# FLUX.2 Klein

ID: black-forest-labs/flux.2-klein-4b
Type: image generation
Vendor: Black Forest Labs
Released: 2026-01-15
Commercial use: allowed
Description: FLUX.2 [klein] 4B is a step-distilled open-weight model for sub-second text-to-image and multi-reference editing, designed for consumer GPUs under Apache 2.0.

## Modes and inputs
- Text → Image (`txt->img`)
  - Prompt only, no input images
- Image → Image (`img->img`)
  - any image: up to 4

## Output
- Aspect ratios: 3:2, 2:3, 16:9, 9:16, 1:1. Other ratios snap to the closest one. Without `size` (or with `"auto"`), Mynth picks a ratio for the prompt.
- 4K: no
- Negative prompt: not supported (dropped, no error)

## Pricing (USD)
- Per image: $0.0010
- Per input image: Free, charged once for each image it goes into
- Only successful results are charged.

## Usage
Set the request's `model` field to `black-forest-labs/flux.2-klein-4b`. Always pass it explicitly.

TypeScript SDK, Text → Image:

```ts
import Mynth from "@mynthio/sdk";

const mynth = new Mynth();

const task = await mynth.image.generate({
  model: "black-forest-labs/flux.2-klein-4b",
  prompt: "A lighthouse at dusk, 35mm film",
  size: "16:9",
});

console.log(task.urls[0]);
```

REST (cURL), Text → Image:

```bash
curl https://api.mynth.io/image/generate \
  -H "Authorization: Bearer $MYNTH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "black-forest-labs/flux.2-klein-4b",
    "prompt": "A lighthouse at dusk, 35mm film",
    "size": "16:9"
  }'
```

CLI, Text → Image:

```bash
npx @mynthio/cli image generate \
  -m black-forest-labs/flux.2-klein-4b \
  -p "A lighthouse at dusk, 35mm film" \
  -s 16:9
```

TypeScript SDK, Image → Image:

```ts
import Mynth from "@mynthio/sdk";

const mynth = new Mynth();

const task = await mynth.image.generate({
  model: "black-forest-labs/flux.2-klein-4b",
  prompt: "The same lighthouse, now in heavy fog",
  inputs: ["https://cdn.example.com/lighthouse.png"],
});

console.log(task.urls[0]);
```

REST (cURL), Image → Image:

```bash
curl https://api.mynth.io/image/generate \
  -H "Authorization: Bearer $MYNTH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "black-forest-labs/flux.2-klein-4b",
    "prompt": "The same lighthouse, now in heavy fog",
    "inputs": ["https://cdn.example.com/lighthouse.png"]
  }'
```

CLI, Image → Image:

```bash
npx @mynthio/cli image generate \
  -m black-forest-labs/flux.2-klein-4b \
  -p "The same lighthouse, now in heavy fog" \
  -i https://cdn.example.com/lighthouse.png
```

## Links
- Model page: https://mynth.io/models/black-forest-labs%2Fflux.2-klein-4b
- Playground: https://mynth.io/playground?_m=black-forest-labs%2Fflux.2-klein-4b
- Vendor page: https://bfl.ai/models/flux-2-klein
- License: https://www.apache.org/licenses/LICENSE-2.0
- API docs (image generation request): https://mynth.io/docs/api-reference/endpoints/image/generate.md
- Quickstart: https://mynth.io/docs/getting-started.md
- SDK (JS/TS): https://mynth.io/docs/sdks/typescript.md
- This page as JSON: https://mynth.io/models/black-forest-labs%2Fflux.2-klein-4b.json

## More from Black Forest Labs
- FLUX.1 Schnell [black-forest-labs/flux-1-schnell]: https://mynth.io/models/black-forest-labs%2Fflux-1-schnell.md
- FLUX.3 [black-forest-labs/flux-3]: https://mynth.io/models/black-forest-labs%2Fflux-3.md
- FLUX.3 Klein [black-forest-labs/flux-3-klein]: https://mynth.io/models/black-forest-labs%2Fflux-3-klein.md
- FLUX.1 Dev [black-forest-labs/flux.1-dev]: https://mynth.io/models/black-forest-labs%2Fflux.1-dev.md
- FLUX.2 Dev [black-forest-labs/flux.2-dev]: https://mynth.io/models/black-forest-labs%2Fflux.2-dev.md
- FLUX.2 Flex [black-forest-labs/flux.2-flex]: https://mynth.io/models/black-forest-labs%2Fflux.2-flex.md
- FLUX.2 Max [black-forest-labs/flux.2-max]: https://mynth.io/models/black-forest-labs%2Fflux.2-max.md
- FLUX.2 Pro [black-forest-labs/flux.2-pro]: https://mynth.io/models/black-forest-labs%2Fflux.2-pro.md

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