# FLUX.3 Klein API

> Text-zu-Bild mat natierleche 4K-Gréissten, optionaler Bounding-Box-Layoutkontroll a bis zu 4 Biller pro Ufro

Generéiert Biller aus engem detailléierten Text-`prompt`. All Säit vun `image_size` kann tëscht 256 an 4096 Pixel leien, an Dir kënnt 1 bis 4 Biller pro Ufro froen. Bis zu 32 `bounding_boxes` erlaben et, benannt Objeten op feste Positiounen am Frame ze placéieren. D'Ausgab kann png, jpeg oder webp sinn; Prompt-Erweiderung kann un- oder ausgeschalt ginn.

- Model id: `blackforestlabs/flux-3/klein/text-to-image`
- Made by: Black Forest Labs
- Category: Text to Image
- Output: image
- Price per run: from $0.008 / run of output image (cheapest run $0.008 (8 API credits))
- Run: `POST https://api.doitong.ru/v1/run/blackforestlabs/flux-3/klein/text-to-image`
- Quote: `POST https://api.doitong.ru/v1/quote/blackforestlabs/flux-3/klein/text-to-image`
- Docs page: https://doitong.com/lb/developers/models/blackforestlabs/flux-3/klein/text-to-image

## Pricing

Price: **from $0.008 / run of output image** (the lowest tier; the quote prices your exact input). Price per run: the input files are measured before the run (length, resolution, frame rate). The quote measures the same files and is exactly what the run charges.

The full example input below costs $0.009 = 9 API credits (1 run × $0.009).

Prices are the upstream price in USD, paid from the API balance in API credits (1000 API credits = 1 USD). `POST https://api.doitong.ru/v1/quote/blackforestlabs/flux-3/klein/text-to-image` with the same JSON body returns the exact price for that input; the quote is exactly what a run charges. Invalid input is never charged and failed or canceled requests are refunded automatically.

## Input parameters

Send either the canonical name or the native field name (not both). Canonical names are the same across models.

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `prompt` |  | string | yes |  |  | Instruktioune fir d'Bildgeneratioun, déi Thema, Kadreierung, Beliichtung an Hannergrond am Detail beschreiwen, entspriechend den detailléierte Captions, mat deenen de Modell trainéiert gouf. |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | Prompt-Erweiderung zu enger detailléierter Caption virun der Generatioun, aktivéiert wann true. Beim Ännere baséiert d'Caption op de Referenzbiller. |
| `seed` |  | integer \| null | no |  |  | Seed fir reproduzéierbar Biller: Dee selwechte Prompt a Seed produzéieren datselwecht Bild, wann d'Modellversioun onverännert ass. |
| `num_images` | `num_outputs` | integer | no | `1` | 1 – 4 | Ugefrote Bildzuel fir d'Generatioun. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Aktivéierung vun der Sécherheetskontroll; true aktivéiert d'Kontroll. |
| `output_format` |  | enum (string) | no | `png` | `jpeg`, `png`, `webp` | Dateiformat vum resultéierende Bild. |
| `image_size` |  | object {width, height} \| enum (string) | no | `square_hd` | `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Setzt Breet an Héicht vum Output onofhängeg bannent 256–4096 Pixel; native 4K-Generatioun gëtt ënnerstëtzt. |
| `bounding_boxes` |  | array of object {label, description, box} \| null | no |  | ≤ 32 items | Optional Këschtelayout, dat all beschriwwenen Objet op seng zougewisen Këscht limitéiert; identifizéiert Këschten iwwer Prompt-Etiketten, z. B. `A red fox <fox> sits under a red umbrella <umbrella>`. Koordinate drécken d'Këschtekante als Fraktioune vun de Bilddimensiounen aus, gemooss vum Ursprung uewen lénks (0, 0). |
| `bounding_boxes[].label` |  | string \| null | no |  | ≤ 64 characters | Kuerzt Objektetikett fir d'Këscht, wéi `fox`; de Standard ass `obj_<n>`. Maacht `<fox>` an de Prompt, fir seng Wierder mat der Këscht ze verbannen; Këschten, déi net am Prompt ernimmt ginn, ginn der Szen bäigefüügt. |
| `bounding_boxes[].description` |  | string | yes |  | ≤ 500 characters | Objekt, dat an der Këscht gerendert gëtt, inklusiv sengem Ausgesinn. |
| `bounding_boxes[].box` |  | object {x_min, y_min, x_max, y_max} | yes |  |  | Objektplazéierung am Output-Bild. |
| `bounding_boxes[].box.x_min` |  | number | yes |  | 0 – 1 | Lénks Grenz relativ zur Bildbreet, vun 0 bis 1. |
| `bounding_boxes[].box.y_min` |  | number | yes |  | 0 – 1 | Uewescht Grenz relativ zur Bildhéicht, vun 0 bis 1. |
| `bounding_boxes[].box.x_max` |  | number | yes |  | 0 – 1 | Riets Grenz relativ zur Bildbreet, vun 0 bis 1. |
| `bounding_boxes[].box.y_max` |  | number | yes |  | 0 – 1 | Ënnescht Grenz relativ zur Bildhéicht, vun 0 bis 1. |

