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kling/4.0/reference-to-video

Kling 4.0 reference-to-video casts a 3-30 second clip from up to 10 images, 5 videos and 3 voice clips that you name in the prompt as @Image1, @Video1 and @Audio1. Output is 720p or 1080p with a stereo soundtrack.

From $0.216/s
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Quickstart

Examples use the selected endpoint’s public parameter definitions. Replace the API key and example media, then send the request from your server.

SDKs & integrations
POSThttps://api.spicyapi.ai/api/v1/jobs/createTask

API authentication

Keep the API key in the server environment variable SPICY_API_KEY. Use Bearer authentication and Content-Type: application/json for JSON requests.

Authorization: Bearer $SPICY_API_KEY
Sample outputUse this example
# Generate the idempotency key once; reuse it when retrying after a lost response.
export SPICY_IDEMPOTENCY_KEY="${SPICY_IDEMPOTENCY_KEY:-$(uuidgen)}"
curl -X POST https://api.spicyapi.ai/api/v1/jobs/createTask \
  -H "Authorization: Bearer $SPICY_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $SPICY_IDEMPOTENCY_KEY" \
  -d '{
  "model": "kling/4.0/reference-to-video",
  "input": {
    "aspect_ratio": "auto",
    "duration_seconds": 5,
    "prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
    "resolution": "720p"
  }
}'

# Copy data.taskId from the response into TASK_ID, then poll the status.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.spicyapi.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
  -H "Authorization: Bearer $SPICY_API_KEY"

Generated from this model’s input schema — the same one the API validates every request against.

Input parameters

Place these fields inside the request body’s input object. Names and types match the API. Do not assume a default when none is specified.

promptstringRequired

Say what each reference is and what the shot does with it. Write @Image1, @Image2 for images, @Video1 for videos and @Audio1 for audio clips, each numbered in upload order.

Default
Not specified
Constraints
minLength:1
duration_secondsintegerOptionalAffects price

Whole seconds, 3 to 30 (default 5). Drives the price.

Default
5
Constraints
minimum:3
maximum:30
keep_original_audiobooleanOptional

Off by default. On keeps the reference video's own sound instead of generating a new soundtrack; it only matters when you give a reference video.

Default
false
resolutionstringOptionalAffects price

720p or 1080p (default 720p). 1080p costs more per second.

Default
"720p"
Allowed values
"720p""1080p"
aspect_ratiostringOptional

auto (default) follows the reference images or video; 16:9, 9:16, 1:1 or 21:9 set it yourself. It does not change the price.

Default
"auto"
Allowed values
"auto""16:9""9:16""1:1""21:9"
reference_audio_urlsarray<string>Optional

Up to 3 audio clips of 5 to 30 seconds each for a voice or a sound, referred to as @Audio1, @Audio2. Write the spoken words in the prompt. They do not change the price.

Default
Not specified
Constraints
minItems:1
maxItems:3
reference_video_urlsarray<string>OptionalAffects price

Up to 5 videos, 30 seconds in total, for motion, camera and pacing, referred to as @Video1, @Video2. Their seconds, each clip rounded up to a whole second, are billed at a lower rate than output seconds.

Default
Not specified
Constraints
minItems:1
maxItems:5
reference_image_urlsarray<string>Optional

Up to 10 images of people, objects, outfits or places, referred to as @Image1, @Image2 and so on. They do not change the price.

Default
Not specified
Constraints
minItems:1
maxItems:10

Track the task

HTTP 202 means the task was accepted, not completed. Save the returned taskId and query that task. Do not create another task while waiting for its result.

Accepted response
HTTP/1.1 202 Accepted
Location: /api/v1/jobs/recordInfo?taskId=job_01k3m8x9q2z4v7n5p6r8s0t1w3

{
  "code": 200,
  "msg": "success",
  "request_id": "req_example_create",
  "data": {
    "taskId": "job_01k3m8x9q2z4v7n5p6r8s0t1w3",
    "state": "queued",
    "estimatedCost": "0.750000"
  }
}

The accepted response includes the estimate so your app can show the same amount in task history and billing.

