Flux 2 Klein 9B Text to Image

bfl/flux-2/klein/9b

Flux 2 Klein 9b is BFL's advanced text-to-image AI model. Create photorealistic images, illustrations, and concept art from natural language descriptions with exceptional detail and prompt adherence.

Try the model

Playground

Open playground

Input

Prompt(string)

The prompt to generate an image from.

Additional Settings More

Customize your input with more control.

Number of Inference Steps(integer)

The number of inference steps to perform. Range: 4 to 8.

Output Format(string)

The format of the generated image. Allowed values: jpeg, png.

Aspect Ratio(string)

The aspect ratio of the generated image. Allowed values: 21:9, 16:9, 3:2, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 9:16.

Seed(integer)

The seed to use for the generation. If not provided, a random seed will be used.

Result

Example

What would you like to do next?
Open original

Examples

Select an example to load its inputs and result into the playground.

Input
```
{
  "prompt": "A bright, surreal scene on a vast white salt flat under a clear blue sky, featuring two fluffy white alpacas standing in the foreground. Behind them sits a sleek white supercar with its scissor doors open, creating a dramatic futuristic silhouette. The sunlight is strong and crisp, casting sharp shadows on the ground and giving the image a clean, high-contrast cinematic look. Minimalist composition, playful luxury vibe, ultra sharp detail, wide-angle perspective, high resolution."
}
```
Open result ↗

Human preference

Arena

Elo ratings from blind side-by-side votes, compared with other image and video models.

Rankings sourced from Artificial Analysis Arena

Leaderboard: Text to Image
Rank: #76 of 106
Elo: 929 ±10
Gap to #1: −293

Text-to-image arena: people pick the better of two images generated from the same prompt, without seeing the model names.

#71Z-Image TurboAlibabaOn SandBase936±11
#72GPT Image 1 Mini (medium)OpenAI936±17
#73HunyuanImage 3.0TencentOn SandBase932±16
#74Dreamina 3.1Bytedance931±17
#75FLUX.1 Kontext [max]Black Forest Labs929±12
#76FLUX.2 [klein] 9BBlack Forest LabsThis model929±10
#77Kling Image 3.0 OmniKlingAIOn SandBase918±17
#78FLUX.1 Kontext [pro]Black Forest Labs917±18
#79ERNIE Image TurboBaidu914±10
#80Ideogram 3.0IdeogramOn SandBase911±18

Flux 2 Klein 9B Text to Image

FLUX.2 [klein] 9B, a compact open model for fast, low-cost images. Text to image.

Fields

Field	Type	Default	Notes
`prompt`	string, required	—	Text instruction.
`num_inference_steps`	integer 4–8	4	More steps add detail and time.
`output_format`	`jpeg` / `png`	`png`	Output file format.
`aspect_ratio`	`21:9` / `16:9` / `3:2` / `4:3` / `5:4` / `1:1` / `4:5` / `3:4` / `2:3` / `9:16`	`16:9`	Output shape.
`seed`	integer	random	Fix it to compare prompt changes.

Billing

$0.01 per image.

Request	Price
One image	$0.01

Failed runs are not charged.

Prompting

Write subject, setting, composition, style, then light.
Quote any text that must appear.

Limits

One output image per request.

Also on SandBase

Other FLUX.2 endpoints: bfl/flux-2/max, bfl/flux-2/pro, bfl/flux-2/flex, bfl/flux-2/dev, bfl/flux-2/klein/9b/edit.

Start building

Send your first request

Submit this model through the SandBase Unified Run API.

