DFlash Qwen3.5-27B Uncensored

27B hybrid linear-attention model | BF16 full-precision | Vision + Text | DFlash speculative decoding

Performance (DGX Spark GB10, NVFP4 version)

Quick Links

Quick Start (DGX Spark)

1. Download the model

huggingface-cli download AEON-7/DFlash-Qwen3.5-27B-Uncensored \
  --local-dir ~/models/DFlash-Qwen3.5-27B-Uncensored

2. Create your environment file

# Auto-generate API key and create .env
cat > .env.dflash << 'EOF'
# Authentication
HF_TOKEN=hf_your_token_here
VLLM_API_KEY=$(openssl rand -hex 32)

# Model path
MODEL_HOST_PATH=~/models/DFlash-Qwen3.5-27B-Uncensored

# DFlash speculative decoding (auto-downloads drafter on first run)
DFLASH_DRAFTER=z-lab/Qwen3.5-27B-DFlash
DFLASH_NUM_SPEC_TOKENS=15

# DGX Spark optimal settings (BF16, 64K context)
MAX_MODEL_LEN=65536
MAX_NUM_SEQS=2
GPU_MEMORY_UTILIZATION=0.90
MAX_NUM_BATCHED_TOKENS=65536
EOF

# Generate a real API key and inject it
sed -i "s|\$(openssl rand -hex 32)|$(openssl rand -hex 32)|" .env.dflash
echo "Your API key: $(grep VLLM_API_KEY .env.dflash | cut -d= -f2)"

3. Save docker-compose.dflash-bf16.yml

services:
  vllm-dflash-bf16:
    image: ghcr.io/aeon-7/vllm-dflash:latest
    container_name: vllm-dflash-bf16
    restart: unless-stopped
    network_mode: host
    ipc: host
    volumes:
      - ${MODEL_HOST_PATH}:/models/DFlash-Qwen3.5-27B-Uncensored
      - dflash-drafter-cache:/models/drafter-cache
    environment:
      - MODEL_PATH=/models/DFlash-Qwen3.5-27B-Uncensored
      - SERVED_MODEL_NAME=DFlash-Qwen3.5-27B-Uncensored
      - DFLASH_DRAFTER=${DFLASH_DRAFTER}
      - DFLASH_NUM_SPEC_TOKENS=${DFLASH_NUM_SPEC_TOKENS}
      - GPU_MEMORY_UTILIZATION=${GPU_MEMORY_UTILIZATION}
      - MAX_MODEL_LEN=${MAX_MODEL_LEN}
      - MAX_NUM_SEQS=${MAX_NUM_SEQS}
      - MAX_NUM_BATCHED_TOKENS=${MAX_NUM_BATCHED_TOKENS}
      - NVIDIA_VISIBLE_DEVICES=all
      - TORCH_MATMUL_PRECISION=high
      - PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True
      - HF_TOKEN=${HF_TOKEN}
      - VLLM_API_KEY=${VLLM_API_KEY}
    deploy:
      resources:
        reservations:
          devices:
            - driver: nvidia
              count: all
              capabilities: [gpu]

volumes:
  dflash-drafter-cache:

4. Launch

docker compose --env-file .env.dflash -f docker-compose.dflash-bf16.yml up -d

# Watch startup (~5-8 min for weight loading + compilation)
docker compose -f docker-compose.dflash-bf16.yml logs -f

5. Test

# Text generation
curl http://localhost:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $(grep VLLM_API_KEY .env.dflash | cut -d= -f2)" \
  -d '{
    "model": "DFlash-Qwen3.5-27B-Uncensored",
    "messages": [{"role": "user", "content": "Explain quantum entanglement simply."}],
    "max_tokens": 200
  }'

# Vision (image understanding)
curl http://localhost:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $(grep VLLM_API_KEY .env.dflash | cut -d= -f2)" \
  -d '{
    "model": "DFlash-Qwen3.5-27B-Uncensored",
    "messages": [{"role": "user", "content": [
      {"type": "image_url", "image_url": {"url": "https://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Cat03.jpg/1200px-Cat03.jpg"}},
      {"type": "text", "text": "What do you see?"}
    ]}],
    "max_tokens": 200
  }'

Environment Variables

Why This Model

Why Dense Over MoE

Qwen3.5 comes in two flavors: the 122B-A10B MoE (256 experts, 10B active per token) and this 27B dense model (all parameters active on every token). The dense model has real advantages:

• Higher quality per FLOP — Every one of the 27B parameters contributes to every token. MoE models route to a sparse subset, which means some experts are undertrained and routing decisions introduce noise. Dense models don't have this problem.
• No routing overhead — MoE models spend compute on expert selection, load balancing, and all-to-all communication. Dense models just run the computation.
• Predictable latency — No variance from different experts being selected per token. Every forward pass costs the same.
• Simpler deployment — No expert parallelism concerns, no load imbalance, fits on a single GPU with NVFP4.

