---
title: "Extend a video by generating continuation content.
This is an asynchronous operation that returns a request_id for polling."
method: POST
path: "/v1/videos/extensions"
tags: ["v1"]
---

# Extend a video by generating continuation content.
This is an asynchronous operation that returns a request_id for polling.

`POST /v1/videos/extensions`

## Request body

- ExtendVideoRequest — Request for extending a video for `/v1/videos/extensions` endpoint
  - `duration` integer, nullable — Duration of the extension segment to generate in seconds (2-10). Defaults to 6 seconds if not specified.
  - `model` string, nullable — Model to be used.
  - `output` VideoOutput — Output destination for generated video.
    - `upload_url` string, required — Signed URL to upload the generated video via HTTP PUT.
  - `prompt` string, required — Prompt describing what should happen next in the video.
  - `storage_options` StorageOptions — Configuration for storing generation output in the Files API. When provided in a generation request, the output is stored as a permanent file and a `file_output` reference is included in the response.
    - `expires_after` integer, nullable — Seconds from now until the file auto-expires. Maximum 2592000 (30 days). If omitted, the file does not expire.
    - `filename` string, required — Filename for the stored file.
    - `public_url` union — Accepts either `true` (create public URL with defaults) or a configuration object with explicit options. **Variant order matters for `#[serde(untagged)]`:** `Flag` must come before `Options` so that JSON `true`/`false` match `Flag` rather than falling through to the object variant. **Serialization note:** Proto→REST readback always constructs `Options(...)`, never `Flag`, so responses always emit the object form. `Flag` only appears on the deserialization (request) path.
      - boolean — `true` = create public URL with default options (no independent expiry). `false` = no public URL (equivalent to omitting the field).
      - PublicUrlOptions — Configuration for creating a public URL alongside file storage.
        - `expires_after` integer, nullable — Seconds from now until the public URL expires. Must be between 3600 (1 hour) and 2592000 (30 days). If omitted and the file has a TTL (`expires_after` on the file), the public URL inherits the file's expiry. If omitted and the file has no TTL, the public URL remains valid indefinitely until the file is deleted or the URL is explicitly revoked via `POST /v1/files/{file_id}/public-url/revoke`.
  - `video` VideoUrl, required — Video input for editing and extension requests. Accepts a public URL, a base64-encoded data URL, or a file_id from the xAI Files API.
    - `file_id` string, nullable — File ID from the xAI Files API. Mutually exclusive with `url`. The file must be a video (e.g., MP4) and fully uploaded.
    - `url` string — URL of the video (public URL or base64-encoded data URL). The video must have the `.mp4` file extension and be encoded with `.mp4` supported codecs such as H.265, H.264, AV1, etc. Required when `file_id` is not set.

## Response `200`

Video extension started successfully

- StartDeferredResponse — Response for starting a deferred operation.
  - `request_id` string, required — A unique request ID to poll for the result.

## Other responses

- `400` — Bad request. The request is invalid or an invalid API key is provided.
- `422` — Unprocessable Entity. There are missing fields in the request body.

---

[API](https://skmtc.net/x/apis/xai-s-rest-api.md) · [All operations](https://skmtc.net/x/apis/xai-s-rest-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/x/xai-s-rest-api/versions/8f6014272113/schema)