Kling AI Video Extension
Overview
Extend an existing video by appending additional seconds. The extension endpoint takes the task_id of a completed video and generates a seamless continuation.
Endpoint: POST https://api.klingai.com/v1/videos/video-extend
Request Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
task_id | string | Yes | Task ID of the completed source video |
prompt | string | No | Motion/scene description for extension |
duration | string | No | Extension length: "5" (default) |
mode | string | No | "standard" or "professional" |
model_name | string | No | Default: "kling-v2-master" |
callback_url | string | No | Webhook for completion |
Basic Extension
import jwt, time, os, requests
BASE = "https://api.klingai.com/v1"
def get_headers():
ak, sk = os.environ["KLING_ACCESS_KEY"], os.environ["KLING_SECRET_KEY"]
token = jwt.encode(
{"iss": ak, "exp": int(time.time()) + 1800, "nbf": int(time.time()) - 5},
sk, algorithm="HS256", headers={"alg": "HS256", "typ": "JWT"}
)
return {"Authorization": f"Bearer {token}", "Content-Type": "application/json"}
# Step 1: Generate the initial 5s video
initial = requests.post(f"{BASE}/videos/text2video", headers=get_headers(), json={
"model_name": "kling-v2-master",
"prompt": "A rocket launching from a desert landscape, cinematic",
"duration": "5",
"mode": "standard",
}).json()
initial_task_id = initial["data"]["task_id"]
# Wait for completion...
# (poll until task_status == "succeed")
# Step 2: Extend by 5 more seconds
extension = requests.post(f"{BASE}/videos/video-extend", headers=get_headers(), json={
"task_id": initial_task_id,
"prompt": "The rocket ascends through clouds into the stratosphere",
"duration": "5",
"mode": "standard",
}).json()
ext_task_id = extension["data"]["task_id"]
# Step 3: Poll extension task
while True:
time.sleep(15)
result = requests.get(
f"{BASE}/videos/video-extend/{ext_task_id}", headers=get_headers()
).json()
if result["data"]["task_status"] == "succeed":
extended_url = result["data"]["task_result"]["videos"][0]["url"]
print(f"Extended video: {extended_url}")
break
elif result["data"]["task_status"] == "failed":
print(f"Failed: {result['data']['task_status_msg']}")
break
Chain Multiple Extensions
def chain_extensions(initial_task_id: str, prompts: list[str],
duration: str = "5", mode: str = "standard") -> list[str]:
"""Chain multiple extensions to build a longer video."""
current_task_id = initial_task_id
video_urls = []
for i, prompt in enumerate(prompts):
print(f"Extension {i + 1}/{len(prompts)}: submitting...")
# Submit extension
r = requests.post(f"{BASE}/videos/video-extend", headers=get_headers(), json={
"task_id": current_task_id,
"prompt": prompt,
"duration": duration,
"mode": mode,
}).json()
ext_task_id = r["data"]["task_id"]
# Poll for completion
while True:
time.sleep(15)
result = requests.get(
f"{BASE}/videos/video-extend/{ext_task_id}", headers=get_headers()
).json()
status = result["data"]["task_status"]
if status == "succeed":
url = result["data"]["task_result"]["videos"][0]["url"]
video_urls.append(url)
current_task_id = ext_task_id # next extension chains from this
print(f"Extension {i + 1} complete: {url}")
break
elif status == "failed":
raise RuntimeError(f"Extension {i + 1} failed: {result['data']['task_status_msg']}")
return video_urls
Usage: Build a 20-Second Video
# Generate initial 5s
initial_r = requests.post(f"{BASE}/videos/text2video", headers=get_headers(), json={
"model_name": "kling-v2-master",
"prompt": "Morning sunrise over a mountain lake, mist rising",
"duration": "5",
"mode": "standard",
}).json()
initial_id = initial_r["data"]["task_id"]
# ... poll until complete ...
# Chain 3 more extensions = 5 + 5 + 5 + 5 = 20 seconds total
extensions = chain_extensions(initial_id, [
"Sun rises higher, birds begin flying across the lake",
"A deer approaches the water's edge to drink",
"Wide shot pulling back to reveal the full mountain range",
])
Cost
Each extension costs the same as a new generation:
| Extension Duration | Standard | Professional |
|---|---|---|
| 5 seconds | 10 credits | 35 credits |
A 20-second video (initial + 3 extensions) costs 40 credits in standard mode.
Error Handling
| Error | Cause | Fix |
|---|---|---|
Invalid task_id | Source task doesn't exist | Verify task_id is from a completed generation |
| Source not complete | Extending a task still processing | Wait for source task to reach succeed status |
| Extension failed | Prompt conflict with source | Align extension prompt with original scene |
Prerequisites
- A completed, rights-cleared or synthetic source draft, approved extension brief, authorized workspace and credit budget, policy review, draft-only destination, and a rollback/removal owner.
Instructions
- Confirm source ownership, completion state, and approved continuity brief before creating an extension; do not use private, unlicensed, or policy-restricted material.
- Submit one watermarked draft canary within the approved duration and credit cap, then verify policy, rights, quality, and destination controls.
- Halt on continuity, policy, rights, or budget drift and delete the extension task instead of publishing it.
- Promote only after owner approval; retain a redacted receipt and remove temporary assets at the agreed retention boundary.
Output
Produce an extension receipt with source task reference, rights classification, mode/duration, credit estimate, policy review, draft destination, approver, retention/removal reference, and task ID. Exclude prompts, identities, and asset URLs.
Examples
source=synthetic-task-42; rights=cleared; duration=5s; mode=standard; policy=pass; destination=draft-only; cleanup=24h is safe for review.