Claude 3.7 Sonnet vs Step-3.5-Flash

Claude 3.7 Sonnet

Anthropic

Claude Sonnet 3.7, released by Anthropic in February 2025, is a large language model from the Claude 3 family featuring hybrid reasoning with configurable extended thinking. It supports a 200K token context window, 64K maximum output tokens (128K in beta), and native image understanding. Sonnet 3.7 targets complex coding, mathematics, and scientific reasoning tasks where extended chain-of-thought processing provides meaningful improvements in output quality.

StepFun

Step-3.5-Flash, released by StepFun on February 2, 2026, is a Mixture-of-Experts large language model with 197 billion total parameters and approximately 11 billion active parameters per inference. It features a 256K token context window using a 3:1 sliding-window-to-full-attention ratio, processing 100–350 tokens per second. Step-3.5-Flash targets agentic tasks, coding workflows, and open-source deployments requiring frontier reasoning capabilities with efficient inference, under an Apache 2.0 license.