---
title: flux-3-image-klein-bf16
canonical_url: "https://www.modelscope.cn/models/mlx-community/flux-3-image-klein-bf16"
md_url: "https://www.modelscope.cn/models/mlx-community/flux-3-image-klein-bf16.md"
repository: mlx-community/flux-3-image-klein-bf16
last_updated: 2026-10-18
license: other
pipeline_tag: image-to-image
tasks:
  - image-to-image
base_model:
  - black-forest-labs/flux-3-image-klein
base_model_relation: finetune
parameters: 5.5B
tensor_type:
  - BF16
  - F32
  - I64
library_name:
  - mlx
  - lora
  - safetensors
  - diffusers
  - pytorch
frameworks:
  - pytorch
language:
  - en
downloads: 59
stars: 0
tags:
  - mlx
  - safetensors
  - apple-silicon
  - text-to-image
  - image-editing
  - flux
  - flux-3
---

# flux-3-image-klein-bf16

> flux-3-image-klein-bf16 - mlx-community 在 ModelScope 开源的模型。mlx-community/flux-3-image-klein-bf16

mlx-community/flux-3-image-klein-bf16 是 ModelScope 魔搭社区上的 5.5B 参数image-to-image模型，采用 other 许可，基于 black-forest-labs/flux-3-image-klein 构建。

- **Repository**: mlx-community/flux-3-image-klein-bf16
- **License**: other
- **Tasks**: image-to-image
- **Parameters**: 5.5B
- **Base model**: black-forest-labs/flux-3-image-klein
- **Tags**: mlx, safetensors, apple-silicon, text-to-image, image-editing, flux, flux-3
- **Downloads**: 59
- **Stars**: 0
- **Last updated**: 2026-10-18

Source: https://www.modelscope.cn/models/mlx-community/flux-3-image-klein-bf16

---

# mlx-community/flux-3-image-klein-bf16

> This FLUX Model is licensed by Black Forest Labs Inc. under the FLUX Kommunity License. Copyright Black Forest Labs Inc.
> IN NO EVENT SHALL BLACK FOREST LABS INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
> CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH USE OF THIS MODEL.

This repo is an Apple Silicon copy of **[black-forest-labs/flux-3-image-klein](https://huggingface.co/black-forest-labs/flux-3-image-klein)**
for the Swift/MLX port [flux3-klein-swift](https://github.com/xocialize/flux3-klein-swift).
- **The files are unmodified.** Every file here is byte-identical to upstream revision `33733762` (sha256 checked).
  MLX loads these bf16 safetensors directly, and the int8 / int4 tiers are made when the model loads.
- **It is an independent port.** It is not an official Black Forest Labs product, and BFL has not endorsed or
  validated it.

## Licence: read it before you use this model

The DiT and autoencoder are under the **[FLUX Kommunity License v1.0](LICENSE.md)**:
- **Non-commercial use** is permitted.
- **Commercial use of outputs** is permitted only for a "Qualifying User": under US$5M gross annualized revenue,
  affiliates included. You must also filter content (or review outputs) and disclose AI generation where the law
  requires it (§2(a), §2(e)).
- **No training on outputs:** you may not use the model, its derivatives or its outputs to improve any other AI model
  that performs a similar function (§4(b)).

Read the full licence for the other restrictions and for termination. For any other commercial use, see
[bfl.ai/licensing](https://bfl.ai/licensing). The text encoder (`text_encoder/`, byte-identical to
[Qwen/Qwen3-VL-4B-Instruct](https://huggingface.co/Qwen/Qwen3-VL-4B-Instruct)) is Apache-2.0 (`text_encoder/LICENSE`).

## Model

FLUX 3 Image Klein does text-to-image, single-reference editing and multi-reference composition (up to 10 references)
in one model. Bounding-box layout goes in the prompt, and the model renders text.

- **DiT (5.55B):** each mode (image, references, text) has its own 5-block stack; then come 28 shared single-stream
  blocks with per-token modulation. It is a **flow-map** distill: 16 steps, no CFG.
- **Conditioner:** 8 hidden-state taps (layers 4…32) of Qwen3-VL-4B-Instruct, text only, giving 20480-d features.
- **Autoencoder:** the FLUX.2 VAE, the same weights as FLUX.2 [klein]. `vae/` is the diffusers form the port loads;
  `ae.safetensors` is BFL's native form.

| File | What |
|---|---|
| `model.safetensors`, `config.json`, `manifest.json` | the distilled DiT, bf16, in BFL's native key names (359 tensors) |
| `text_encoder/` | Qwen3-VL-4B-Instruct, bf16 |
| `vae/`, `ae.safetensors` | the autoencoder, fp32 |
| `LICENSE.md`, `NOTICE.md` | the FLUX Kommunity License and BFL's attribution notice |

**Prompting.** The model expects a **full scene caption** (medium, scene, lighting, each subject's colours, materials and
position). Run a prompt upsampler first: BFL's Apache-2.0
[flux-3-image-klein-pup](https://huggingface.co/black-forest-labs/flux-3-image-klein-pup), or any LLM given its
`system_prompts.json`. Layout boxes go after the caption as a JSON list on a 0–1000 grid; see the upstream card.

