Upload a file to xAI's storage. Returns the file's metadata. Files can be referenced by ID anywhere a `file_id` is accepted (e.g. chat attachments). Maximum file size: 50 MB. Files are kept until you delete them, or until `expires_after` elapses if set at upload time.

Request Body

expires_after (integer | null) — Optional TTL in seconds (measured from upload time). Must be between 3600 (1 hour) and 2592000 (30 days). If unset the file does not expire.
Accepts either a plain integer or the OpenAI SDK deepObject form (`expires_after[anchor]=created_at` + `expires_after[seconds]=N`) as separate multipart fields. The anchor+seconds form must arrive before the `file` part.
file (string, required) — The file to upload. The filename from the multipart `Content-Disposition: filename=` header is recorded as the file's `filename`.
purpose (string | null) — Optional purpose label, accepted for OpenAI SDK compatibility. xAI does not enforce or interpret this field. Setting `"assistants"` is the conventional choice.

Response Body

bytes (integer, required) — The size of the file, in bytes.
created_at (integer, required) — The Unix timestamp (in seconds) for file creation time.
expires_at (integer | null) — The Unix timestamp (in seconds) for file expiry time. null if file does not expire.
filename (string, required) — The name of the file.
id (string, required) — The file identifier, which can be used in other API requests.
object (string, required) — The object type, which is always `file`. Only included for compatability.
public_url (string | null) — Public URL for the file. Only present when the file has an active public URL.
public_url_expires_at (integer | null) — Unix timestamp (seconds) when the public URL expires. Only present when the public URL has an independent expiry.
purpose (string) — The intended purpose of the uploaded file. Only included for OAI compatability.

**Response example:**

{
  "id": "file_a128090d-f0c9-4873-bd84-e499777e7417",
  "object": "file",
  "bytes": 12345,
  "created_at": 1762345678,
  "expires_at": 1762432078,
  "filename": "document.pdf",
  "purpose": ""
}

POST /v1/files:initialize

API endpoint for POST requests to /v1/files:initialize.

Method: POST
Path: /v1/files:initialize

POST /v1/files:uploadChunks

API endpoint for POST requests to /v1/files:uploadChunks.

Method: POST
Path: /v1/files:uploadChunks