> ## Documentation Index
> Fetch the complete documentation index at: https://docs.summerengine.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FLUX 3 Klein

> FLUX 3 Klein on the Summer API: $0.009 per image, about 2 s, PNG, JPG, WEBP saved to your Summer library. Model id image/flux-3-klein.

The small, fast FLUX 3 for drafts under a cent.

| | |
| - | - |
| Model id | `image/flux-3-klein` |
| Price | \$0.009 per image |
| Typical time | about 2 s |
| Does | [Text to image](https://docs.summerengine.com/api/models.md#text-to-image), [Edit a picture](https://docs.summerengine.com/api/models.md#edit-a-picture) |
| Output | PNG, JPG, WEBP |
| Made by | Black Forest Labs |
| Try it | [Examples and playground on summerengine.com](https://www.summerengine.com/models/flux-3-klein) |
| Commercial use | Yes |

## Best for

* Many quick variations of an icon or item.
* Fast mood boards before choosing a style.
* Cheap reference images for 3D generation.

## Price

**\$0.009 per image**, times `numImages`. Exact list price: `0.009 USD`.

| When | Price |
| - | - |
| `removeBackground` is `true` | adds \$0.018 |

No markup: this is the provider's list price, checked 2026-10-24. A failed job costs nothing. Get the exact price of one request, free and without a key, from [`POST /v1/estimate`](https://docs.summerengine.com/api/jobs#know-the-price-first).

## Example call

Sign in once with `summer login`; over HTTP, send `Authorization: Bearer $SUMMER_TOKEN` after `export SUMMER_TOKEN=$(summer token)` ([sign-in](https://docs.summerengine.com/api/sign-in.md)). This job comes back done in the same call, with the file ready to download.

```bash CLI theme={null}
npx -y summer-engine@latest api run image/flux-3-klein \
  --input '{"prompt":"a cozy pixel-art tavern at night, warm window light","aspectRatio":"16:9"}' \
  --download .
```

```bash curl theme={null}
curl https://www.summerengine.com/v1/jobs \
  -H "Authorization: Bearer $SUMMER_TOKEN" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Prefer: wait=60" \
  -d '{"model":"image/flux-3-klein","input":{"prompt":"a cozy pixel-art tavern at night, warm window light","aspectRatio":"16:9"}}'
```

```ts TypeScript theme={null}
const res = await fetch("https://www.summerengine.com/v1/jobs", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.SUMMER_TOKEN}`,
    "Content-Type": "application/json",
    "Idempotency-Key": crypto.randomUUID(),
    Prefer: "wait=60",
  },
  body: JSON.stringify({
    "model": "image/flux-3-klein",
    "input": {
      "prompt": "a cozy pixel-art tavern at night, warm window light",
      "aspectRatio": "16:9"
    }
  }),
});
const { job } = await res.json();
console.log(job.state, job.id);
```

```python Python theme={null}
import os, uuid, requests

res = requests.post(
    "https://www.summerengine.com/v1/jobs",
    headers={
        "Authorization": f"Bearer {os.environ['SUMMER_TOKEN']}",
        "Idempotency-Key": str(uuid.uuid4()),
        "Prefer": "wait=60",
    },
    json={"model": "image/flux-3-klein", "input": {"prompt": "a cozy pixel-art tavern at night, warm window light", "aspectRatio": "16:9"}},
)
job = res.json()["job"]
print(job["state"], job["id"])
```

```js MCP theme={null}
// Summer's MCP server: npx -y summer-engine@latest setup <agent> --yes
summer_api_run({
  model: "image/flux-3-klein",
  input: {
    prompt: "a cozy pixel-art tavern at night, warm window light",
    aspectRatio: "16:9"
  },
  out: "assets",
})
```

The finished job has `state` `"done"` and `result.assets`: one entry per file, each with `assetId`, `fileUrl` (a Summer URL) and `thumbnailUrl`. Download the file into your project, or import it in Summer Engine by its asset id.

## Input

Send these fields in `input`. The full JSON Schema is `inputSchema` in [`GET /v1/models/image/flux-3-klein`](https://docs.summerengine.com/api/reference/get-models-model).

| Field | Type | About |
| - | - | - |
| `prompt` (required) | string | What to draw, or how to change the reference image. up to 4000 characters |
| `style` | `realistic`, `cartoon`, `anime`, `none` | |
| `aspectRatio` | `1:1`, `16:9`, `9:16`, `4:3`, `3:4`, `3:2`, `2:3`, `5:4`, `4:5`, `21:9` | Default 1:1. |
| `width` | integer | Smallest width wanted, in pixels; give height too. Store key art: 1920 x 1080 at 16:9. 64 to 4096 |
| `height` | integer | Smallest height wanted, in pixels; give width too. 64 to 4096 |
| `numImages` | integer | 1 to 4 Default `1`. |
| `referenceImageUrl` | string | A public image URL to edit instead of drawing from nothing. up to 2048 characters |
| `removeBackground` | boolean | Also cut out the background (transparent PNG); costs a removal per image. |
| `seed` | integer | Same seed and prompt, similar image (Nano Banana models). 0 to 9007199254740991 |
| `title` | string | up to 200 characters |

## Related models

> **[Nano Banana 2 Lite](https://docs.summerengine.com/api/models/image/nano-banana-2.md)**
>
> `image/nano-banana-2`: \$0.042 per image (default)

> **[Grok Imagine 2](https://docs.summerengine.com/api/models/image/grok-imagine-2.md)**
>
> `image/grok-imagine-2`: \$0.06 per image

> **[Muse Image](https://docs.summerengine.com/api/models/image/muse-image.md)**
>
> `image/muse-image`: \$0.01 per image

> **[Grok Imagine](https://docs.summerengine.com/api/models/image/grok-imagine.md)**
>
> `image/grok-imagine`: \$0.02 per image

## For agents

This page as Markdown: [https://docs.summerengine.com/api/models/image/flux-3-klein.md](https://docs.summerengine.com/api/models/image/flux-3-klein.md). The live record with the JSON Schema: `GET https://www.summerengine.com/v1/models/image/flux-3-klein`, public, no sign-in.


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