## Sampling

| Setting | Value |
|---|---|
| Sampler | flow-map Euler; t′ = α·t / (1 + (α − 1)·t) over linspace(1, 0, 17) |
| Steps | 16 |
| α | **6.93** (`config.json`). BFL's reference CLI defaults to 16.0, which does not reproduce BFL's example renders (35.8 vs 23.1 dB on the knitted example) |
| Guidance | none |

## Parity (Swift/MLX port vs BFL's reference code, fp32)

| Component | Result |
|---|---|
| DiT, one forward, all stages (t2i, 1 ref, 3 refs) | cos ≥ 0.9999998, relMax ≤ 2.1e-5 |
| DiT, 16-step 512² trajectory | relMax ≤ 1.7e-4 at every step |
| Conditioner (8 taps, real and padded rows) | cos ≥ 0.99998 |
| VAE encode / decode | cos 0.999999 / 0.9999999 |
| Reference prep (fit, pad, crop) | byte-identical |
| bf16 end to end vs BFL's own example PNGs (same noise) | 35.9 / 39.8 / 52.7 / 30.9 dB; BFL's code on MPS scores 35.8 / 42.5 / 56.2 |

## Quant tiers, text fidelity and memory (M5 Max 128 GB)

The DiT tiers are made **when the model loads**: affine, group 64, block by block from the bf16 file. Embeddings,
timestep MLPs, modulations and the final layer stay bf16.
- **int4** keeps every block's attention projections at 8 bits. Plain int4 drifted too far from bf16.
- The text encoder loads **text-only** (the vision tower is never read). It can also be int8.

**Text fidelity** (an OCR gate: 20 long-text EN/ZH prompts × 2 seeds per lane, Apple Vision OCR, Δ against bf16 with
a 95 % bootstrap CI; tolerance pre-registered at ΔCER ≤ +1 pp):

| DiT + encoder | CER | ΔCER vs bf16 | exact strings | Verdict |
|---|---|---|---|---|
| bf16 + bf16 | 3.00 % (EN 0.19 %) | — | 68.7 % (EN 95.8 %) | baseline |
| int8 + bf16 | 2.61 % | −0.39 pp [−0.85, −0.05] | 72.4 % | within tolerance |
| int4 (8-bit attn) + bf16 | 3.10 % | +0.10 pp [−0.69, +0.91] | 71.6 % | within tolerance |
| bf16 + int8 | 2.95 % | −0.05 pp [−0.32, +0.21] | 69.4 % | within tolerance |
| int8 + int8 | 3.05 % | +0.05 pp [−0.33, +0.46] | 68.7 % | within tolerance |

English text is excellent; Chinese is weak in every tier (12 % CER). int4 keeps text, but at a given seed it is a
visibly different render from bf16 (21.9–35.5 dB on BFL's examples, against 31–50 dB for int8).

**Memory** (MLX with a 2 GB buffer-pool cap, phys_footprint peak of the whole process):

| DiT + encoder | Resident (MLX) | Peak, 1024² T2I or edit | Peak, encoder dropped after encoding |
|---|---|---|---|
| bf16 + bf16 | 19.5 GB | 31.8 GB (4 refs: 32.2 GB) | 24.1 GB |
| int8 + bf16 | 14.5 GB | 26.9 GB | — |
| int4 (8-bit attn) + bf16 | 12.7 GB | 25.1 GB | — |
| bf16 + int8 | 16.1 GB | 28.4 GB | — |
| int8 + int8 | 11.1 GB | 23.5 GB | 18.8 GB |

- About 11 GB of each 1024² peak is the fp32 VAE decode.
- A single reference at the 4 MP cap (2048² canvas and output) peaks at 51–58 GB. It needs a 64 GB Mac.

**Speed** (16 steps, the same in every tier):

| Request | Time |
|---|---|
| T2I | ~1.0–1.2 s per step |
| One reference | ~2.3 s per step |
| Four references | ~10 s per step |
| 4 MP single reference at 2048² | ~20 s per step |

## Use (Swift)

```swift
import Flux3Klein

let pipe = try await Flux3KleinPipeline.load(snapshot: snapshotURL, quant: .bf16)   // or .int8 / .int4
let result = try pipe.generate(.init(prompt: caption, references: [try Flux3RGBImage.read(url: photoURL)]))
try result.image.write(to: outURL)
```

Code: https://github.com/xocialize/flux3-klein-swift (Swift/MLX port, MIT; the weights stay under the FLUX Kommunity
License).