Demystifying Hybrid Thinking: Can LLMs Truly Switch Between Think and No-Think?

Excerpt

arXiv:2510.12680v2 Announce Type: replace-cross Abstract: Hybrid thinking enables LLMs to switch between reasoning and direct answering, offering a balance between efficiency and reasoning capability. Yet our experiments reveal that current hybrid thinking LLMs only achieve partial mode separation: reasoning behaviors often leak into the no-think mode. To understand and mitigate this, we analyze the factors influencing controllability and identify four that matter most: (1) larger data scale, (2