Kling 3 on Sume: a 720p request renders 1080p at the same rate

On Sume, Kling Video v3 Pro renders every clip at 1080p, and a request that asks for 720p is accepted and still renders 1080p. The billed rate depends on whether audio is on, not on the resolution: $0.14 per second without audio and $0.21 with audio, which is the list rates of $0.112 and $0.168 times 1.25.

That is a surprise for callers coming from rows where 720p is cheaper than 1080p, such as Wan 3.0 ($0.125 billed at 720p, $0.25 at 1080p).

Why the alias exists

The catalog comment explains it: the upstream queue for Kling v3 Pro has no resolution input, and a 720p request came back as 1920x1080. The catalog therefore lists 1080p only, and keeps a quiet alias that maps 720p to 1080p so older callers, such as the Videos picker and Agents, do not break. The alias is not part of the public row, which is why supported_resolutions shows only 1080p.

What else the row limits

The same row takes 4 to 15 seconds, 16:9, 9:16 or 1:1, text-to-video or start and end frames, and has no reference inputs. A request with reference_image_urls fails with a message that the model supports text-to-video or start/end frames only.

What this means for a draft pass

Do not use Kling for cheap low-resolution drafts: there is no lower tier to drop to. A 10-second draft on Kling costs the same $1.40 as the final. If you want a draft that is cheaper, choose a row that lists 480p: Wan 3.0 ($0.0625 per second) or one of the Seedance rows.

• Final at 1080p on Kling, audio on: 10 s = $2.10.
• Draft on Wan 3.0 at 480p: 10 s = $0.625.
• Do not read the alias as a 720p price tier. There is none.

Checking before you submit

Read the row from GET /v1/videos/models and confirm supported_resolutions. Send 1080p explicitly so that your own logs match what rendered.