Image model by Black Forest Labs
FLUX.2 Klein 4B API
model: flux-2-klein-4b
Call FLUX.2 Klein 4B with your KeelRouter API key, the same key you use for every other model. From $0.006 per image, paid per call from a prepaid balance. Failed calls are free.
Pricing
| Option | Price |
|---|---|
| per image | $0.006 per image |
Call it
Async: POST /v1/images/generations returns a taskId; poll the same path with ?task_id= or pass a callback_url.
curl https://api.keelrouter.com/v1/images/generations \
-H "Authorization: Bearer $KEELROUTER_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "flux-2-klein-4b",
"prompt": "A lighthouse at dawn, watercolor"
}'Parameters
| Name | Type | Notes |
|---|---|---|
| model | string | Required. flux-2-klein-4b |
| prompt | string | Required. |
| image_urls | array | |
| aspect_ratio | string | One of 1:1, 16:9, 9:16, 3:2, 2:3, 4:3, 3:4, 5:4, 4:5, 21:9, 9:21, match_input_image. Default 1:1. |
| output_format | string | One of jpg, png, webp. Default jpg. |
| seed | number | |
| callback_url | string | Optional https URL; we POST the result when the task ends |
FAQ
- How much does the FLUX.2 Klein 4B API cost on KeelRouter?
- From $0.006 per image. You pay per call from a prepaid USD balance; failed calls are not charged.
- How do I call FLUX.2 Klein 4B?
- POST to /v1/images/generations with model "flux-2-klein-4b". You get a taskId back; poll the same endpoint with ?task_id= or pass a callback_url.
- Is this the official FLUX.2 Klein 4B API?
- No. KeelRouter is an independent API gateway. Requests run on FLUX.2 Klein 4B through our upstream providers, and the image model keeps its own safety filters.
- How long are results kept?
- Result files are kept for 30 days, then deleted. Download what you want to keep.
KeelRouter is an independent service and is not affiliated with Black Forest Labs. FLUX.2 Klein 4B is a trademark of its owner, used here only to name the model a request runs on.