> Deprecated: > Product subscription app extensions won't be supported as of December 3, 2025. You should migrate existing product subscription app extensions to [purchase options extensions](/docs/apps/build/purchase-options/purchase-options-extensions). Get a fresh session token for communication with your app's backend service. Calls to Shopify APIs must be made by your app’s backend service.
() => Promise<string | UndefinedType>
| Get a fresh session token. |