Flux 3 Video

flux-3-video is a Black Forest Labs video model. Create a task, then poll it. When it completes, read the returned url, or download the video with GET /v1/videos/{id}/content.

POST /v1/videos
GET /v1/videos/{task_id}

Only full renders are supported. Billing is per second and is the same on the standard and official groups. Omit any field you are not setting. Image and video inputs must be public URLs that stay reachable until the task finishes.

Pricing

Resolution	No video input	With video input
720p	¥1.32 / second	¥1.848 / second
1080p	¥2.112 / second	¥2.376 / second

Video input means input_reference only. A first frame, last frame, or keyframe in images does not change the per-second price.

Request fields

Field	Required	Type	Range	Description
`model`	yes	string	`flux-3-video`	Fixed model ID
`prompt`	no	string	—	Scene description. If omitted, provide a first frame or `input_reference`
`resolution`	yes	string	`720p`, `1080p`, or width x height	`720p` is 1280x720 and `1080p` is 1920x1080. A width x height value is classified by its short side. Omitted requests use 720p
`duration`	yes	integer	5–20	Integer seconds. `seconds` may be sent as an integer string instead. Values outside 5–20 are rejected
`image`	no	string	—	First frame. Do not send it with `input_reference`
`end_frame`	no	string	—	Last frame. Rejected when there is no first frame. Do not send it with `input_reference`
`images`	no	array	1–10	Keyframes. One image is the start, two images are the start and end, and more images are spaced evenly. Do not send them with `input_reference`
`input_reference`	no	string	mp4	One video to continue. This selects the with-video price. Do not send it with images
`aspect_ratio`	no	string	`21:9`, `2:1`, `16:9`, `4:3`, `1:1`, `3:4`, `9:16`	If omitted, the picture decides the ratio
`audio`	no	boolean	—	Audio is generated when omitted. Send `false` to disable it
`safety_tolerance`	no	integer	0–4	Content tolerance

Text to video

curl https://kaienapi.com/v1/videos \
  -H "Authorization: Bearer <YOUR_API_KEY>" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "flux-3-video",
    "prompt": "a red circle moving across a lake",
    "resolution": "720p",
    "duration": 5
  }'

Creation returns a task, not the video file:

{
  "id": "task_example",
  "object": "video",
  "model": "flux-3-video",
  "status": "queued"
}

First and last frames

The first item in images is the opening frame. The second item is the closing frame.

curl https://kaienapi.com/v1/videos \
  -H "Authorization: Bearer <YOUR_API_KEY>" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "flux-3-video",
    "prompt": "a smooth transition from the first frame to the last frame",
    "images": [
      "https://example.com/first.jpg",
      "https://example.com/last.jpg"
    ],
    "resolution": "720p",
    "duration": 5
  }'

Polling

Poll with the task ID from the create response. Keep polling while status is queued or in_progress, until it is completed or failed.

curl "https://kaienapi.com/v1/videos/$TASK_ID" \
  -H "Authorization: Bearer <YOUR_API_KEY>"

Completed response:

{
  "id": "task_example",
  "object": "video",
  "model": "flux-3-video",
  "status": "completed",
  "url": "<file url>"
}

Field	Type	Description
`id`	string	Task ID. Query it with `GET /v1/videos/{id}`
`status`	string	`queued`, `in_progress`, `completed`, or `failed`
`url`	string	Completed file URL

The video bytes can also be downloaded:

curl "https://kaienapi.com/v1/videos/$TASK_ID/content" \
  -H "Authorization: Bearer <YOUR_API_KEY>" \
  --output result.mp4

Getting started

Images and video

Audio

AI tools

API Reference

Pricing

Request fields

Text to video

First and last frames

Polling

​Pricing

​Request fields

​Text to video

​First and last frames

​Polling

Pricing

Request fields

Text to video

First and last frames

Polling