Qwen3.8 125B (6B active) Flash-Next

User reports Qwen3.8-Flash-Next prefill at 873 t/s on a 4K prompt on Strix Halo 128GB (Ryzen AI Max+ 395, 96 GB dedicated to the GPU) under native Windows 11. Setup is a Windows port of the Gufo engine on one Strix Halo, UD-Q4_K_XL weights with a Q8_0 MTP head, MTP speculative decoding with survival-based draft stopping and a pruned Latin/code draft vocabulary, 256K context allocated. Decode is reported separately for a summary prompt and a code prompt with no overall figure: 45.3 and 39.7 t/s at empty context, 40.9 and 39.7 at 4K, falling to 38.4 and 37.1 at 158-174K. Prefill stays between 871 and 930 t/s up to 174K. A follow-up turn on a 158K conversation reached first token in 0.4 s from the prompt cache, then 38.6 t/s.