How to Use the black-forest-labs/flux-3/video-extend-draft API: video to video integration guide (2026)
Learn how to call the black-forest-labs/flux-3/video-extend-draft API on NamiFusion: parameters, pricing (from ≈$0.600) and runnable copy-paste code — try it in the playground first.
black-forest-labs/flux-3/video-extend-draft is a video to video model by Black Forest Labs: FLUX 3 Video Extend Draft quickly continues a required input video into a draft clip with prompt-guided next-scene motion, optional synchronized audio, and flexible 5-20 second duration for rapid iteration. On NamiFusion you can try it in the playground (exact quote shown before you submit), then call it through one unified REST API — about $0.600 per typical run.
TL;DR
· Task type: video to video, provided by Black Forest Labs
· Pricing: about $0.600 per typical run ($1 = 100 credits), pay-as-you-go
· Getting started: playground (exact quote before submit) → create an API key → one POST request
· Tunable parameters: 4 (see the table below)
· No platform watermark; commercial use allowed (per the Terms of Service)
What can you build with black-forest-labs/flux-3/video-extend-draft?
Short-form video and ad clips: go from a prompt or a single image to publishable motion content.
Product demos and concept previews: validate storyboards and visual direction cheaply before any shoot.
A social content factory: batch vertical clips and ride trending topics fast.
Remixing existing assets: image-to-video brings static work to life and extends its lifespan.
How do you call this API?
- Sign up on NamiFusion and create a key on the API Keys page (signup bonus credits can only be used on selected models).
- Submit a task with the cURL example below, passing your key as a Bearer token.
- Poll the task status with the returned task_uuid and read the output URLs when completed.
# 1) Submit — returns { "task_uuid": "..." }
curl -X POST "https://www.namifusion.com/api/v1/marketplace/run/black-forest-labs/flux-3/video-extend-draft" \
-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",
"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"What parameters does it take?
prompt (Prompt): required
aspect_ratio (Aspect Ratio): optional
duration (Duration): optional, default 5
generate_audio (Generate Audio): optional, default true
How do you write prompts for black-forest-labs/flux-3/video-extend-draft?
- Subject first: lead with the actor and action, then add environment, lighting and style ("an astronaut sprinting through a neon street in the rain, cinematic, shallow depth of field").
- Concrete nouns beat stacked adjectives: "85mm portrait lens, golden-hour backlight" works far better than "very beautiful, ultra high quality".
- Change one variable per iteration: pin the seed to reproduce a result, tweak a single phrase at a time so you know what actually moved the output.
- State negatives positively: instead of "no blur", ask for "sharp focus, crisp details".
How much does it cost?
Pay-per-use in credits. About $0.600 per typical run ($1 = 100 credits); the exact price varies with parameters like resolution or duration, and the playground shows the exact quote before you submit.
black-forest-labs/flux-3/video-extend-draft
black-forest-labs/flux-3/video-extend-draft
FLUX 3 Video Extend Draft quickly continues a required input video into a draft clip with prompt-guided next-scene motion, optional synchronized audio, and flexible 5-20 second duration for rapid iteration.
Parameters
| Parameter | Type | Required | Default | Limits / description |
|---|---|---|---|---|
prompt | string | Yes | — | max 5000 chars; The text prompt describing the video you want to generate. |
video | string | Yes | — | URL of the input video. MP4, under 50 MB and under 15 seconds. |
aspect_ratio | string | No | — | 21:9, 2:1, 16:9, 4:3, 1:1, 3:4, 9:16; The aspect ratio of the generated media. |
duration | integer | No | 5 | 5–20; step 1; Video length in seconds (5-20). |
generate_audio | boolean | No | true | Whether to generate audio for the video. |
Pricing
| Mode | USD / second | Credits / second | USD / 5 seconds |
|---|---|---|---|
| Draft | $0.12 | 12 | $0.6 |
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-draft \
-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",
"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.
FAQ
Can I try it for free first?+
Signup bonus credits can only be used on selected models, and eligibility may change. The playground shows the exact quote before submission.
Can I use the output commercially? Is there a watermark?+
Yes, outputs are yours to use commercially, and NamiFusion adds no platform watermark — subject to the Terms of Service and applicable law.
What is the content policy?+
Pornographic content, sexualized content involving a minor, unauthorized use of real people, deceptive impersonation, fraud and false endorsements are prohibited. Lawful, consensual, non-explicit adult themes may be permitted; see the Terms of Service.
How long does a black-forest-labs/flux-3/video-extend-draft task take?+
It depends on parameters — images usually take seconds, videos tens of seconds to minutes. The API returns a task_uuid for polling.
What are the resolution and duration limits?+
See the parameter table above — each model lists its available resolution and duration options there and in the playground.