Qwen3.5 4B

User reports Qwen3.5-4B at 10.61 t/s decode on a Rockchip RK3588 NPU with the open_rknpu2_lm_infer engine, using MTP speculative decoding. Setup is a custom Rust/C++ runtime that avoids Rockchip's proprietary inference libraries, with an OpenAI-compatible API, streaming, tool calling and prefix caching; prefill of a 512-token prompt ran at 147.83 tok/s. User compares against RKLLM 1.3.1, which reached 5.54 tok/s decode after 512 tokens and 58.35 tok/s prefill; decode after 3,800 tokens was 9.90 tok/s versus 4.57 tok/s.