✅ The first NVFP4 build of any LFM2.5 checkpoint.Checked 2026-08-22: the only other FP4-family
LFM2.5 build is mlx-community/LFM2.5-2.6B-mxfp4, which is MXFP4 for Apple MLX — a different format
and a different runtime. Repository-content comparison only.
This is real W4A4, not weight-only
A weight-only NVFP4 export will not serve: SGLang's _is_fp4a4_nvfp4 returns False when
input_quant is None, and there is no weight-only float4 scheme in the stack. Real W4A4 requires a
calibrated input_global_scale per quantised Linear. This export has them:
Ignore list — the LFM2 hybrid conv path is protected. Quantised: attention projections and
SwiGLU MLPs. Left at bf16: all conv blocks (conv.in_proj / conv.conv / conv.out_proj,
including 3-D kernels), every norm, and the tied embeddings. Quantising recurrent/conv state is the
classic way to destroy this family.
Measured throughput
decode
this NVFP4 build
135.8 t/s
Sample output
/v1/completions, temperature 0, run twice — byte-identical both runs.
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Requirements
Needs a runtime with compressed-tensors NVFP4 W4A4 support on Blackwell —
SGLang v0.5.18-cu130 was used here; vLLM nightly also registers Lfm2ForCausalLM.
llmcompressoroneshot with QuantizationModifier(targets="Linear", scheme="NVFP4") —
notmodel_free_ptq, which cannot calibrate activations and can only emit the unservable
weight-only form. Calibration: HuggingFaceH4/ultrachat_200k (train_sft) via the model's own chat
template. Source revision df58c174f05ff733f83f8cae10ea9298224c8006. Licence inherited from the base model.