Qwen3.5 is the latest large language model series developed by Alibaba Cloud's Qwen team, featuring a groundbreaking 397B-parameter Mixture-of-Experts architecture. Released on February 16, 2026, it introduces a hybrid attention mechanism combining quadratic and linear attention heads, support for 201 languages and dialects, and unified multimodal capabilities through early fusion training. The flagship Qwen3.5-397B-A17B model activates only 17B parameters per forward pass, delivering 60% lower operational costs and 8x throughput improvements over its predecessor while matching top-tier models from OpenAI, Anthropic, and Google on major benchmarks.