Qwen3.8 27B

User reports a custom C + Metal runtime with speculative decoding at 18 t/s end-to-end on coding tasks and 17.7 t/s for an LRUCache implementation, on 36 GB unified memory. Q4 weights are about 15 GB, mmap'd. Prose runs at roughly 10-11 t/s. TTFT is about 1.4s for a short prompt and about 2.7s for a 128-token prompt. The user compares the custom runtime against llama.cpp and reports it faster.