LFM3-1.7B NVFP4 (Schur Replay)

LFM3-1.7B NVFP4

Modified weights notice: this repo contains a quantized (NVFP4) derivative of LiquidAI/LFM3-1.7B. The feed-forward weights were re-quantized by BennyDaBall; everything else is Liquid AI's original BF16. Not affiliated with or endorsed by Liquid AI.

Same layer map, same file format and same speed as Liquid's official LFM3-1.7B-NVFP4. Better 4-bit weights: 1.36x closer to BF16 under W4A4, 1.87x on the weights alone. For llama.cpp / LM Studio, see the GGUF twin: BennyDaBall/LFM3-1.7B-NVFP4-GGUF (1.28 GB, 2.03x closer to BF16 than a converted Liquid NVFP4, runs on stock llama.cpp).

What changed vs Liquid's NVFP4

Liquid NVFP4 This repo
Layer map NVFP4 W4A4 on language feed-forward weights + activations; attention, convs, embeddings, head, norms BF16 Identical (Liquid's map, cited from their card)
Weight solver Round-to-nearest (ModelOpt default; we checked: weight error identical to plain RTN) GPTQ + Schur Replay block-scale selection + Four Over Six
Activations Static per-tensor input_scale, dynamic per-16 block scales Same scheme, recalibrated on our set
Format ModelOpt NVFP4 safetensors Same (drop-in)

Schur Replay (arXiv 2609.36654): inside the GPTQ loop, each 16-weight block tries a window of E4M3 scale codes plus the Four Over Six map-to-4 scale (arXiv 2512.02010). Every candidate replays the block's GPTQ updates and is scored by its real GPTQ loss (the Schur complement of the not-yet-quantized columns). Each row keeps its best. Hessians come from 599k calibration tokens (tool calls, chat, reasoning, raw text). The chat, tool-call and reasoning answers are the BF16 model's own generations.

KLD vs BF16 (lower is better)

Gold = LiquidAI/LFM3-1.7B BF16 (transformers). Held-out eval: 150 sequences, 124,790 scored tokens (every model-written span: tool calls, chat, reasoning, plus raw text). NVFP4 math reproduced exactly as the W4A4 kernels compute it.

W4A4 (vLLM / SGLang path) Mean KLD Median p99 Top-1 agree Tool Chat Reasoning Raw
Liquid NVFP4 0.0628 0.0187 0.584 90.3% 0.0353 0.0707 0.0378 0.0870
This repo 0.0461 0.0133 0.441 91.6% 0.0233 0.0523 0.0262 0.0663
Weight-only view (W4A16) Mean KLD Top-1 agree
Liquid NVFP4 0.0332 92.9%
This repo 0.0178 94.8%

Speed and memory (one RTX 5090, same sitting)

Same kernels (CUTLASS SM120 block-scaled FP4 GEMMs, 48 per step), same 1.86 GiB of weights. Single stream, 512 tokens, vLLM 0.32.0 + LFM3 PR overlay, KV pool 1 GiB:

Checkpoint Decode tok/s Prefill tok/s (2.3k prompt) Weights Peak VRAM
BF16 290 33,555 3.36 GiB 5,424 MiB
Liquid NVFP4 379 54,685 1.86 GiB 3,945 MiB
This repo 402 53,368 1.86 GiB 4,001 MiB

SGLang (PR 46858): BF16 345, Liquid NVFP4 513, this repo 457 tok/s decode. The ours-vs-Liquid gap flips sign between runtimes (FlashInfer/CUTLASS autotuner tile picks); summed GPU kernel time differs by ~2%, so treat the two NVFP4 files as the same speed.

Usage

Recommended sampling (Liquid's card): temperature 0.1, top_k 50, repetition_penalty 1.1 (math/STEM: temperature 1.0, top_p 0.95, top_k 20). Thinking is on by default; tool calls use Liquid's XML format.

LFM3 is not in a vLLM or SGLang release yet (Nov 1, 2026). It works today with vLLM v0.32.0 + vllm-project/vllm PR 64959, or SGLang nightly + sgl-project/sglang PR 46858, exactly like Liquid's NVFP4:

vllm serve BennyDaBall/LFM3-1.7B-NVFP4 --trust-remote-code
python -m sglang.launch_server --model-path BennyDaBall/LFM3-1.7B-NVFP4 --reasoning-parser auto --tool-call-parser auto

License

LFM Open License v1.0 (copy in LICENSE, unchanged). Key terms, quoted from it:

"You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications" (Section 4)

"The rights granted under this License for Commercial Use are conditioned upon You or Your Legal Entity not exceeding the Threshold." (Section 5(a)), where the Threshold is "annual revenue of 10 million United States dollars ($10,000,000) or more." (Section 1)

Free for any use, commercial included, while you (and your corporate group) make under $10M a year; above that, commercial use needs a license from Liquid AI.

Credits

  • Model: Liquid AI, LFM3-1.7B. NVFP4 layer map from Liquid's own LFM3-1.7B-NVFP4.
  • Methods: GPTQ (Frantar et al. 2022), Four Over Six (Cook et al., arXiv 2512.02010), Schur Replay (arXiv 2609.36654).
  • Quantization: BennyDaBall.
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