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Step 3.7 Flash

Step 3.7 Flash is StepFun's flagship multimodal reasoning model, a sparse MoE with 11B active parameters and native image and video understanding. It supports a context window of 256K tokens and a max output of 256K tokens per request.

Implicit CachingReasoningTool UseVision (Image)
index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'stepfun/step-3.7-flash',
  prompt: 'Why is the sky blue?'
})
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About Step 3.7 Flash

Released on May 28, 2026, Step 3.7 Flash is StepFun's flagship multimodal reasoning model. The architecture pairs the sparse mixture-of-experts language backbone from step-3.5-flash with a dedicated vision encoder, for roughly 198B total parameters and 11B active per token. Weights are published on GitHub, Hugging Face, and ModelScope.

Vision is built for action, not just description. Step 3.7 Flash reads product UIs, documents, charts, spreadsheets, and natural scenes, then writes code or calls tools based on what it sees. A built-in Python tool lets Step 3.7 Flash crop, zoom, and annotate images mid-task, and visual search extends coverage to long-tail entities. That composition shows up in the numbers: 95.29% on V* with Python tooling and 89.13% on HR-Bench 4K.

Agentic performance improves alongside the new modality. Step 3.7 Flash scores 76.5% on SWE-Bench Verified, 56.3% on SWE-Bench Pro, and 59.5% on Terminal-Bench 2.1, gaining about five points on SWE-Bench Pro and six points on Terminal-Bench 2.1 over step-3.5-flash. On search and research tasks, Step 3.7 Flash posts 75.82% on BrowseComp and 47.2% on Humanity's Last Exam with tools. StepFun trained the model to treat search as part of reasoning, favoring search planning and evidence filtering over memorized knowledge.

Through AI Gateway, you call Step 3.7 Flash with one API key and get provider routing, automatic failover, and built-in observability. Integrate via the AI SDK, the Chat Completions API, the Responses API, the Messages API, or other supported API formats.