StepFun: Step 3.5 Flash

Developed by stepfun

API Pricing (per 1M tokens)

Input$0.10

Output$0.30

Intelligence Benchmarks

MMLU ProN/A

GPQAN/A

Intelligence IndexN/A

LivebenchN/A

Technical Specifications

Context Window	256K Tokens
Vision Support	No
Tokens per Second	N/A
Time to First Token (s)	N/A
Modalities	text->text

About StepFun: Step 3.5 Flash

Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token. It is a reasoning model that is incredibly speed efficient even at long contexts.

StepFun: Step 3.5 Flash Pricing, API Limits & Benchmarks 2026