## Example input

Required parameters only:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
}
```

A fuller example:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
}
```

## Run it

Set `DOITONG_API_KEY` to a key from https://doitong.com/developers/dashboard#keys. `?wait=20` returns the finished request in the same call when it is ready within 20 seconds; otherwise poll `GET /requests/{id}` (it also accepts `?wait=`), or pass `webhook_url`.

### curl

```bash
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.ru/v1/run/blackforestlabs/flux-3/klein/text-to-image?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  }'

# Still "queued" or "running"? Poll with the id from the response:
curl "https://api.doitong.ru/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"
```

### JavaScript

```javascript
const API = "https://api.doitong.ru/v1";
const headers = {
  "Authorization": "Bearer " + process.env.DOITONG_API_KEY,
  "Content-Type": "application/json",
};

// Run the model; wait up to 20 s for the finished result in the same call
let res = await fetch(API + "/run/blackforestlabs/flux-3/klein/text-to-image?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  }),
});
let request = await res.json();
if (!res.ok) throw new Error(request.error.code + ": " + request.error.message);

// Not finished yet: long-poll until it is
while (request.status === "queued" || request.status === "running") {
  res = await fetch(API + "/requests/" + request.id + "?wait=20", { headers });
  request = await res.json();
}
if (request.status !== "succeeded") throw new Error(JSON.stringify(request.error));
console.log(request.outputs.map((o) => o.url), request.cost.credits + " API credits ($" + request.cost.usd + ")");
```

### Python

```python
import os
import requests

API = "https://api.doitong.ru/v1"
headers = {"Authorization": "Bearer " + os.environ["DOITONG_API_KEY"]}

payload = {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/blackforestlabs/flux-3/klein/text-to-image", params={"wait": 20}, json=payload, headers=headers)
request = r.json()
if not r.ok:
    raise RuntimeError(request["error"]["code"] + ": " + request["error"]["message"])

# Not finished yet: long-poll until it is
while request["status"] in ("queued", "running"):
    request = requests.get(API + "/requests/" + request["id"], params={"wait": 20}, headers=headers).json()
if request["status"] != "succeeded":
    raise RuntimeError(request["error"])
print([o["url"] for o in request["outputs"]], request["cost"]["credits"], "API credits", "$" + request["cost"]["usd"])
```

### MCP

The MCP server at `https://api.doitong.ru/v1/mcp` exposes the tools `search_models`, `get_model`, `quote`, `run`, `get_request`, `cancel_request`, `list_requests`, `create_upload` and `get_account`. A `run` call for this model:

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "run",
    "arguments": {
      "model_id": "blackforestlabs/flux-3/klein/text-to-image",
      "input": {
        "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
      },
      "wait_seconds": 20
    }
  }
}
```

## Response

Every call returns a request object. `status` is one of `queued`, `running`, `succeeded`, `failed`, `canceled`. `outputs` lists the generated files with URLs on our storage (kept forever, or 7 days with `?storage=temporary`; `storage` says which); `output` is the model's own result object with the same URLs.

