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FLUX.2 [klein] 4B

Integrate

Model id flux-2/klein/4b
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/flux-2/klein/4b?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.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"

This request: $0.005 5 API credits Run it on this page

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Black Forest Labs Text to Image

Compact 4B text-to-image model that runs in just 4 to 8 steps, producing up to 4 images per request

Black Forest Labs · Image

Your first result goes here

Build a request below and run it with your API key. Outputs are copied to our storage, kept forever or 7 days for free.

Build a request

Controls are generated from the model schema. The code and the price update as you change them.

•required

Prompt that guides image generation.

image_size default landscape_4_3

Dimensions for the image being generated.

num_images default 1

Image count requested for generation.

Advanced output_format · num_inference_steps · seed · enable_safety_checker
output_format default png

File format for the resulting image.

default 4

Count of inference steps to run.

Generation seed override; omitting it lets generation choose a seed at random.

POST /run/flux-2/klein/4b?wait=20 quote → $0.005
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/flux-2/klein/4b?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.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"

Run this request

Your key stays in this browser: it is sent only to the Doitong API and saved (localStorage) only if you tick Remember. Get an API key

About FLUX.2 [klein] 4B

Generates images from a text `prompt` with a small step budget: `num_inference_steps` accepts 4 to 8, default 4. Pick an `image_size` preset from square to portrait_16_9 and landscape_16_9 (default landscape_4_3), and ask for 1 to 4 images in png, jpeg or webp. A `seed` can be fixed for repeatable output. This is the generation-only version, without image inputs.

Parameters

Send either the canonical name or the native name, not both. Canonical names

NameType DefaultAllowed Description
promptrequired
Typestring
Prompt that guides image generation.
seedoptional
Typeinteger | null
Generation seed override; omitting it lets generation choose a seed at random.
num_inference_stepsoptional
Typeinteger
Default4
4 – 8
Count of inference steps to run.
image_sizeoptional
Typeobject
Defaultlandscape_4_3
square_hdsquareportrait_4_3portrait_16_9landscape_4_3landscape_16_9
Dimensions for the image being generated.
num_imagesoptional num_outputs
Typeinteger
Default1
1 – 4
Image count requested for generation.
enable_safety_checkeroptional
Typeboolean
Defaulttrue
Safety checking, which returns black images in place of any images flagged unsafe. A value of true enables checking; false disables it only for authorized accounts, while requests without authorization are checked regardless.
output_formatoptional
Typeenum
Defaultpng
jpegpngwebp
File format for the resulting image.
required Canonical name, also accepted

Output

GET /requests/req_8k2m4q7x1z9c3v5b6n0p2r4t
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "flux-2/klein/4b",
  "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": 5,
    "usd": "0.005",
    "charged": 5,
    "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.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
Your files, your choiceEvery outputs[].url is a copy on our storage: kept forever (paid per GB-month) or 7 days for free, by your account setting or ?storage=.
Same shape on every modeltype, url, content_type, width, height and duration, for images, video and audio alike. output is the model’s own result object.
Fields of output
images
array of object {url, content_type, file_name, file_size, width, height}Images produced by the model.
timings
object
seed
integerImage-generation seed, including the randomly chosen value if the input omitted a seed; otherwise, it repeats the supplied value.
has_nsfw_concepts
array of booleanIndicates whether NSFW concepts appear in the generated images.
prompt
stringPrompt used during image generation.

More models: Text to Image

For AI agents: this page as Markdown is at https://doitong.com/developers/models/flux-2/klein/4b.md. All models and guides: https://doitong.com/developers/llms.txt