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FLUX 3 Draft Extend Video: Fast Clip Continuation Drafts on Models and API | RunComfy

blackforestlabs/flux-3/extend-video/draft

FLUX 3 Draft Extend Video continues a source clip into a fast 720p draft, with a reusable cache for later full-quality enhancement.

The text prompt describing the draft video.
URL or data URI of the source MP4, at most 50 MiB.
Aspect ratio of the generated draft. auto lets the model choose.
Draft duration in whole seconds from 5 through 20, or auto.
Whether to generate audio for the draft video.
The safety tolerance level for the generated video. 0 is the strictest and 4 is the most permissive.
Idle
The rate is $0.132 per second of generated draft video (720p).

Introduction To FLUX 3 Draft Extend Video

Black Forest Labs' FLUX 3 Draft Extend Video continues an existing clip into a fast 720p preview from a written brief, built for cheap continuation trials before a full-quality pass. Trading expensive final-quality reruns for quick extend checks while keeping a reusable draft cache for later enhancement, FLUX 3 Draft Extend Video helps marketers, editors, and previz artists iterate without burning budget. For developers, FLUX 3 Draft Extend Video on RunComfy can be used both in the browser and via an HTTP API, so you don't need to host or scale the model yourself.
Ideal for: Clip Continuation Drafts | Low-Cost Extend Tests | Storyboard Tail Previews

Black Forest Labs / FLUX 3 Draft Extend Video#


This page covers the extend-video draft endpoint in the FLUX 3 family. You provide a source MP4 and describe how the shot should continue; the model returns a quick 720p continuation so you can validate the next beat without paying full FLUX 3 Extend Video rates.


The endpoint is built for the early loop of editorial work: continuation prompt tests, duration trials, and batch draft extends. When a take looks right, reuse the returned draft cache with draft-enhance for a fuller finish.

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Frequently Asked Questions

What is FLUX 3 Draft Extend Video best used for?

FLUX 3 Draft Extend Video continues an existing MP4 into a fast 720p preview from a written brief. It fits continuation trials, editorial tail tests, and high-volume draft extends where cost matters more than final sharpness.

How does FLUX 3 Draft Extend Video differ from full FLUX 3 Extend Video?

Both continue from a source clip; FLUX 3 Draft Extend Video returns a cheaper 720p preview plus a reusable draft cache, while the full endpoint is better for polished 720p or 1080p deliverables.

What inputs, duration, and aspect ratios does FLUX 3 Draft Extend Video support?

FLUX 3 Draft Extend Video requires a prompt and a source video URL (MP4, at most 50 MiB). Duration can be auto or 5–20 seconds, with aspect ratios auto, 21:9, 2:1, 16:9, 4:3, 1:1, 3:4, and 9:16.

What is the draft cache from FLUX 3 Draft Extend Video used for?

Along with the preview clip, FLUX 3 Draft Extend Video returns a reusable draft cache you can pass to draft-enhance for a fuller-quality render without rebuilding the continuation from scratch.

Does FLUX 3 Draft Extend Video need start or end still images?

No. FLUX 3 Draft Extend Video is video-to-video: the source clip anchors the final frames, and the prompt guides how the shot continues. For still-driven drafts, use other FLUX 3 draft modes.

Can developers call FLUX 3 Draft Extend Video through the RunComfy API after trying it in the UI?

Yes. Prototype in the RunComfy model UI, then call the same FLUX 3 Draft Extend Video template through the RunComfy API with matching parameters. Generations consume usd / credits on both paths.

How much does FLUX 3 Draft Extend Video cost on RunComfy?

FLUX 3 Draft Extend Video is billed at $0.132 per second of generated draft video at 720p. A 5-second continuation costs about $0.66; longer outputs scale with the generated length.

When should I stay on FLUX 3 Draft Extend Video versus full quality?

Stay on FLUX 3 Draft Extend Video for continuation drafts and early editorial reviews. Move to full FLUX 3 Extend Video or draft-enhance when you need sharper finals for ads or client delivery.

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Examples Of FLUX 3 Draft Extend Video

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