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

User reports Qwen3.8-Flash-Next at around 70 t/s for a single session on 4x Radeon AI PRO R9700 32GB. Setup is vLLM with MXFP4-FP8-GPTQ weights, fp8 KV cache, tensor-parallel-size 4, 262144 max model length, and MTP speculative decoding with 3 tokens. The user is troubleshooting a decode performance cap hit with newer vLLM image tags starting from 29.06.19, and notes the BetterBench report incorrectly labels the GPU as RTX 4000 Ada.