black-forest-labs/flux-3/video-extend

black-forest-labs/flux-3/video-extend

FLUX 3 Video Extend continues input videos into new 5-20 second clips, using prompt guidance to control the next action, camera movement, visual style, motion continuity, and optional synchronized audio at 720P / 1080P output. Ready-to-use REST inference API, best performance, no coldstarts, affordable pricing.

Examples

black-forest-labs/flux-3/video-extend Examples 1

Parameters

NameTypeDefaultConstraintsDescription
prompt *Prompttextarea—≤ 5000 charsThe text prompt describing the video you want to generate.
aspect_ratioAspect Ratioselect—21:9 | 2:1 | 16:9 | 4:3 | 1:1 | 3:4 | 9:16The aspect ratio of the generated media.
resolutionResolutionselect720p720p | 1080pResolution of the generated video.
durationDurationslider55 ~ 20 · step 1Video length in seconds (5-20).
generate_audioGenerate Audiobooleantrue—Whether to generate audio for the video.

Output fields

FieldTypeDescription
videosarray<string>

API

Call this model through one unified REST API. Get a key on the API Keys page.

cURL
# 1) Submit — returns { "task_uuid": "..." }
curl -X POST "https://www.namifusion.com/api/v1/marketplace/run/black-forest-labs/flux-3/video-extend" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "input": {
    "prompt": "Continue the scene naturally, preserving the subjects, setting, lighting and motion of the input video.",
    "aspect_ratio": "16:9",
    "resolution": "720p",
    "duration": 5,
    "generate_audio": true
  }
}'

# 2) Poll until status is "completed", then read the output URLs
curl "https://www.namifusion.com/api/v1/marketplace/run/tasks/TASK_UUID" \
  -H "Authorization: Bearer YOUR_API_KEY"
Python
import time, requests

API_KEY = "YOUR_API_KEY"
HEADERS = {"Authorization": f"Bearer {API_KEY}"}

# 1) Submit
resp = requests.post(
    "https://www.namifusion.com/api/v1/marketplace/run/black-forest-labs/flux-3/video-extend",
    headers=HEADERS,
    json={
        "input": {
            "prompt": "Continue the scene naturally, preserving the subjects, setting, lighting and motion of the input video.",
            "aspect_ratio": "16:9",
            "resolution": "720p",
            "duration": 5,
            "generate_audio": True
        }
    },
)
resp.raise_for_status()  # 401/402/429/5xx stop here instead of polling a bad task
task = resp.json()

# 2) Poll until a terminal state (completed / failed / cancelled).
#    This model is allowed up to 1800s server-side.
deadline = time.time() + 1860
while task.get("status") not in ("completed", "failed", "cancelled"):
    if time.time() > deadline:
        raise TimeoutError(f"still {task.get('status')} — keep the task_uuid and poll later")
    time.sleep(3)
    poll = requests.get(f"https://www.namifusion.com/api/v1/marketplace/run/tasks/{task['task_uuid']}", headers=HEADERS)
    poll.raise_for_status()
    task = poll.json()

print(task["status"], task.get("output"))
JavaScript
const API_KEY = "YOUR_API_KEY";
const HEADERS = { Authorization: `Bearer ${API_KEY}` };

// 1) Submit
const resp = await fetch("https://www.namifusion.com/api/v1/marketplace/run/black-forest-labs/flux-3/video-extend", {
  method: "POST",
  headers: { ...HEADERS, "Content-Type": "application/json" },
  body: JSON.stringify({
    "input": {
      "prompt": "Continue the scene naturally, preserving the subjects, setting, lighting and motion of the input video.",
      "aspect_ratio": "16:9",
      "resolution": "720p",
      "duration": 5,
      "generate_audio": true
    }
  }),
});
if (!resp.ok) throw new Error(`submit failed: ${resp.status} ${await resp.text()}`);
let task = await resp.json();

// 2) Poll until a terminal state (completed / failed / cancelled).
//    This model is allowed up to 1800s server-side.
const deadline = Date.now() + 1860 * 1000;
while (!["completed", "failed", "cancelled"].includes(task.status)) {
  if (Date.now() > deadline) throw new Error(`still ${task.status} — keep the task_uuid and poll later`);
  await new Promise((r) => setTimeout(r, 3000));
  const poll = await fetch(`https://www.namifusion.com/api/v1/marketplace/run/tasks/${task.task_uuid}`, { headers: HEADERS });
  if (!poll.ok) throw new Error(`poll failed: ${poll.status}`);
  task = await poll.json();
}

console.log(task.status, task.output);

Documentation

black-forest-labs/flux-3/video-extend

black-forest-labs/flux-3/video-extend

FLUX 3 Video Extend continues input videos into new 5-20 second clips, using prompt guidance to control the next action, camera movement, visual style, motion continuity, and optional synchronized audio at 720P / 1080P output. Ready-to-use REST inference API, best performance, no coldstarts, affordable pricing.

Parameters

ParameterTypeRequiredDefaultLimits / description
promptstringYes—max 5000 chars; The text prompt describing the video you want to generate.
videostringYes—URL of the input video. MP4, under 50 MB and under 15 seconds.
aspect_ratiostringNo—21:9, 2:1, 16:9, 4:3, 1:1, 3:4, 9:16; The aspect ratio of the generated media.
resolutionstringNo"720p"720p, 1080p; Resolution of the generated video.
durationintegerNo55–20; step 1; Video length in seconds (5-20).
generate_audiobooleanNotrueWhether to generate audio for the video.

Pricing

ModeUSD / secondCredits / secondUSD / 5 seconds
720p$0.4141$2.05
1080p$0.5353$2.65

Price = rate × min(ceil(duration), 20). duration is an integer from 5 to 20; default 5. generate_audio does not change the price. Billing uses requested extension duration, not the input video duration.

WaveSpeed standard list price; USD 1 = 100 credits. Account discounts are separate.

API

curl -X POST https://www.namifusion.com/api/v1/marketplace/run/black-forest-labs/flux-3/video-extend \
  -H "Authorization: Bearer $API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "input": {
    "prompt": "Continue the scene naturally, preserving the subjects, setting, lighting and motion of the input video.",
    "video": "https://assets-public.namifusion.com/marketplace/videos/2026-04-14/88d6efad3763.mp4",
    "aspect_ratio": "16:9",
    "resolution": "720p",
    "duration": 5,
    "generate_audio": true
  }
}'
curl 'https://www.namifusion.com/api/v1/marketplace/run/tasks/TASK_UUID' \
  -H "Authorization: Bearer $API_KEY"

Submit returns task_uuid. Poll until completed or failed. Successful output: output.videos (URL array). This API is asynchronous and returns URLs.

WaveSpeed

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