Qwen3.5 Still Performs Extended Reasoning Even When Thinking Mode is Disabled

_lewtun · x · 2026-07-30

Hugging Face engineer Lewis Tunnicliffe noticed that when evaluating Qwen3.5 models with enablethinking=false, the models still exhibit a form of extended reasoning, generating "Wait, ..." or even <think> tags. This is particularly evident in out-of-domain evaluations (e.g., biology), resulting in massive token generation. In contrast, Gemma4 models strictly follow the setting and produce concise outputs, raising questions about their differing post-training recipes.

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