FLUX.2 Klein 9B SDNQ Float4 Dynamic SVD r128

Quality-oriented SDNQ quantization of black-forest-labs/FLUX.2-klein-9B, using dynamic float4_e4m0fnu quantization with SVD rank 128.

This checkpoint is intended as the quality-focused counterpart to the smaller and faster WaveCut/FLUX.2-klein-9B-SDNQ-uint4-static. It keeps the same 4-step FLUX.2 Klein workflow while spending more VRAM and a small amount of latency on dynamic quantization plus SVD reconstruction.

The image above is a compressed WebP version of a 1:1 comparison canvas. It contains the original FLUX.2 Klein 9B, the previous SDNQ baseline, the deployment-oriented uint4-static checkpoint, and this quality-oriented dynamic SVD candidate across text-heavy prompts including an additional Russian-only chalkboard prompt.

Why This Variant

We compared broad SDNQ 4-bit recipes across speed, VRAM, and visual quality. This dynamic SVD recipe was kept as the quality-oriented alternative because it uses a more conservative quantization recipe than plain static UINT4:

Dynamic quantization with threshold 0.01.
float4_e4m0fnu weights.
SVD enabled with rank 128 and 32 SVD steps.
Strong visual prompt-following behavior in the text/detail stress grid, with only a modest latency increase versus the fastest final candidate.

If the main priority is minimum memory and speed, use WaveCut/FLUX.2-klein-9B-SDNQ-uint4-static instead.

Benchmark Setup

Measurements below use a single NVIDIA A40 test host and a consistent Flux2KleinPipeline inference harness.

GPU: NVIDIA A40 46 GB
Resolution: 1024x1024
Steps: 4
Guidance scale: 0.0
Torch dtype: bfloat16
Quantized matmul: enabled for SDNQ inference comparisons
Batch/concurrency: single process

These are deployment-oriented measurements for one hardware/software setup.

Candidate Benchmark

Single-process inference metrics for the final candidate set:

Variant	Warm avg	GPU peak	CUDA allocated
`uint4-static`	3.826 s	14.8 GB	14.1 GB
`int4-dynamic-th0p1-svd-r16-s32-g128`	4.020 s	14.3 GB	13.5 GB
`uint4-static-svd-r32-s32`	4.070 s	14.7 GB	13.9 GB
`float4_e4m0fnu-dynamic-th0p1-svd-r16-s32`	4.116 s	16.0 GB	15.3 GB
This `float4_e4m0fnu-dynamic-th0p01-svd-r128-s32` checkpoint	4.185 s	17.2 GB	16.5 GB

Stress Comparison

This stress set contains 9 prompts with signs, chalkboards, posters, labels, timetables, small props, and a Russian-only chalkboard prompt. Each row was run twice; the table reports the warm run average.

Model	Warm avg	GPU peak	CUDA allocated	Prompt count
Original `FLUX.2-klein-9B` BF16 pipeline	4.244 s	36.3 GB	35.6 GB	9
Previous SDNQ baseline	4.079 s	15.2 GB	14.5 GB	9
`uint4-static` checkpoint	3.866 s	14.8 GB	14.1 GB	9
This dynamic SVD r128 checkpoint	4.182 s	17.2 GB	16.5 GB	9

The model-card image is a WebP copy optimized from the full-resolution comparison canvas:

WebP quality	Size	RGB PSNR	Luma SSIM-like score
85	5.72 MB	46.93 dB	0.999977

The source JPEG canvas was about 13 MB; this WebP version is smaller while remaining visually close to the original artifact.

Model Size

Approximate full-pipeline folder sizes in the measured setup:

Checkpoint	Folder size
Original `black-forest-labs/FLUX.2-klein-9B`	52.9 GB
Previous SDNQ baseline	12.6 GB
`uint4-static` checkpoint	12.2 GB
This dynamic SVD r128 checkpoint	14.7 GB

