It is the default, which is insane.
I think it is clear that medium reasoning has more 'loopy' results like the older Qwens, but I actually think the low effort results are usually more appropriate.
If you plan to one-shot and vibe code AI slop to meet benchmarks, maybe xhigh makes sense. But if you want a responsive agentic coding assistant it is, to me, quite evidently the wrong choice, especially on modest hardware.
I have seen xhigh radically distract itself with rabbitholes and write considerably worse code than low.
It is my own opinion only, but I think much of the fuss about squeezing Qwen 3.8 27B into small local hardware setups, Macs etc., is a bit misguided.
There's too much focus on its benchmark scores, its one-shot capability, canned demos etc.
For my own needs Muse Glimmer (again on reasoning strength: low) is shaping up to being the more practical agentic tool. It is considerably faster than Qwen at solving real coding tasks.