Qwen Quietly Changed the Recommended Sampling Parameters for 3.8-27B — Presence Penalty Jumps to 1.5 in Instruct Mode

r/LocalLLaMA (verified against Hugging Face Qwen/Qwen3.8-27B model card)·medium signalXBlueskyLinkedInCopy link

The official Qwen3.8-27B model card specifies different sampling defaults per mode: thinking mode uses temperature 1.0, top-p 0.95, top-k 20, presence penalty 0.0, while instruct/non-thinking uses temperature 0.7, top-p 0.80, top-k 20 and presence penalty 1.5. The r/LocalLLaMA post flagging this drew 59 upvotes and 14 comments, mostly from people who had carried Qwen3.6 configs forward. Anyone reusing a 3.6 serving config will get materially worse output because the presence penalty change is the one setting the identical architecture does not carry over.