Usage

Install current Diffusers and SDNQ:

pip install git+https://github.com/huggingface/diffusers.git
pip install sdnq

Run with Flux2KleinPipeline:

import torch
from diffusers import Flux2KleinPipeline
from sdnq import SDNQConfig  # registers SDNQ support in diffusers/transformers
from sdnq.common import use_torch_compile as triton_is_available
from sdnq.loader import apply_sdnq_options_to_model

repo_id = "WaveCut/FLUX.2-klein-9B-SDNQ-float4_e4m0fnu-dynamic-th0p01-svd-r128-s32"
device = "cuda"

pipe = Flux2KleinPipeline.from_pretrained(
    repo_id,
    torch_dtype=torch.bfloat16,
)

if triton_is_available and torch.cuda.is_available():
    pipe.transformer = apply_sdnq_options_to_model(
        pipe.transformer,
        use_quantized_matmul=True,
    )
    pipe.text_encoder = apply_sdnq_options_to_model(
        pipe.text_encoder,
        use_quantized_matmul=True,
    )

pipe.to(device)

prompt = "A clean editorial poster with large readable text: OPEN SOURCE IMAGE MODEL"
image = pipe(
    prompt=prompt,
    height=1024,
    width=1024,
    num_inference_steps=4,
    guidance_scale=0.0,
    generator=torch.Generator(device=device).manual_seed(0),
).images[0]

image.save("flux2-klein-sdnq-quality-svd.png")

The same pipeline also supports image editing:

from diffusers.utils import load_image

input_image = load_image("input.png")
image = pipe(
    image=input_image,
    prompt="Turn the handwritten sign into a clean printed sign while preserving the scene",
    height=1024,
    width=1024,
    num_inference_steps=4,
    guidance_scale=0.0,
    generator=torch.Generator(device=device).manual_seed(1),
).images[0]
image.save("flux2-klein-sdnq-quality-svd-edit.png")

If your GPU has less VRAM, replace pipe.to(device) with pipe.enable_model_cpu_offload().

Quantization Recipe

This checkpoint was produced with SDNQ post-load quantization over the transformer and text_encoder components of FLUX.2 Klein 9B.

Recipe:

variant = {
    "weights_dtype": "float4_e4m0fnu",
    "use_dynamic_quantization": True,
    "dynamic_loss_threshold": 0.01,
    "use_svd": True,
    "svd_rank": 128,
    "svd_steps": 32,
    "group_size": 0,
    "dequantize_fp32": False,
    "quantized_matmul_dtype": None,
    "use_quantized_matmul": False,
    "use_stochastic_rounding": False,
}

The measured quantization run for this recipe took about 83.4 s, with approximately 13.0 GB peak GPU memory and 38.8 GB peak CPU RSS in the test environment.

Minimal quantization sketch:

import torch
from diffusers import Flux2KleinPipeline
from sdnq import sdnq_post_load_quant
from sdnq.loader import save_sdnq_model

base_model = "black-forest-labs/FLUX.2-klein-9B"
pipe = Flux2KleinPipeline.from_pretrained(
    base_model,
    torch_dtype=torch.bfloat16,
)

common_kwargs = dict(
    weights_dtype="float4_e4m0fnu",
    torch_dtype=torch.bfloat16,
    group_size=0,
    svd_rank=128,
    svd_steps=32,
    dynamic_loss_threshold=0.01,
    use_svd=True,
    quant_conv=False,
    quant_embedding=False,
    use_quantized_matmul=False,
    use_quantized_matmul_conv=False,
    use_dynamic_quantization=True,
    use_stochastic_rounding=False,
    dequantize_fp32=False,
    non_blocking=True,
    add_skip_keys=True,
    quantization_device="cuda",
    return_device="cuda",
)

pipe.transformer = sdnq_post_load_quant(pipe.transformer, **common_kwargs)
pipe.text_encoder = sdnq_post_load_quant(pipe.text_encoder, **common_kwargs)

save_sdnq_model(
    pipe,
    "FLUX.2-klein-9B-SDNQ-float4_e4m0fnu-dynamic-th0p01-svd-r128-s32",
    max_shard_size="5GB",
    is_pipeline=True,
)

Limitations

This is a quantized derivative of FLUX.2 Klein 9B; it inherits the base model's limitations and acceptable-use requirements.
Text rendering can still be inaccurate, especially for long strings or small background text.
The quality comparison here is visual prompt-following evaluation, not a large-scale human preference or FID benchmark.
Benchmarks were run on an A40 test host and should be validated again for your exact serving stack.

License

This model is a quantized derivative of black-forest-labs/FLUX.2-klein-9B and follows the FLUX Non-Commercial License. Please review LICENSE.md and the Black Forest Labs acceptable-use policy before use.

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