What is quantized
NVFP4, group size 16, weights and activations, on the language-model MLP linears only:
model.language_model.layers.{0..63}.mlp.{gate,up,down}_proj
That is 192 quantized linears, 64 layers by three projections. This follows NVIDIA's recipe for dense models rather than quantizing everything reachable.
Kept in BF16:
model.language_model.layers.*.self_attn.*, the 16 full-attention layers
model.language_model.layers.*.linear_attn.*, the 48 Gated-DeltaNet layers
model.visual.*, the entire vision tower
mtp.*, the multi-token-prediction block
lm_head.weight and model.language_model.embed_tokens.weight
- all norms and the Mamba
conv1d weights
KV cache quantization is not enabled, so this checkpoint carries no k_scale or v_scale calibration artifacts.
Recipe
- Tool: NVIDIA ModelOpt 0.45.0
- Stack:
transformers 5.10.1, torch 2.11.0+cu128
- Calibration: 512 samples from
abisee/cnn_dailymail 3.0.0, sequence length 512, max algorithm
- Config:
mtq.NVFP4_DEFAULT_CFG with disable rules appended for *self_attn*, *linear_attn*, *visual*, *vision*, *embed*, *lm_head* and *mtp*
The MTP block
transformers declares _keys_to_ignore_on_load_unexpected = [r"^mtp.*"] for the qwen3_5 architecture, so the MTP weights are dropped silently when the model is loaded and any straightforward export omits them entirely, without raising an error.
The 15 mtp.* tensors here were re-injected unquantized in BF16 after export, written to model-mtp.safetensors and referenced from model.safetensors.index.json. Keep that file alongside the main shards. If it goes missing, downstream tooling will load the model without speculative decoding and give no warning.
Caveats
- Calibration was English news text, matching NVIDIA's published choice. Multilingual and code-heavy workloads were not measured against a held-out set.
- The vision tower is BF16 and was not separately evaluated. Vision quality should track the upstream BF16 release closely.
- This checkpoint was validated by converting it to GGUF and benchmarking there. It has not been tested under vLLM or TensorRT-LLM.
License and attribution
Inherits Apache 2.0 from Qwen/Qwen3.8-27B. All rights, responsibilities and acceptable-use policies of the upstream license apply.
Quantization performed by LibertAI.