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

User reports Qwen3.8 Flash-Next at 39.8 t/s mean decode on two DGX Sparks, with final code decode at roughly 74 t/s mean. Setup is vLLM with FP8 weights and NVFP4 KV cache, TP=2 across two DGX Sparks, DSpark speculative decoding with 3 proposed tokens, single concurrency. User also tried DeepSeek V4 Flash on the same setup but it failed benchmarks due to non-completion and excessive token use (30-45k tokens on an easy task), unlike cloud versions of the same model. User is happy with Qwen3.8 Flash-Next but concerned about overthinking tendency.