Recap reel of 12 deal clips: 12 slots is the last single pass

A recap of 12 deal clips fits in one Sume timeline render with exactly one slot per clip. The default render.strategy of auto chunks a render once it passes 12 segments, and single is refused above 12 slots with render_strategy_unsafe. So 12 slots is the last count that renders in a single pass, and a 13th slot makes auto chunk the job.

These limits come from Timeline 1.0 (read 2026-10-06). A timeline holds 1 to 200 video slots, an audio spine of 1 to 1800 seconds, and bills $0.10 per output minute, rounded up.

How long can the recap be?

The output length is the audio spine's audio.duration_seconds. Twelve 5-second deal clips make a 60-second recap, which is one billable minute, and each extra second past 60 starts a second minute.

What should the request contain?

Each slot needs source_url, a start on the spine, and a duration. video[0].start must be 0, later starts must increase, and a transition is allowed only after the first slot.

• Use fit: "cover", the default, for clips already shot in 9:16.
• Keep fades short: a transition is at most 1 second and at most half of the shorter neighbor.
• More than 8 adjacent fades is refused with too_many_chained_transitions, so make some of the 12 joins hard cuts.
• Leave render.strategy at auto, and let Sume chunk when you add a thirteenth clip.

Should I send plan first?

Yes. POST /v1/timeline-1.0/plan compiles the document without creating a job or reserving credits, and returns duration_seconds, segment_count, billable_minutes, and estimated_cost_usd_micros. A plan cannot predict padding or looping warnings for short sources.