StepFun: Step 3.5 Flash (free)

stepfun/step-3.5-flash:free

Created Jan 29, 2026256,000 context

$0/M input tokens$0/M output tokens

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 (free)

stepfun/step-3.5-flash:free

Created Jan 29, 2026256,000 context

$0/M input tokens$0/M output tokens

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.

Recent activity on Step 3.5 Flash (free)

Total usage per day on OpenRouter

Prompt

2.02B

Reasoning

124M

Completion

38.1M

Prompt tokens measure input size. Reasoning tokens show internal thinking before a response. Completion tokens reflect total output length.