Kling 4.0 vs Seedance 2.5: both reach 30 s, one runs on Sume

Kling 4.0 and Seedance 2.5 both advertise clips up to 30 seconds, so length does not separate them. The practical difference for a Sume user is access: seedance-2.5 is a catalog id you can call on Sume today (4 to 30 seconds at 480p, 720p or 1080p), while Kling 4.0 is not an id you can call on Sume today. If you need a 30-second clip through one API, Seedance 2.5 or wan-3.0 is the route; Kling 4.0 has to be used where Kling offers it.

The rest of this page lays the two vendor pages next to the Sume catalog so you can decide on facts rather than launch posts. The vendor numbers below are only what each vendor's own page states on 2026-10-03; where a page is silent, the table says so rather than guessing.

What each vendor page states

Kling's Kling 4.0 vs 3.0 page lists native generation of 3 to 30 seconds, 720p, 1080p and 4K output, a 21:9 ultrawide option, two-channel stereo audio with improved lip-sync, 10-bit HDR at 1080p and 4K, up to 10 keyframes, and up to 15 combined reference assets. It also lists multi-shot storytelling and native audio with dialogue.

ByteDance Seed's Seedance 2.5 page is lighter on numbers. It says you can create videos up to 30 seconds in a single generation, with the option to extend twice, and it describes white-model control and green-screen editing. It does not state resolutions, reference counts or audio parameters, so this post does not either.

What Sume offers instead

Sume's Video Router catalog lists seedance-2.5 at 4 to 30 seconds and 480p, 720p or 1080p, and wan-3.0 at 2 to 30 seconds. Both can sit behind the same request shape on POST /v1/video-router/generate, or on the OpenRouter-compatible POST /v1/videos described in Video generation. Audio and video references are honored by the Seedance 2.x models and Wan 3.0.

Two details change the comparison. First, Sume does not expose Seedance's extend-twice workflow as a documented feature; on Sume you ask for the full length in one request, up to 30 seconds on seedance-2.5. Second, the Kling 4.0 resolution and HDR claims have no Sume counterpart, because there is no Kling 4.0 id in the catalog. Sume bills provider list price times 1.25 on every Video Router model, so budget from the provider list price for the model you pick, not from the Kling page.

A request that matches the Seedance side

This asks for a 30-second vertical clip at 720p. The limits are per model, so read capabilities from GET /v1/video-router/models if you change the id.

``bash curl -X POST https://api.sume.com/v1/video-router/generate \ -H "Authorization: Bearer $SUME_API_KEY" \ -H "Content-Type: application/json" \ -H "Idempotency-Key: seedance-30s-001" \ -d '{ "model": "seedance-2.5", "prompt": "A vertical product demo on a desk, natural light, slow push-in", "resolution": "720p", "duration": 30, "aspect_ratio": "9:16", "mode": "async" }' ``

How to choose

Pick Kling 4.0 on Kling's own product if the features that only its page lists (4K, 10-bit HDR, 10 keyframes, 15 combined references) decide the job. Pick seedance-2.5 on Sume if you need a 30-second clip from an API with idempotency keys, async jobs and a single bill. If cost matters more than the model name, wan-3.0 also reaches 30 seconds on Sume; the earlier video model chooser and the post on extending twice versus one 30-second generation cover the trade-offs in more depth.