Qwen3.8-Max DSpark speculator

A DSpark speculator for RadixArk/Qwen3.8-2.4T-A95B-NVFP4. DSpark extends the DFlash parallel-draft backbone with a Markov logit-bias head and a per-position confidence head. Trained with SpecForge online distillation from hidden states captured off a live SGLang target engine.

Model specifications

  • Base model: RadixArk/Qwen3.8-2.4T-A95B-NVFP4 (92-layer hybrid-attention MoE, hidden size 8192)
  • Format: single-file BF16 safetensors, 3,298,141,697 parameters
  • Draft: 5 full-attention Qwen3-style GQA layers, hidden size 8192, 64 query heads / 8 KV heads at head_dim 128, block_size=7
  • Verification width: 1 current token + 7 draft tokens
  • Auxiliary target layers: [3, 19, 35, 55, 71, 87], plus the final post-norm hidden state
  • Positional scheme: YaRN factor 32 with original length 8,192 — 262,144 addressable positions, the target's native context limit
  • Target weights: embedding and unembedding weights are not included

Acceptance length

Accept length is the mean number of accepted tokens per verify step including the bonus token (SGLang spec_accept_length), averaged over requests. Setting: SGLang DSPARK serving, TP8 on one 8xB300 node, NVFP4 target, BF16 draft (--speculative-draft-model-quantization unquant), block size 7; sampling temperature 0.6, top_k 20, top_p 0.95, thinking enabled; max_new_tokens 2048; 128 prompts per workload (full set where the dataset is smaller). The measurement loop follows z-lab/dflash benchmark.py.

Workload Accept length Prompts
humaneval 5.30 128
gsm8k 4.89 128
math500 4.85 128
livecodebench 4.72 128
mbpp 4.52 128
aime25 4.43 30
lbpp 4.40 128
aime26 4.35 30
mtbench 3.43 80
arena_hard_v2 3.22 128
alpaca 3.05 128

Serving with SGLang

sglang serve \
  --trust-remote-code \
  --model-path RadixArk/Qwen3.8-2.4T-A95B-NVFP4 \
  --tp-size 8 \
  --speculative-algorithm DSPARK \
  --speculative-draft-model-path RadixArk/Qwen3.8-2.4T-A95B-DSpark \
  --speculative-dspark-block-size 7 \
  --speculative-draft-attention-backend trtllm_mha
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