Kling 3.0 allows 3 seconds at Kling; Sume's kling-3 starts at 4

If you plan a Short around Kling 3.0 and want a 3-second beat, the two ranges differ. Kling's own model guide lists a flexible duration of 3 to 15 seconds, read on 2026-10-04. Sume's kling-3 row in the Video Router catalog lists duration_seconds from 4 to 15, so a 3-second request does not match the catalog row.

The catalog is the contract, not the vendor page. Sume exposes it at GET /v1/videos/models, and a request is checked against the supported_durations of the model you name, per the video generation docs. The practical answer is to ask for 4 seconds and cut the extra second.

The 4-second clip and a trim

Submit kling-3 with duration: 4, then cut the range you want with Video trim. Trim takes a video_url on media.sume.com, a start, and exactly one of end or duration, and it returns a new MP4. Import the finished clip first, because the API does not fetch from the open internet.

import os
import requests

headers = {
    "Authorization": f"Bearer {os.environ['SUME_API_KEY']}",
    "Idempotency-Key": "kling-beat-001",
}
body = {
    "model": "kling-3",
    "prompt": "A hand sets a ceramic mug on a wooden desk, morning light",
    "duration": 4,
    "resolution": "1080p",
    "aspect_ratio": "9:16",
    "generate_audio": False,
}
resp = requests.post("https://api.sume.com/v1/videos", headers=headers, json=body)
print(resp.status_code, resp.json().get("id"))

What the extra second costs

The registry lists Kling v3 Pro at $0.112 per second with audio off and $0.168 with audio on, and Sume reserves provider list times 1.25. That is $0.14 and $0.21 per second, so a 4-second silent clip is $0.56 and the 3-second version you keep still costs $0.56, because you pay for the generated seconds. The trim is a separate job, so budget it too. If one second of waste matters across hundreds of beats, the cheaper route is a model whose floor is lower: wan-3.0 accepts 2 to 30 seconds.

Quick comparison

Use the Kling page to decide whether the model suits the shot, and the Sume catalog to decide what you can send.