They made a kind of strange decision with Qwen3.8 27B, the template defaults the reasoning_effort to xhigh. I found if you set it to medium it doesn’t just sit there churning forever.
I have seen xhigh go down several rabbit holes, dwell on edge cases and write worse code as a result; it literally distracted itself into writing a complex chain of functions ignoring my prompt, when on “low” reasoning it gets it right on a prompt that requires a few lines of code in the right places.
Simon Willison’s blog has another example (SVG of a circle).
It’s a bit like how giving LLMs access to web search tools can cause them to go down a blind alley based on their first “reasoning” output that then leaves them unable to solve a puzzle correctly that they can fully solve on their own.
With qwen 27b, setting the right reasoning effort for the specific task is important. With xhigh it has a chance at hard problems that bigger models may even fail. But for many everyday tasks, I have found that no reasoning and a system prompt instructing it to be brief is good enough. Note that even with thinking disabled, it may still get into long "chain of thought" reasoning state (out of thinking blocks) if the task is hard and you do not give further instructions, esp with access to tools etc.
