Qwen3.5 9B

User reports Qwen3.5 9B Q4_K_M decoding at 7.89 t/s on an AMD RX 9070 XT under a pinned llama.cpp Vulkan build (b10964), while LM Studio's Vulkan llama.cpp build reaches 29.89-30.46 t/s on the same GPU and byte-identical GGUF. Setup is llama.cpp with Q4_K_M and q8_0 KV cache at 32768 context, flash attention on, single RX 9070 XT; llama-bench -p 128 -n 64 -r 1 gives 451.45 pp128 t/s and 7.89 tg64 t/s at -ngl 99. -ngl 0 (CPU) decodes at 8.00 t/s and -ngl 99 at 7.83-7.89 t/s, so GPU offload buys nothing; the iGPU alone gives 3.04 t/s. Through the managed runtime decode is 7.41-7.49 t/s with prompt eval 98-222 t/s. LM Studio loaded the model at 255744 context and was still about 4x faster. Root cause not established.