File Uploads

The File Uploads API provides a presigned-URL workflow for uploading files that can be attached to sandbox sessions as resources. Uploads are limited to 100 MB per file.

To obtain your authentication credentials, install the Release CLI and run release auth login. The CLI stores credentials in ~/.release.yaml.

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Upload Flow

Uploading a file to a sandbox session is a two-step process:

1. Get a presigned URL — POST to the endpoint below with the file metadata. The response contains a presigned_url and an s3_uri.

2. PUT the file content — Send a PUT request to the presigned_url with the raw file bytes as the request body. Set the Content-Type header to the same MIME type you provided in step 1.

Once uploaded, reference the file in a session by using the s3_uri value when creating a session resource of type file (see Session Resources).

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Get Presigned Upload URL

Returns a presigned S3 URL that you can PUT file content to, along with an S3 URI for referencing the uploaded file in session resources.

Endpoint

POST https://backend-{handle}-envs.gcp.release.com/ai/accounts/{accountId}/sandbox_uploads

Authentication

Authenticate using headers from your ~/.release.yaml file. To set this up, install the Release CLI and run release auth login.

Header	Description
X-User-Email	User email from ~/.release.yaml (login field)
X-User-Token	User token from ~/.release.yaml (token field)

Headers

Header	Value
Content-Type	application/json
Accept	application/json

Path Parameters

Name	Type	Required	Description
accountId	string (hashid)	Yes	The Release account ID

Request Body

Field	Type	Required	Description
filename	string	Yes	Name of the file to upload
content_type	string	Yes	MIME type of the file (e.g. text/plain, application/zip)
size_bytes	integer	Yes	File size in bytes (maximum 100 MB)

Example

{
  "filename": "data.txt",
  "content_type": "text/plain",
  "size_bytes": 1024
}

Status Codes

Code	Description
201	Presigned URL generated
401	Unauthorized — invalid or missing credentials
422	Validation error (see error codes below)

Error Codes

Code	Description
file_too_large	File exceeds the 100 MB size limit
no_upload_cluster	No cluster is configured for uploads on this account

Response Body

Field	Type	Description
data.presigned_url	string	URL to PUT the file content to
data.s3_uri	string	S3 URI to reference when creating session resources of type file

Example Responses

201 Created

{
  "data": {
    "presigned_url": "https://s3.amazonaws.com/bucket/path?...",
    "s3_uri": "s3://bucket/path"
  }
}

422 File Too Large

{
  "errors": [
    {
      "code": "file_too_large",
      "message": "File exceeds the 100 MB size limit"
    }
  ]
}

422 No Upload Cluster

{
  "errors": [
    {
      "code": "no_upload_cluster",
      "message": "No cluster configured for uploads"
    }
  ]
}