Wan 3.0 Pro Prime · Video Extend

Tacking length onto a finished clip is the least glamorous task in video generation and one of the most useful. This node continues a clip you already have - the new segment opens on its last frame and comes back joined on, so there's no assembly step, no second loader, no stitching graph.

At Pro Prime rates, from 35.1 credits ($0.351) per second, with the source clip free. Two things follow from that. First, it's the most expensive way in this pack to add seconds to a shot, so it's the right choice only when the footage you're extending already came from this tier - you don't want a Prime segment butted against a 480p base-tier source, for sharpness reasons the tooltip itself warns about. Second, extending is much cheaper than regenerating, so if the first twenty seconds are good, this is the sane way to keep them.

And it's cloud-only, like all of Wan 3.0.

How it works

Feed a ComfyUI VIDEO into video_url - output from a video loader, a previous generation, whatever. The pack remuxes MP4 sources without re-encoding and uploads them, with a 90 MiB per-file limit; sources can be MP4, MOV or WebM up to 60 seconds. Then the usual: quote before credits are held, task submitted under an idempotency key, progress printed on the node, result downloaded as a single VIDEO containing your original plus the new segment.

The mechanic worth understanding is that the seam quality comes from two things you control - the resolution you generate the new segment at, and how well your prompt describes a continuation rather than a new scene.

The inputs that matter

video_url - the clip to continue. Its final frame is the opening frame of the new segment, so if the last moment of your source is blurred or mid-whip-pan, the extension inherits that.

prompt - what happens next: the action that follows and the camera move. Write forwards. Describing the whole scene again tends to produce a hard cut rather than a continuation.

resolution - 1080p, 2k or 4k for the new segment, with the family's standing disclosure that native rendering tops out at 1080p and the top tiers are enlarged. Match your source; a mismatch shows up at the join even when the motion is seamless.

duration_seconds - 2 to 30, or -1 to let the model pick a length. The source clip is added on top of that and isn't billed, so a 15-second source plus a 30-second extension gives you a 45-second result and you pay for thirty.

generate_audio generates sound for the new segment; the source keeps its own sound regardless. Extend a silent clip with audio on and you'll get an audible change at the seam, which may or may not be what you want.

last_image_url - optional target end frame for the new segment. This is the field that turns extension into shot design: the opening frame comes from your clip, the closing frame from a still you supply, and the model fills what's between.

Outputs: video and task id.

Installing it

cd ComfyUI/custom_nodes
git clone https://github.com/popnow-ai/popnow-comfyui

or install from Manager by searching PopNow. Restart, add a key from popnow.ai/api/console/keys in Settings > PopNow (or set POPNOW_API_KEY), restart again. No models, no dependencies beyond ComfyUI, no GPU. Delete custom_nodes/popnow_api.py if you're upgrading from the old single-file node.

Where people get burned

Chaining. Extend twice and the accumulated drift is visible; extend four times and it's the story. Better pattern: generate a fresh clip with last_image_url matching the previous ending, which resets the model's context instead of compounding it.

Also watch what you're actually paying for. The node doesn't charge for the source, but it does charge 35 credits a second for the new segment, and a 30-second extension at 4K is over a thousand credits for a resize you could do yourself. Set Settings > PopNow > Max credits per run so the quote gate can stop you before anything is held.

Codes: 40201 no credits, 40004 unsupported combination with the field named, 400 rejected value, 40310 unverified email. Refused runs are refunded; interrupted runs are not cancelled - the task finishes on PopNow and settles if it succeeds. Uploads over 90 MiB stop you earlier: trim the source rather than fight it.