Black Friday supercut in Timeline: 12 segments vs auto chunking

A Black Friday supercut of more than 12 clips needs the auto render strategy in Sume Timeline 1.0. With strategy set to single, a request above 12 segments is refused with render_strategy_unsafe; with auto, Sume chunks the render. The request can hold 1 to 200 video slots.

Limits

From the Timeline docs, as of 2026-10-08.

A 40-clip example

Forty 3-second product clips make 120 seconds, which is 2 output minutes and $0.20 to join. Auto splits the render into chunks, so no render holds more than 12 segments. Use hard cuts for most joins; adjacent fades past 8 are refused with too_many_chained_transitions.

• Plan first, render second.
• Keep each segment's source resolution consistent so the fit setting does not surprise you.
• Music: one audio track up to 1800 seconds, or up to 20 parts.

Cost check

Cost depends on output minutes only: 40 x 3 s = 120 s = 2 minutes = $0.20, whatever the number of chunks. Clip generation is the larger line: a 3 s Wan 3.0 clip at 720p is 3 x $0.125 = $0.375, so 40 of them are $15.00.

Soundtrack and captions

A supercut usually has one music bed. Timeline accepts audio of 1 to 1800 seconds, and the soundtrack can duck under voice by 0 to 20 dB (duck_db). If you want captions on top, burn them after the join: the caption job is $0.20 for a clip up to 60 seconds.

For a 120-second cut, captions need two jobs, because 60 seconds is the cap per job: 2 x $0.20 = $0.40.

• Join: $0.20 for 120 s.
• Captions: 2 x $0.20 = $0.40.
• Total post-production: $0.60.

Before you scale

The plan endpoint is the right place to learn about limits. It is not billed, and it reports problems such as too many chained transitions or a segment count that the single strategy would refuse. Make it a step of the script: plan, check for errors and warnings, and only then render. For a catalog of supercuts, plan every one before you render any.