YouTube Shorts max out at 1080p, so don't generate at 4K

For a YouTube Short, set the resolution to 1080p. YouTube's Shorts help says you can upload Shorts with a maximum resolution of 1080p, up to 3 minutes (read 2026-10-07). Sume's Gemini Omni Flash 1.1 can render 3-10 seconds at 360p, 720p, 1080p, or 4K, in 16:9 or 9:16, so the 4K setting is a tier your Short cannot use.

Price differs by resolution in the Sume catalog, so choosing 1080p is also the cheaper of the two top tiers. I give no price here: read GET /v1/videos/models for the live numbers.

What each side offers

From YouTube's Shorts help and Sume's Video Router docs.

Request 1080p at 9:16

The Video Router takes resolution plus aspect_ratio, not a size string (the v1 models list no supported sizes, and size returns 400 unsupported_parameter). Send an Idempotency-Key and poll the job.

curl -X POST https://api.sume.com/v1/video-router/generate \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: short-1080p-001" \
  -d '{
    "model": "gemini-omni-flash-1.1",
    "prompt": "A vertical product clip on a desk, natural light",
    "resolution": "1080p",
    "duration": 8,
    "aspect_ratio": "9:16",
    "mode": "async"
  }'

What the page does not say

The help page states a maximum; it does not say what YouTube does to a larger file, whether it downscales or refuses it, so do not assume either. The safe move is to not produce one.

A 3-minute Short needs more than one clip, because each model caps a single clip at 30 seconds or fewer. Assemble in Timeline 1.0 at 1080x1920 (the default), which is within the 2160 per-side limit by a wide margin.

A resolution ladder for drafts

Draft cheap, finalize at 1080p. Generate ideas at 360p or 720p on Omni Flash, pick the winners, and re-run only those at 1080p. The ladder stops at 1080p for Shorts; a 4K run would be a cost with no destination on this platform.

If the same clip is also headed to a 4K display or a client deck, 4K may be worth it for that file, but it is a different deliverable. Export the Short at 1080p and keep the 4K copy for the deck, rather than uploading the larger file.