Production API

Unified Run API endpoint

https://api.sandbase.ai/v1/run

Model ID

bfl/flux-2/klein/9b

# The quoted heredoc keeps Unicode and shell metacharacters unchanged.
result=$(curl --fail-with-body --silent \
  -X POST "https://api.sandbase.ai/v1/run" \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'SANDBASE_JSON'
{
  "model": "bfl/flux-2/klein/9b",
  "prompt": "A bright, surreal scene on a vast white salt flat under a clear blue sky, featuring two fluffy white alpacas standing in the foreground. Behind them sits a sleek white supercar with its scissor doors open, creating a dramatic futuristic silhouette. The sunlight is strong and crisp, casting sharp shadows on the ground and giving the image a clean, high-contrast cinematic look. Minimalist composition, playful luxury vibe, ultra sharp detail, wide-angle perspective, high resolution.",
  "aspect_ratio": "16:9",
  "output_format": "png",
  "num_inference_steps": 4
}
SANDBASE_JSON
)
run_id=$(printf '%s' "$result" | jq -r .id)
for attempt in $(seq 1 120); do
  status=$(printf '%s' "$result" | jq -r .status)
  case "$status" in completed|failed|timeout) break ;; esac
  sleep 2
  result=$(curl --fail-with-body --silent \
    -H "Authorization: Bearer $SANDBASE_API_KEY" \
    "https://api.sandbase.ai/v1/run/$run_id")
done
status=$(printf '%s' "$result" | jq -r .status)
[ "$status" = completed ] || { echo "Generation ended: $status" >&2; exit 1; }
printf '%s\n' "$result"

2. Authentication

Create a SandBase API key and set it in your server environment. All requests use Bearer authentication.

API key environment variable

export SANDBASE_API_KEY="YOUR_API_KEY"

Keep the key on your server. Do not expose it in browser code or commit it to a repository.

3. Queue

Submit a request

POST to /v1/run with this model ID and its inputs. The request example above includes submission and polling.

Fetch request status and result

Use the returned run ID to poll until the status is completed, failed or timeout. Read output only after completed.

Poll run status

curl "https://api.sandbase.ai/v1/run/$RUN_ID" \
  -H "Authorization: Bearer $SANDBASE_API_KEY"

4. Files

Hosted files

Pass a publicly accessible file URL in the model’s image, video or audio field. Supported formats and limits are shown beside each Playground input.

Uploading images

Use the upload or replace control on supported image fields in the Playground. Video URL fields accept a hosted driving video; they do not imply video-upload support.

5. Schema

Input

`seed`integer

The seed to use for the generation. If not provided, a random seed will be used.

`prompt`stringrequired

The prompt to generate an image from.

`aspect_ratio`string

The aspect ratio of the generated image.

Default: "16:9"

Possible values: "21:9", "16:9", "3:2", "4:3", "5:4", "1:1", "4:5", "3:4", "2:3", "9:16"

`output_format`string

The format of the generated image.

Default: "png"

Possible values: "jpeg", "png"

`num_inference_steps`integer

The number of inference steps to perform.

Default: 4

Minimum: 4

Maximum: 8

Request body

{
  "model": "bfl/flux-2/klein/9b",
  "prompt": "A bright, surreal scene on a vast white salt flat under a clear blue sky, featuring two fluffy white alpacas standing in the foreground. Behind them sits a sleek white supercar with its scissor doors open, creating a dramatic futuristic silhouette. The sunlight is strong and crisp, casting sharp shadows on the ground and giving the image a clean, high-contrast cinematic look. Minimalist composition, playful luxury vibe, ultra sharp detail, wide-angle perspective, high resolution.",
  "aspect_ratio": "16:9",
  "output_format": "png",
  "num_inference_steps": 4
}

Output

A completed run exposes its result in output. The following is the model’s saved example, not a new generation.

Example output JSON

[
  {
    "source": "BFL/FLUX schema mirror",
    "source_url": "https://docs.bfl.ai/flux_2/flux2_overview",
    "url": "https://static.sandbase.ai/examples/5417ffc5-c412-4ec7-a005-f1be7373e7d4/output/9dfc2f6f-d98e-4e89-b7d2-cc2f89ecc5b5.png"
  }
]

Flux 2 Klein 9B Text to Image

Playground

Examples

Arena

Flux 2 Klein 9B Text to Image

Fields

Billing

Prompting

Limits

Also on SandBase

Send your first request

2. Authentication

3. Queue

Submit a request

Fetch request status and result

4. Files

Hosted files

Uploading images

5. Schema

Input

seedinteger

promptstringrequired

aspect_ratiostring

output_formatstring

num_inference_stepsinteger

Output

Flux 1 Schnell ↗

Flux 2 Dev Text to Image ↗

Flux 2 Flash Text to Image ↗

Flux 2 Flex Text to Image ↗

Flux 2 Klein 4B Text to Image ↗

Flux 2 Max Text to Image ↗

`seed`integer

`prompt`stringrequired

`aspect_ratio`string

`output_format`string

`num_inference_steps`integer