The tradeoff has always been speed: a 27B dense model moves 27B parameters through memory per token, while the 122B MoE only moves ~10B active parameters. On a memory-bandwidth-limited device like DGX Spark (273 GB/s), that meant the dense model was slow — 12 tok/s baseline.

DFlash changes this equation entirely. See below.

Why DFlash Makes Dense Practical on DGX Spark

The fundamental bottleneck on DGX Spark is memory bandwidth. At 273 GB/s, loading 20 GB of NVFP4 weights per token limits you to ~12 tok/s. Every dense model hits this wall.

DFlash block-diffusion speculative decoding breaks through it:

1. The 2B drafter proposes multiple tokens simultaneously — one diffusion forward pass generates an entire block of speculative tokens in parallel, not sequentially. This costs roughly the same as generating a single token.
2. The 27B target verifies all proposed tokens in one forward pass — instead of paying the full memory bandwidth cost per token, you pay it once and produce 3-4 accepted tokens on average.
3. Net effect: you amortize the bandwidth cost across multiple tokens per forward pass.

The result on DGX Spark:

This makes the 27B dense model faster than the 122B MoE on a single DGX Spark while delivering the quality advantages of a dense architecture. DFlash turns the DGX Spark from "it can run a 27B model" into "it runs a 27B model well."

Hybrid Architecture

Qwen3.5-27B uses a hybrid architecture mixing two attention types across 64 layers:

• Linear attention (GDN) — Gated Delta Network layers for efficient long-context processing with O(1) per-token state (48 layers)
• Full attention — Standard multi-head attention every 4th layer for global context capture (16 layers)

This gives near-linear scaling with sequence length while maintaining full-attention quality at key intervals.

Vision + Text

Includes a 27-layer ViT vision encoder (460M params) with a merger that projects visual features into the language model's hidden space. Supports image understanding alongside text generation.

DFlash Block-Diffusion Speculative Decoding

Pair with z-lab/Qwen3.5-27B-DFlash — a 2B block-diffusion drafter that generates all speculative tokens simultaneously in a single diffusion step. The container auto-downloads and configures this.

Abliteration

Created using the orthogonal projection abliteration technique:

1. Measures refusal directions across harmful/harmless prompt pairs
2. Analyzes layer-by-layer activation patterns to identify the refusal direction
3. Abliterates by projecting out the refusal direction from weight matrices

Modifies weights directly (not LoRA/adapter). Standalone BF16 model with no built-in refusal behavior.

Model Details

Why NVFP4 on Blackwell

If you have an NVIDIA Blackwell GPU (B200, GB200, GB10/DGX Spark, or later), you should use the NVFP4 version instead. Here's why:

NVFP4 is effectively lossless on Blackwell. The FP4 (E2M1) format is a native tensor core datatype on Blackwell's SM 12.x architecture. Unlike older INT4/GPTQ quantization that introduces significant degradation, NVFP4 with AWQ_FULL calibration preserves model quality while giving you:

• 3x memory reduction — 20 GB vs 52 GB, freeing memory for longer context and more concurrent requests
• Hardware-accelerated FP4 GEMM — Blackwell tensor cores execute FP4 matrix multiplies natively via FlashInfer CUTLASS, not through dequantize-then-compute
• Higher throughput — The smaller weight footprint means less memory bandwidth consumed per token, directly translating to faster inference
• Same quality — AWQ_FULL uses exhaustive grid search (10 scaling factors per layer) plus clipping optimization. The vision encoder, embeddings, norms, and lm_head remain in full BF16

This is a free performance boost — you get the same model quality at 3x less memory and measurably faster inference. The BF16 version here is primarily for non-Blackwell hardware or research workflows that need full-precision weights.

Alternative Deployment

vLLM (Manual)

vllm serve AEON-7/DFlash-Qwen3.5-27B-Uncensored \
  --speculative-config '{"method": "dflash", "model": "z-lab/Qwen3.5-27B-DFlash", "num_speculative_tokens": 15}' \
  --attention-backend flash_attn \
  --kv-cache-dtype auto \
  --gpu-memory-utilization 0.85 \
  --max-num-batched-tokens 8192 \
  --max-num-seqs 4 \
  --enable-chunked-prefill \
  --enable-prefix-caching \
  --trust-remote-code

Transformers

from transformers import AutoModelForCausalLM, AutoTokenizer

model_name = "AEON-7/DFlash-Qwen3.5-27B-Uncensored"
tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(
    model_name, torch_dtype="auto", device_map="auto"
)

messages = [{"role": "user", "content": "Hello, tell me about yourself."}]
text = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer([text], return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=512)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))

Credits

• Base model by Qwen Team
• DFlash speculative decoding by z-lab (paper)
• Abliteration using llm-abliteration
• Release by AEON-7

Legal Disclaimer

THIS MODEL IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. This model has had safety alignment removed. Users are responsible for ensuring ethical and legal use.

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