LTX-2.5 Fast 20 s vs Pro 10 s: long takes on Sume

LTX-2.5 Fast generates up to 20 seconds at 720p or 1080p, while LTX-2.5 Pro covers 6 to 10 seconds at 1080p. Sume does not list an LTX model id, but two catalog ids take longer single clips: wan-3.0 accepts 2 to 30 seconds and seedance-2.5 accepts 4 to 30 seconds at 480p, 720p or 1080p.

LTX-2.5 limits as reported

The LTX launch coverage lists two model ids, ltx-2.5-fast and ltx-2.5-pro, released Aug 11, 2026. Fast reaches up to 4K, with 20 seconds at 720p and 1080p and 10 seconds at 4K. Pro is 1080p only, at 6 to 10 seconds.

What Sume lists for 20 seconds and longer

Sume's docs say limits are per model and every other catalog model tops out at 15 seconds. The two long-take ids are the exceptions that matter here. wan-3.0 also honors audio and video references, and seedance-2.5 is the id used in the docs' own Video Router example.

Choosing between them

A single long take avoids the seams that stitched clips can show, such as a changed face or shifted lighting at each cut. A longer clip also costs more per request and takes longer to render, so test the idea at a short duration first.

• Need exactly 4K: LTX-2.5 Fast is the one reported to reach it; Sume lists no equivalent
• Need 20 to 30 seconds in one request on Sume: seedance-2.5 or wan-3.0
• Need a clip under 10 seconds: any catalog id works, so pick on look and price

Read the limits before you submit

Read capabilities from the catalog instead of hard-coding limits, since each model advertises its own envelope:

curl https://api.sume.com/v1/video-router/models \
  -H "Authorization: Bearer $SUME_API_KEY"