Read the job
curl --get "https://api.spicyapi.ai/api/v1/jobs/recordInfo" \
  --data-urlencode "taskId=$TASK_ID" \
  -H "Authorization: Bearer $SPICY_API_KEY"

Start polling at about 2 seconds and gradually increase the interval. Stop at a terminal state. After a connection failure, query the original taskId. Retry creation only with the original idempotency key and body.

Or let the callback find you
import { verifyWebhook } from "@spicyapi/sdk";

// express.raw keeps the bytes we signed; express.json never matches.
app.post("/hooks/spicy", express.raw({ type: "application/json" }), (req, res) => {
  const { payload } = verifyWebhook({
    rawBody: req.body,
    timestamp: req.header("X-Webhook-Timestamp"),
    signature: req.header("X-Webhook-Signature"),
    payloadVersion: Number(req.header("X-Webhook-Payload-Version")),
    secret: process.env.SPICY_WEBHOOK_SECRET,
  });
  res.status(200).end();
  void handleFinishedTask(payload);
});

Pass callBackUrl when you create the task and the finished record is POSTed to you — no polling loop at all. Every delivery carries X-Webhook-Timestamp, X-Webhook-Signature and X-Webhook-Payload-Version. The signature is a base64 HMAC-SHA256 over taskId.timestamp.sha256(body), so it must be checked against the raw bytes: parsing the JSON and re-serialising it changes them and the check will fail. Failed deliveries are retried, so the same taskId can arrive twice — make the handler idempotent. Answer 2xx first and do the work afterwards; a slow handler is treated as a failed delivery.

Read the result

Consume output only when state is succeeded. On failure, use errorCode, errorMessage and request_id to investigate. Example costs and states do not represent an actual bill.

Completed response example
{
  "code": 200,
  "msg": "success",
  "request_id": "req_example_record",
  "data": {
    "taskId": "job_01k3m8x9q2z4v7n5p6r8s0t1w3",
    "model": "kling/4.0/reference-to-video",
    "state": "succeeded",
    "output": {
      "assets": [
        {
          "key": "tasks/2026/08/28/job_01k3m8x9q2z4v7n5p6r8s0t1w3/3f7a1c9e5b2d48f0a6c1e3d5b7f9a1c3.mp4",
          "mime": "video/mp4",
          "url": "https://example.r2.cloudflarestorage.com/results/job_01k3m8x9q2z4v7n5p6r8s0t1w3/result.mp4?X-Amz-Signature=SIGNATURE_FROM_RESPONSE",
          "expiresAt": "2026-08-28T12:20:08.000Z"
        }
      ]
    },
    "cost": "0.750000",
    "settled": true,
    "createdAt": "2026-08-28T12:00:00Z",
    "completedAt": "2026-08-28T12:00:30Z"
  }
}

For each available asset, open or download assets[].url directly without an API Authorization header. The signed URL expires at expiresAt; poll the task again to refresh it while the asset remains within its retention period. A pending or unavailable asset has no URL. Treat signed URLs as private.

SDKs & integrations

Use SpicyAPI in your app, terminal, AI assistant or visual workflow. Choose a setup guide below.

SDKs
TypeScript · Python · Go · PHP · Java
CLI
Terminal commands and automation scripts.
MCP
Claude Code · Cursor · Codex
Agent Skill
Reusable instructions for your AI assistant.
n8n
Self-hosted community nodes and importable HTTP Request templates for n8n Cloud.
ComfyUI
Image, video and audio workflows on a node canvas.

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Browse ready-to-use workflows

Use it in ComfyUI

Install the SpicyAPI nodes from ComfyUI Manager or with the command below, then search for Kling 4.0 · Reference to Video on the canvas. The node has the same options as this page and shows its price before it runs.

cd ComfyUI/custom_nodes
git clone https://github.com/spicyapi-ai/comfyui-spicyapi
Workflow examplesSetup guideSource on GitHub