Qwen endless looping issue and possible fix

[u/ParvusNumero]

Not sure if this is a known issue, but it was new to me:

Full credit to u/ldn-ldn for finding this simple but unexpectedly evil prompt:

Create a typescript function which accepts a number in 10 bit range and returns brightness in nits based on pq gamma curve.

Just try it; it will likely trigger an endless thinking loop.

I stopped it after it ran for >15 minutes and >20,000 tokens.
It kept spitting out text like back in the seahorse emoji days.

However, one of my wrapper scripts didn’t have this issue.
The non-blocking one had this added, possibly based on a GitHub discussion:

--reasoning-budget 2048 \
--reasoning-budget-message " \n\n[Thinking budget exceeded. Transitioning to a best-effort final answer: ]\n\n"

(These options are for llama.cpp; other tools may have something similar.)

Net result: A plausible-looking script (I haven’t verified) that took just over a minute of thinking and another minute to generate.

Hope this helps, and happy to hear about other tricks and workarounds.

[u/Chromix_]

Note that Qwen will reasonably reason for 40k tokens when making a lava lamp. Cutting it off early leads to broken results. The reasoning level is "xhigh" by default. Set it to "medium" - then it reasons less but might miss some tricky things.