Qwen 3.5 397B

Qwen 3.5 397B is Alibaba's flagship reasoning model from the Qwen 3.5 generation, built on a Mixture-of-Experts architecture that totals 397 billion parameters while activating just 17 billion per token. Released in February 2026, it pairs strong chain-of-thought reasoning with broad capability coverage: coding, general knowledge, vision input, native function calling, and web search all sit within a 128,000-token context window. The sparse MoE design is the key trade-off here — it delivers frontier-scale reasoning quality while keeping inference cost closer to a mid-size dense model.

Within Alibaba's lineup it anchors the top of the Qwen 3.5 family, sitting above the lighter Qwen 3.5 35B A3B and Qwen 3.5 9B variants. The line has since continued with Qwen 3.6 27B (released April 2026), so this model represents the heavyweight peak of the prior generation rather than the newest small release. It ships under a permissive Apache 2.0 license, with strong adoption reflected in its Hugging Face download and like counts.

It is best suited for demanding agentic and analytical work — multi-step reasoning, complex code generation, tool-driven workflows, and long-document tasks — where its large expert pool and generous context justify reaching for a flagship over a smaller sibling.

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