Qwen3.8 27B CODER

User reports Qwen3.8-27B CODER decoding at 36-41 t/s on an RX 7900 XTX with 110k-170k tokens already in context. Setup is llama.cpp b11235 on the Vulkan backend with an IQ4_XS imatrix GGUF, q4_1 KV cache, 262144-token context, all layers on the GPU, and MTP speculative decoding from the file's own Q8_0 draft head. Across 98 agentic coding requests the median decode was 41.2 t/s (33.8-46.0) at 65k-131k context and 36.0 t/s (30.7-43.0) at 131k-171k. MTP draft acceptance median 85% (75-94%), about 2.7 tokens per decode step at draft depth 2. Prefill 387 t/s for a cold 108k-token prompt and 175-183 t/s for about 4.5k new tokens at 147k-156k depth. VRAM use 24.2 of 24.6 GB at 245,760 tokens of context, with the vision projector on the CPU.