Seedance 2.5 native 4K: the press claim and what Sume accepts

Seedance 2.5 on Sume tops out at 1080p: the catalog row lists 480p, 720p and 1080p, and a resolution of 4K on seedance-2.5 returns a 400 ("4K is not supported by model seedance-2.5" on the Video Router). The 4K figure comes from press coverage of the June announcement, not from the model's launch post, and Sume does not expose it.

The Next Web, reporting on ByteDance's Beijing conference on June 23, 2026, wrote that Seedance 2.5 produces 30-second clips at native 4K with 10-bit colour (The Next Web, read 2026-10-02). ByteDance Seed's launch post of July 31 describes 30-second generation, references and editing, and states no output resolution (read 2026-10-02). Sume's side is Video Router and the API reference.

What does each source say about resolution?

The two vendor-side sources differ, and Sume follows neither: it exposes what its provider accepts for the model.

What happens if I send 4K anyway?

A 400, before anything is reserved. On POST /v1/videos the catalog check names the value ("seedance-2.5 does not support resolution 4K."). A lowercase 4k is refused on the Video Router with "4k is not supported by Video Router v1." The only 4K generation row in the Video Router docs is gemini-omni-flash-1.1, which lists 360p, 720p, 1080p and 4K; check supported_resolutions for the current list.

How do I get 4K output from a Seedance clip?

Generate at 1080p, then upscale as a second step. Sume has a separate video upscale endpoint for that; How to upscale video to 4K covers scale factors and step order. An upscale of a 1080p render is not the same thing as native 4K generation, and this post does not claim they look alike.

For the first step, the request is the same as any other 1080p job:

curl -X POST https://api.sume.com/v1/videos \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: seedance-1080-001" \
  -d '{"model":"seedance-2.5","prompt":"A slow dolly across a lit bakery counter at dawn","duration":10,"resolution":"1080p"}'

Will Sume add 4K for Seedance 2.5 later?

This post cannot say. The catalog is the source of truth: GET /v1/video-router/models lists resolutions per row, so read it before you build around a limit that may change.