df11pack

AI-built, human-directed: Claude Code (Anthropic) did most of the coding, debugging and test runs; the author chose what to build and measure, and decides what is published.

A fast, independent compressor for DFloat11: lossless compression of BF16 model weights to about 70% of their size, decoded on the GPU by the official CUDA kernel.

df11pack writes the same files the official compressor writes — byte for byte — so every existing DFloat11 loader works unchanged: DFloat11Model for LLMs and diffusers, and ComfyUI-DFloat11-Extended for ComfyUI. It is just much faster and lighter, and needs no GPU and no Python.

Measured

Qwen3-8B, compressed on the same 8-vCPU machine:

	official compressor	df11pack
time	37 min	40 s
peak RAM	27.3 GiB	6.6 GiB
output	39 .safetensors files, 11.16 GB	the same 39 files, byte-identical

All 39 files are also byte-identical to the published DFloat11/Qwen3-8B-DF11 release (SHA-256 compared file by file). On an old dual-core laptop with no GPU, Qwen3-0.6B (layers only) takes 11 s against the official 13 min. Details and every other measurement: docs/FINDINGS.md, raw run data in gpu_session/qwen3_8b/results/.

Install

Download the archive for your platform from Releases, unpack, and run df11pack. One static binary; nothing else to install. Linux (x86_64, aarch64), Windows (x86_64) and macOS (Apple Silicon).

Or build from source (Rust 1.85+): cargo build --release -p df11pack.

Use

df11pack architectures                      # what it can compress

ComfyUI — a single .safetensors for ComfyUI-DFloat11-Extended:

df11pack compress flux1-schnell.safetensors --arch flux-schnell-comfyui -o out/
# -> out/model.safetensors

diffusers — a directory DFloat11Model.from_pretrained loads:

df11pack compress FLUX.1-schnell/transformer/ --arch flux-dev-diffusers -o out/

LLMs (transformers):

df11pack compress Qwen3-8B/ --arch qwen3-8b -o Qwen3-8B-DF11/

Useful options:

• --safe decodes every unit and checks it against the source before writing it;
• --ram 4G sizes the worker count to fit a memory budget (by default, what is free on Linux; elsewhere one worker per core);
• --io sequential for spinning hard drives (auto-detected on Linux).

Check any output, including ones you did not make:

df11pack verify out/                                        # structure, no source needed
df11pack verify out/ --source model/ --arch qwen3-8b        # + 1000 sampled chunks decoded
df11pack verify out/ --source model/ --arch qwen3-8b --level full

verify exits 0 on pass, 1 when a check fails, 2 when it could not check.

Models

35 definitions ship built in (df11pack architectures):

• every official DFloat11 release with a dfloat11_config — 40 of the 45 in the DFloat11 Hugging Face organisation: Qwen3, Qwen2.5, Llama, Mistral, Phi-4, Gemma-3, DeepSeek-R1 distills, FLUX.1 (dev/schnell/Kontext/Krea/Fill/Depth/Canny), Chroma, HiDream, Qwen-Image, Wan 2.1/2.2, SD3.5, OmniGen2, BAGEL;
• every model in ComfyUI-DFloat11-Extended (ComfyUI files): Flux, Flux.2, Chroma, Chroma-Radiance, Qwen-Image 2.1, Z-Image, Lumina 2, Cosmos-Predict2, Anima, ERNIE-Image, LongCat, Ovis, Krea-2, Lens, SDXL, ACE-Step 1.5.

A new model is a small TOML file; pass its path to --arch, or put it in a folder named by DF11PACK_ARCH_DIR (the file name without .toml is then the name --arch takes). Format and how to add one: docs/DEFINITIONS.md.

What is checked, and what is not

• Byte-identity with the official compressor is tested per architecture, on small models run through the official tool, and on real Qwen3 models (0.6B, 8B).
• 28 of the 35 definitions were checked against the tensor names of real checkpoints and real published DF11 files; 23 of 28 match exactly, and the other 5 have sources in F32/F16, which df11pack refuses (convert to BF16 first). The Llama definition was checked through Mistral-Nemo, which shares it. Not checked: Gemma-3, SD3.5 and FLUX.1-dev/Kontext diffusers (gated repositories), and the ComfyUI flux, flux2-alt and zimage-pixel-space definitions.
• Two of mingyi456's published ComfyUI releases were rebuilt from their sources and compared (2026-09-28, phase0/check_comfyui_release.sh): Lumina-Image-2.0 (402 tensors) and Chroma1-HD (777 tensors) are byte-identical, file SHA-256 included (phase0/results/comfyui/). The other ComfyUI definitions were checked by tensor names only, except the three not checked above.
• Not yet done: loading df11pack's output in ComfyUI on a GPU for the image models. For Lumina-Image-2.0 and Chroma1-HD the output is byte-identical to releases that loader already reads, so it is expected to work (not tested); reports welcome.

Beyond the official format, all opt-in and clearly marked:

• --luts=correct — zero-fills LUT entries the official encoder leaves as leftovers; unreachable by construction, and measured so with the official kernel on the one real leak (docs/COMPATIBILITY.md).
• --hashes — per-tensor SHA-256 in the header, so verify catches corruption without the source; tensor bytes unchanged.
• --index idx8 — an experimental 8-bit block index, 0.66% smaller. Not DFloat11: no current loader reads it (docs/INDEX_SCHEMES.md).

Documents

• docs/DEFINITIONS.md: the model definition format.
• docs/COMPATIBILITY.md: what the output promises.
• docs/FINDINGS.md: every measurement, and what each changed.
• docs/DESIGN.md, docs/PLAN.md: the original design and build plan.
• CHANGELOG.md.

How this was made

Written with Claude Code (Anthropic), under the author's direction. Claude Code wrote most of the code and documentation and ran the tests and measurements; the author chose what to build and measure, and decided what to publish. Every commit carries a Co-Authored-By trailer, so who did what can be checked in the git history.

The rules the work follows (evidence, wording, logs, tests, publishing) are in NORMS.md, shared by all the repos of this project.

Contributing

Testing a model on a GPU and reporting how it went helps most right now. See CONTRIBUTING.md; questions go to Discussions, vulnerabilities to SECURITY.md. Everyone taking part follows the Code of Conduct.

Reporting a problem

Found a problem, or a number that does not match? Please tell us: REPORTING.md says what helps.

Licence

MIT — see LICENSE. Free to use, modify and redistribute; keep the copyright notice.

df11pack reimplements the DFloat11 file format and its codebook construction from the official implementation (Apache-2.0, https://github.com/LeanModels/DFloat11, by the DFloat11 authors) and reads model definitions derived from ComfyUI-DFloat11-Extended (by mingyi456; its repository has no licence file). It contains no code from either and does not redistribute decode.ptx. All credit for the format goes to them.