StepFun Step 3.5 Flash Is Now Available in Puter.js
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Puter.js now supports Step 3.5 Flash, StepFun's open-source foundation model engineered for frontier reasoning and agentic capabilities with exceptional efficiency.
What is Step 3.5 Flash?
Step 3.5 Flash is a sparse Mixture-of-Experts (MoE) large language model with 196B total parameters, activating only 11B per token. This architecture delivers the reasoning depth of top-tier models while maintaining real-time responsiveness with inference speeds of 100-350 tokens per second.
The model features a 256K context window and excels at agentic tasks, mathematical reasoning, coding, and deep research. It achieves impressive benchmark scores including 97.3 on AIME 2025, 74.4% on SWE-bench Verified, and 86.4% on LiveCodeBench-V6.
Examples
Mathematical Reasoning
puter.ai.chat(`Solve this step by step: A farmer has 17 sheep.
All but 9 run away. How many sheep does the farmer have left?`, {
model: "stepfun/step-3.5-flash:free"
})
Agentic Code Generation
puter.ai.chat(`Design a Python script that automatically monitors
a directory for new files, processes them based on file type,
and generates a summary report`, {
model: "stepfun/step-3.5-flash:free"
})
Get Started Now
Just add one script tag to your HTML:
<script src="https://js.puter.com/v2/"></script>
No API keys or account needed. Start building with Step 3.5 Flash's ultra-fast agentic capabilities immediately.
Learn more:
Free, Serverless AI and Cloud
Start creating powerful web applications with Puter.js in seconds!
Get Started Now