FLUX.2-klein-4B-GGUF

FLUX.2-klein-4B GGUF

Self-quantized GGUF builds of black-forest-labs/FLUX.2-klein-4B for low-VRAM / edge inference. Runs on an 8GB GPU, or CPU-only.

These weights were produced with stable-diffusion.cpp (--mode convert) and are intended for use with stable-diffusion.cpp / GGUF-aware runtimes. FLUX.2 is by Black Forest Labs; klein 4B is Apache-2.0.

Files & precision

Only the heavy MLP / attention / linear weights are quantized (via --tensor-type-rules); norms and embeddings are kept at higher precision, which preserves quality at low bit-depth.

Quantization rule used:

^.*(_mlp\.(0|2)|_attn\.(proj|qkv)|\.linear(1|2))\.weight=<qtype>

Which to pick: Q4_K is the recommended balance for 8GB. Q5_K for best fidelity if you have headroom. Q2_K for the tightest RAM / smallest storage (softer detail).

Required companion files (not included here)

• VAE: flux2-vae.safetensors — e.g. Comfy-Org/flux2-dev (split_files/vae/flux2-vae.safetensors)
• Text encoder: Qwen3-4B — e.g. unsloth/Qwen3-4B-GGUF (Qwen3-4B-Q4_K_M.gguf)

Usage (stable-diffusion.cpp)

sd-cli \
  --diffusion-model flux-2-klein-4b-Q4_K.gguf \
  --vae flux2-vae.safetensors \
  --llm Qwen3-4B-Q4_K_M.gguf \
  -p "a red fox in an autumn forest, golden hour" \
  --cfg-scale 1.0 --steps 4 --sampling-method euler \
  -W 768 -H 768 --offload-to-cpu --diffusion-fa --vae-tiling -o out.png

klein is step-distilled: use 4 steps and CFG 1.0 (euler). A minimal pure C++ front-end is available as sd-flux2.cpp.

Reference latency (RTX A2000 8GB, 768×768, 4 steps, end-to-end)

Acknowledgements

• Base model: FLUX.2 [klein] 4B — Black Forest Labs (Apache-2.0)
• Quantization + inference engine: stable-diffusion.cpp (leejet), built on ggml