Seed 2.0 Pro vs Step-3.5-Flash

ByteDance

Seed 2.0 Pro is ByteDance's flagship general-purpose model, released in February 2026 under the Doubao brand through the Volcengine API platform, developed by the company's Seed research team as a foundation for agentic applications requiring long-horizon reasoning and multimodal input comprehension. The model accepts text, images, and extended video — including hour-length recordings — targeting enterprise use cases in long-form document analysis, agentic coding (integrated with ByteDance's TRAE IDE), and multi-turn reasoning tasks. It anchors a three-tier product family alongside Seed 2.0 Lite and Mini, positioned as ByteDance's response to frontier model competition in the Chinese and global enterprise AI markets.

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.