> In particular, Qwen3.5-Plus is the hosted version corresponding to Qwen3.5-397B-A17B with more production features, e.g., 1M context length by default, official built-in tools, and adaptive tool use. For more information, please refer to the User Guide.

https://huggingface.co/Qwen/Qwen3.5-397B-A17B

So 3.5-plus has been released as open weights.