```json
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "blackforestlabs/flux-3/klein/text-to-image",
  "status": "succeeded",
  "created_at": "2026-10-20T12:00:00Z",
  "started_at": "2026-10-20T12:00:02Z",
  "completed_at": "2026-10-20T12:00:09Z",
  "queue_position": null,
  "cost": {
    "credits": 9,
    "usd": "0.009",
    "charged": 9,
    "refunded": 0
  },
  "input": {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  },
  "output": {
    "images": [
      {
        "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
        "content_type": "image/jpeg",
        "file_name": "0-output.jpeg",
        "file_size": 1843200,
        "width": 1024,
        "height": 768
      }
    ],
    "timings": {},
    "seed": 42,
    "has_nsfw_concepts": [
      false
    ],
    "prompt": "string"
  },
  "outputs": [
    {
      "type": "image",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_size": 1843200,
      "width": 1024,
      "height": 768,
      "stored": true
    }
  ],
  "error": null,
  "metrics": {
    "inference_seconds": 6.8
  },
  "urls": {
    "self": "https://api.doitong.ru/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.ru/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
```

### Output fields (`output`)

| Field | Type | Description |
|---|---|---|
| `images` | array of object {url, content_type, file_name, file_size, width, height} | Biller, déi vum Modell erstallt goufen. |
| `timings` | object | Zäitinformatioun fir de Generatiounsprozess. |
| `seed` | integer | Generatiounsseed fir dat éischt Bild. |
| `has_nsfw_concepts` | array of boolean | Gëtt un, ob NSFW-Konzepter an de generéierte Biller optrieden. |
| `prompt` | string | Prompt, deen während der Bild-Generatioun benotzt gëtt. |

## Related models

- [FLUX.3 Klein Image Editing](https://doitong.com/developers/models/blackforestlabs/flux-3/klein/edit-image.md) (`blackforestlabs/flux-3/klein/edit-image`): from $0.008 / run of output image
- [FLUX.1 \[dev\]](https://doitong.com/developers/models/flux/dev.md) (`flux/dev`): $0.025 / megapixel
- [FLUX.1 \[schnell\]](https://doitong.com/developers/models/flux/schnell.md) (`flux/schnell`): $0.003 / megapixel
- [FLUX.2 \[dev\]](https://doitong.com/developers/models/flux-2.md) (`flux-2`): $0.012 / megapixel
- [FLUX.2 \[pro\]](https://doitong.com/developers/models/flux-2-pro.md) (`flux-2-pro`): $0.015 / megapixel of output image
- [GPT Image 2.5 Text to Image](https://doitong.com/developers/models/openai/gpt-image-2.5/flare/text-to-image.md) (`openai/gpt-image-2.5/flare/text-to-image`): from $0.008 / image
- [Ideogram V4.5](https://doitong.com/developers/models/ideogram/v4.5.md) (`ideogram/v4.5`): from $0.03 / image
- [Nano Banana 2](https://doitong.com/developers/models/nano-banana-2.md) (`nano-banana-2`): from $0.06 / image

## Links

- HTML page: https://doitong.com/developers/models/blackforestlabs/flux-3/klein/text-to-image
- All models and guides for AI agents: https://doitong.com/developers/llms.txt
- OpenAPI 3.1 with this model's typed request body: https://doitong.com/developers/openapi.json?model=blackforestlabs/flux-3/klein/text-to-image
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.ru/v1/models/blackforestlabs/flux-3/klein/text-to-image