Kling 4.0 UGC

Endpoint

POST https://api.roasos.com/v1/ugc/kling-4

Send your API key as a bearer token. The key needs the scope api:write. Every paid request also needs an Idempotency-Key header.

The envelope fields quote_only, quote_id, webhook_url and wait_timeout_seconds behave the same on each model endpoint. Refer to Jobs and Quotes and credits.

Good at

A spoken ad from a scene that already shows the person and the set. In reference mode (no scene), name a saved person, a saved product or reference images, and the model makes the ad in one generation. The saved person is sent as an identity element.

Kling 4.0 is the only Kling UGC model since 2026-10-29. It replaced the Kling 3 and Kling O3 UGC endpoints, and those endpoints are removed.

Pricing

The unit is one clip. Pricing key: kling-4.

The credits come from the roasOS pricing table. No other field changes the price. To get the exact price of your request, send it with quote_only: true first.

Modes

• standard
• reference

roasOS selects the mode from the media fields of your request. You do not send a mode.

Provider endpoints: kling/v4/image-to-video · kling/v4/reference-to-video.

Request fields

The schema is strict. A field that is not in this table gets 400 unsupported_option. The field names are the roasOS role names. One role has one name in every family.

Media

This endpoint accepts these media roles:

• avatar_id — identity; the saved character reference sheet, with a derived portrait only where the model requires a single face or source frame
• product_id — product; resolves to the product image list
• references — style and appearance references
• scene_id — first frame — a scene this workspace owns
• scene_image — first frame — a CDN image

Every other role is refused: elements, product_images, reference_images, image_url, end_image_url, video_urls, video_url, audio_urls, audio_url, voice_id. A refused role gets 400 unsupported_option.

Prompt

• Standard mode: the platform adds a short facts block to the script. If the script and the block are more than 2,500 characters, the platform removes the block.
• Reference mode: do not write @Image tags. The platform adds them.
• Write the words to be spoken in quotes, with the delivery: says with warm energy: "…".
• Write motion as physics: "she lifts the jar to chest height".
• Keep the camera static for a talking head. Use one subject and one action.
• Lip-sync is best for about five seconds of continuous speech. Split a long script into shots or clips.

Not exposed

These catalog entries describe omitted inputs, pinned values and source constraints. They do not imply that the provider accepts every listed field.

• video_urls — these values are not available: MOV containers.
• middle_image_urls — not accepted by this public endpoint.
• voice_ids — not accepted by this public endpoint.
• mode — pinned to image-to-video.

Result

The result kind is ugc. Always present: url.

{
  "data": {
    "id": "gen_…",
    "kind": "ugc",
    "model": "kling-4",
    "status": "completed",
    "result": {
      "url": "https://cdn.roasos.com/workspaces/ws_01/result"
    }
  }
}

The files are immutable objects on https://cdn.roasos.com. A result URL is a valid media input for your next request.

Example

The three steps are always the same: quote, run, poll.

# 1. Quote. Nothing is spent.
curl -X POST https://api.roasos.com/v1/ugc/kling-4 \
  -H "Authorization: Bearer roasos_sk_live_..." \
  -H "Idempotency-Key: 0f1c9e2a-kling-4-0001" \
  -H "Content-Type: application/json" \
  -d '{"quote_only":true,"script":"Two drops, morning and night. That is the whole routine."}'
# 200 { "data": { "kind": "quote", "quote_id": "q_7Hk...", "credits": 9, "expires_at": "...",
#        "confirmation": { "model": "kling-4", "example": "3s_1080p" } } }

# 2. Run. Same body, same Idempotency-Key, quote_id in place of quote_only.
curl -X POST https://api.roasos.com/v1/ugc/kling-4 \
  -H "Authorization: Bearer roasos_sk_live_..." \
  -H "Idempotency-Key: 0f1c9e2a-kling-4-0001" \
  -H "Content-Type: application/json" \
  -d '{"quote_id":"q_7Hk...","script":"Two drops, morning and night. That is the whole routine."}'
# 201 { "data": { "id": "gen_...", "status": "queued", "credits_reserved": 9 } }

# 3. Poll, then read the result.
curl https://api.roasos.com/v1/jobs/gen_.../status -H "Authorization: Bearer roasos_sk_live_..."
curl https://api.roasos.com/v1/jobs/gen_.../result -H "Authorization: Bearer roasos_sk_live_..."

See also

• llms.txt for this model — the same facts as one plain-text file for an agent.
• GET https://api.roasos.com/v1/catalog/kling-4 — the machine-readable form: enums, defaults, limits and prices. Refer to the API reference.
• Jobs — how to poll a job and read its result.
• Provider endpoints: kling/v4/image-to-video · kling/v4/reference-to-video.