KQuant Quantization Technique Reduces KL Divergence by Up to 3.7x for Qwen Models on MLX

·2026.11.12 19:47

Key point

Open-source KQuant packs for Qwen models on Hugging Face achieve up to 3.7x lower KL divergence than public 4-bit baselines, with 6-15% faster inference on M5 Pro for 4B, 9B, and 27B models.

Details

  • KQuant is a new quantization technique released by Nace, offering open-source MLX packs for Qwen3.5-4B, 9B, Qwen3.8-27B, Qwen3.6-35B-A3B, and Qwen3.8-Flash-Next on Hugging Face.
  • Measured against public 4-bit baselines (mlx-community or lmstudio-community), KQuant Q4 achieves lower KL divergence, with the largest improvement of 3.7x for Qwen3.8-Flash-Next (0.067 vs 0.249) and 2.6x for Qwen3.5-9B (0.030 vs 0.081).
  • The technique uses real text to determine scales and offsets for weight groups and allocates extra bits to sensitive layers, with search performed on cloud GPU clusters before release.
  • Inference speed on M5 Pro is 6-15% faster than public 4-bit packs for 4B, 9B, and 27B models when using Kapitsa 0.2.35 with the KFlash drafter; 35B is compared against Youssofal MTPLX 4-bit. No custom kernels or special loaders are required.
  • Q5 variants are also available for 9B, 27B, and 35B models, offering further precision improvements at slightly larger file sizes.

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