FLUX.2 Klein 4B vs 9B: What the Official Cards Say

By Dominic Marrocco, 42 UK Research. Technical claims below are bounded to the linked primary sources.

United States model-card edition · evidence review: August 5, 2026

What a model card can—and cannot—prove

The retained URL contains an obsolete “2gb” premise. The page itself now follows the official records: Black Forest Labs states that the 4B base model can run with as little as 13 GB of VRAM in its documented setup. No cited official source establishes the old 2 GB claim, and 42 UK has not published a reproducible run that does so.

4B card: the recorded facts

• The repository name identifies a four-billion-parameter base model.
• The card describes image generation and editing.
• The weights are published under Apache 2.0.
• The publisher states “as little as 13 GB of VRAM” for the documented configuration.

9B card: the recorded facts

• The card identifies a nine-billion-parameter flow model with a Qwen3 eight-billion-parameter text embedder.
• It describes the release as distilled for four-step generation.
• It describes image generation and editing.
• The cited release uses the FLUX non-commercial licence.
• The publisher says the model fits in about 29 GB of VRAM.

Those facts do not establish that one variant is better, faster or more memory-efficient in a particular ComfyUI workflow. Such conclusions require controlled runs and raw results.

ComfyUI evidence chain

Use ComfyUI’s official repository for maintained installation routes and the official requirements page for current compatibility information. If memory allocation fails, the official troubleshooting guide lists supported mitigations. Do not turn a troubleshooting flag into a hardware guarantee.

From publisher claim to independent result

A 42 UK result must name the exact model revision, workflow, precision, dimensions, batch size, software versions, launch flags and measurement method. The benchmark hub defines that record, the installation matrix captures the environment, and the workflow library publishes the tested asset.