YouTube end screens need a 25-second video: plan the clip length

YouTube's upload documentation says end screens need a video that is 25 seconds or longer. A single clip from most Sume video models will not reach that, so either choose a model with a 30-second ceiling or assemble several clips with Timeline.

What YouTube states

The YouTube upload page, read on 2026-10-03, lists the limits relevant to a batch.

Which Sume models reach 25 seconds

The video docs state per-model duration ranges. seedance-2.5 accepts 4 to 30 seconds, wan-3.0 accepts 2 to 30 seconds, higgsfield-genjutsu (Motion Transfer) accepts 4 to 30 seconds when its provider is configured, and h3-max-recast accepts 5 to 30 seconds. The docs add that every other catalog model tops out at 15 seconds.

That means a single generated clip can cover an end-screen video only on those models. Read supported_durations from GET /v1/videos/models for the live list, since limits are not uniform.

Assembling 25 seconds from shorter clips

Timeline 1.0 takes one audio spine and ordered video[] slots and returns one MP4. It accepts audio.mode: "silence" with a declared duration_seconds when there is no voiceover, and POST /v1/timeline-1.0/plan is an unbilled preflight that returns duration_seconds without creating a job. Two 13-second slots make a 26-second video, which clears the 25-second line with a second to spare.

curl -X POST https://api.sume.com/v1/timeline-1.0/plan \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "audio": { "mode": "silence", "duration_seconds": 26 },
    "video": [
      { "source_url": "https://media.sume.com/artifacts/artf_demo/a.mp4", "start": 0, "duration": 13 },
      { "source_url": "https://media.sume.com/artifacts/artf_demo/b.mp4", "start": 13, "duration": 13 }
    ]
  }'

Practical notes

Timeline declares that coverage may trail the spine by at most 0.5 seconds, so leave margin above 25 and do not plan a 25.0-second render. Source URLs must already be this workspace's media.sume.com artifacts, so import external files first. A silent video is still valid for an end-screen carrier, but if you want a voiceover, pass audio.url instead.

Check the clip's real length from the job result before you upload.