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.

• Context window: 262,144 tokens
• Input: text
• Output: text
• Pricing: $0.09/M input tokens, $0.3/M output tokens

View on OpenRouter. Model data sourced from OpenRouter.