API reference · BFL

bfl/flux-3/video-extend

Integrate this model through SandBase's unified API, with production-ready schemas and examples.

VIDEOAsyncOpen model

Production endpoint

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OpenAI-compatible endpoint with unified authentication and usage tracking.

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

Model IDbfl/flux-3/video-extend

Input Schema

6 parameters · 2 required · 4 optional

Parameter	Type	Required	Description
`video`	string	Required	URL of the input video. MP4, under 50 MB and under 15 seconds.
`prompt`	string	Required	The text prompt describing how the video continues from the source clip's final frames.
`duration`	integer	Optional	Seconds of new footage to add after the source video (5-20). · Options: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 · Default: 5 567891011121314151617181920
`resolution`	string	Optional	Resolution of the generated video. · Options: 720p, 1080p · Default: "720p" 720p1080p
`aspect_ratio`	string	Optional	Output aspect ratio. Follows the input when omitted. · Options: 21:9, 2:1, 16:9, 4:3, 1:1, 3:4, 9:16 21:92:116:94:31:13:49:16
`generate_audio`	boolean	Optional	Whether to generate audio for the video. · Default: true

Output Schema

Field	Type	Description
`id`	string	Unique identifier for the generation task
`status`	string	Task status: pending, running, completed, failed, timeout
`model`	string	Model used for the generation
`outputs`	array	Array of output items
`outputs[].url`	string	URL of the generated artifact
`outputs[].content_type`	string	MIME type (e.g. image/png, video/mp4)
`error`	object \| null	Error details if failed, null on success
`error.type`	string	Machine-readable error type code
`error.message`	string	Human-readable error description

Async Workflow

This model uses asynchronous execution. Submit a request and poll for the result.

Submit — POST to /v1/run, receive an id
Poll — GET /v1/run/{id} until status is completed, failed, or timeout
Retrieve — Read outputs from the completed response

Code Examples

Ready-to-run snippets

const apiKey = process.env.SANDBASE_API_KEY;
const response = await fetch("https://api.sandbase.ai/v1/run", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${apiKey}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "bfl/flux-3/video-extend",
    "video": "https://storage.googleapis.com/falserverless/example_inputs/flux-3-red-panda.mp4",
    "prompt": "The camera keeps tracking as the subject turns and smiles.",
    "duration": 5,
    "resolution": "720p",
    "generate_audio": true
  }),
});

if (!response.ok) throw new Error(await response.text());
let result = await response.json();
for (let attempt = 0; attempt < 120 && !["completed", "failed", "timeout"].includes(result.status); attempt++) {
  await new Promise((resolve) => setTimeout(resolve, 2_000));
  const poll = await fetch(`https://api.sandbase.ai/v1/run/${result.id}`, {
    headers: { Authorization: `Bearer ${apiKey}` },
  });
  if (!poll.ok) throw new Error(await poll.text());
  result = await poll.json();
}
if (result.status !== "completed") throw new Error(`Generation ended: ${result.status}`);
console.log(result);

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