AI model · StepFun
Step 3.5 Flash
Model ID: stepfun/step-3.5-flash
- Input
- $0.10 per 1M tokens
- Output
- $0.30 per 1M tokens
- Context
- 262K tokens at once
- Max output
- 66K tokens per reply
- Released
- 29 Jan 2026 StepFun
What it can do
- YesReasoning
- YesTool calling
- NoImage input
- YesOpen weights
- NoFree to use
Takes text; gives text.
How its listing describes it
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....
Sources
- StepFun: Step 3.5 Flash on OpenRouter — read 2 Oct 2026