Kling 4.0 · API

Quick start

Three steps: submit a job, poll it, take the video link. Replace YOUR_API_KEY with your key and the commands below run as they are.

Step 1 · Submit (returns a job id at once, HTTP 202)

curl https://nezhagate.com/v1/videos/generations \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "kling-4.0", "prompt": "a dancer spins through falling maple leaves while the camera circles her slowly", "duration": 5, "resolution": "720P", "size": "16:9"}'

Response (HTTP 202)

{
  "id": "img_5c2e8f1a9b3d7e6f0a4c8b2d",
  "object": "video.generation.job",
  "status": "queued",
  "created": 1791281400,
  "model": "kling-4.0"
}

Step 2 · Poll every 5–10 seconds until status is succeeded or failed

curl https://nezhagate.com/v1/videos/jobs/img_5c2e8f1a9b3d7e6f0a4c8b2d \
  -H "Authorization: Bearer YOUR_API_KEY"

Response when it succeeds

{
  "id": "img_5c2e8f1a9b3d7e6f0a4c8b2d",
  "object": "video.generation.job",
  "status": "succeeded",
  "created": 1791281400,
  "model": "kling-4.0",
  "data": [
    {"url": "https://img.nezhagate.com/i/8c1f0e5d2b7a49e3a6d0c4f1b9e2a7d5.mp4"}
  ],
  "usage": {"clips": 1, "model": "kling-4.0"}
}

Step 3 · data[0].url is the clip (MP4). It is kept for 15 days; download it to your own storage to keep it longer.

Complete example (Python: submit, wait, save to disk)

import time
import requests

BASE = "https://nezhagate.com/v1"
HEADERS = {"Authorization": "Bearer YOUR_API_KEY"}

# 1. submit
job = requests.post(f"{BASE}/videos/generations", headers=HEADERS, json={
    "model": "kling-4.0",
    "prompt": "a dancer spins through falling maple leaves while the camera circles her slowly",
    "duration": 5,
    "resolution": "720P",
    "size": "16:9",
}).json()
if "error" in job:
    raise SystemExit(job["error"]["message"])

# 2. poll every 10 seconds, for up to an hour
deadline = time.time() + 3600
while job["status"] not in ("succeeded", "failed") and time.time() < deadline:
    time.sleep(10)
    job = requests.get(f"{BASE}/videos/jobs/{job['id']}", headers=HEADERS).json()

# 3. download the video
if job["status"] == "succeeded":
    url = job["data"][0]["url"]
    with open("kling-4.0.mp4", "wb") as f:
        f.write(requests.get(url).content)
    print("saved", url)
elif job["status"] == "failed":
    print("failed:", job["error"]["code"], job["error"]["message"])
else:
    print("still", job["status"], job["id"])

While queued, the poll also returns queue_position (jobs ahead of yours) and eta_seconds (expected wait). If your time limit passes, do not resubmit: the job is still there, so keep polling the same id later.

Authentication

Authorization: Bearer YOUR_API_KEY
Content-Type: application/json

Create an API Key in the console to start.

At a glance

Request parameters

The JSON body of POST /v1/videos/generations:

Other fields (seed, negative_prompt, fps, watermark and the like) are not passed on and do not change the price; results are always MP4, returned as a url.

Price

Billed per second: cost = the per-second rate of the resolution x (output seconds + the seconds of every reference video). The same reference-video link counts once; reference images and audio are free. The amount is held at submit, settled at the same figure on success and refunded in full on failure. 1 credit = $0.005.

Reference material

• Reference images are references, never a first frame. Say in the prompt what each one is for by its number, e.g. "the character in image 1", "the setting in image 2".
• Reference videos set motion and camera, and combine with reference images. Each 2-30 s and 700-4553 px high (e.g. 1280x720 landscape or 720x1280 portrait; a 480P video fails), 30 s in all. We download and measure each one at submit: a clip whose length cannot be read, one that is too short or not high enough gets a 400 and is not charged.
• Reference audio sets a character's voice and must be 5-30 s of clear human speech; music, sound effects or clips under 5 s are refused. Write the lines to be spoken in the prompt.
• Each image is a public image URL, a data: URI or base64, up to 16 MB; send several as an array in images. We store the images before the job is queued; one that cannot be read is refused with 400, message says which, and nothing is charged.
• Reference files we store are kept for 7 days; results for 15 days.

With reference images, a reference video and reference audio

curl https://nezhagate.com/v1/videos/generations \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "kling-4.0", "prompt": "the character in image 1 swings the spear in the forest of image 2, following the moves in the reference video, and shouts in the voice of the reference audio: come on", "images": ["https://example.com/character.png", "https://example.com/forest.png"], "video_references": ["https://example.com/moves-1280x720.mp4"], "audio_reference": ["https://example.com/voice-8s.mp3"], "duration": 10, "resolution": "720P", "size": "16:9"}'

This job outputs 10 s with a 5 s reference video, so 15 seconds are billed; the reference audio is free.

Job status and fields

GET /v1/videos/jobs/{id} reports these statuses; every field is described in Async jobs. Poll every 5–10 seconds, or let a webhook (below) push the result. Polling is free, and any key of the same account can read the job.

• processing can go back to queued, for example while every line is busy, while a finished clip is fetched again, or after a restart. If a line cannot finish a job, the gateway may hand it to the next line to render again; however many lines it passes through, a job is charged once.
• One account runs up to 50 jobs at a time; further jobs wait in submission order, and a job that has not started after 15 minutes fails and is refunded in full. Job records are kept for 3 days and video links for 15 days.

How long it takes

Our tests (720P / 1080P, 3-5 s) usually rendered in 3-5 minutes; it takes longer when the queue is busy. We wait up to 120 minutes and refund in full on a timeout.

Median render time in our tests: 3.3 min.

Errors and refunds

An error at submit comes back at once as HTTP 4xx / 5xx: no job is created and nothing is charged. A failure after the job was accepted is reported by the job endpoint, and the hold is refunded in full. Every code is listed under Error codes.

Errors at submit

Failed jobs (status failed)

Branch on code, not on the text of message. Treat any code you do not recognise (or a missing one) as upstream_error: resubmitting usually works. Every failed job is refunded in full.

Webhooks instead of polling

Add callback_url when you submit and the moment the job ends, success or failure, the gateway pushes exactly what the poll endpoint returns to that URL, signed and retried on failure. You can also set an account-wide address under Settings → Webhook in the console. Webhook docs →

curl https://nezhagate.com/v1/videos/generations \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "kling-4.0", "prompt": "a dancer spins through falling maple leaves while the camera circles her slowly", "duration": 5, "resolution": "720P", "size": "16:9", "callback_url": "https://your-domain.com/webhook"}'