StepFun: Step 3.5 Flash

STEPFUN Developer Architecture Profile

Intelligence (ELO)1150Chatbot Arena Verified

Max Context256,000Tokens

API Cost / 1M$0.40Blended Prompt + Completion

Model Capabilities

Drafting
Classification

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.

Granular Pricing Matrix

Input Tokens (Prompt)$0.10 / 1M

Output Tokens (Completion)$0.30 / 1M

Pricing data via OpenRouter. Sync: 3/16/2026

Evaluate Competitors

VS Engine MatchupStepFun: Step 3.5 Flash vs ByteDance Seed: Seed-2.0-Lite VS Engine MatchupStepFun: Step 3.5 Flash vs Qwen: Qwen3.5-35B-A3B VS Engine MatchupStepFun: Step 3.5 Flash vs Qwen: Qwen3.5-Flash VS Engine MatchupStepFun: Step 3.5 Flash vs MiniMax: MiniMax M2.5 (free)VS Engine MatchupStepFun: Step 3.5 Flash vs MiniMax: MiniMax M2.5 VS Engine MatchupStepFun: Step 3.5 Flash vs StepFun: Step 3.5 Flash (free)