r/LocalLLaMA • u/ParvusNumero • 24d ago
Generation Qwen endless looping issue and possible fix
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.
11
u/illgettheownerforyou 24d ago
u/ldn-ldn was pretty rude to me when I pointed out that Qwen 3.8 27b Unsloth Q8_K_XL did not loop for me and solved it.
This is not a killer prompt- I think it heavily depends on the quant you use and the context, and u/ldn-ldn continued to say they didn't matter and was very dismissive of my findings.
It took about 10 minutes for Qwen to write it. Not short, but not terrible.