InternS1 vs Step-3.5-Flash

Shanghai AI Lab

InternS1, released by Shanghai AI Laboratory at WAIC 2025 on July 26, 2025, is a multimodal scientific reasoning large language model designed for advanced problem-solving across mathematics, physics, chemistry, and related domains. It supports text, image, and potentially other scientific data formats as input, and demonstrated strong performance on competition-level scientific benchmarks. InternS1 targets open-source scientific research, STEM education, and applications requiring deep domain reasoning across natural science disciplines.

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.