image understanding. It has 11 billion active parameters.^[1][2] The weights were released under the Apache 2.0 license.^[2]

StepFun also introduced an Advisor Mode. In this mode the model handles most of a task itself and escalates to a larger model only at key decision points.^[1] This is a design choice that aims to keep the cost of an agent down while still reaching a stronger model when the task needs it.

Key details

StepFun reported 56.3% on SWE-Bench Pro, a harder test of fixing real software issues, and 75.8% on BrowseComp, a test of finding information on the web.^[1]

API pricing was US$0.20 per million input tokens and US$1.15 per million output tokens.^[2] Taken together with the Advisor Mode, the price is one of the figures StepFun used to present the model as efficient. The release tagline and these numbers point to the same emphasis: getting useful agent work done at lower cost.

Impact

For developers who build agents, the combination of open weights, image input and published API prices gives a clear set of options to evaluate. The Advisor Mode splits work between a smaller model and a larger one. The performance numbers are StepFun's own, however, and independent testing would be needed before drawing firm conclusions about how the model compares with others on the same tasks. Several parts of the release can be checked directly against the company's materials: the tagline, the description of the Advisor Mode, and the published API prices. Each of these can be compared with the company's later documentation and with third-party price listings.