Inventory shipment webhooks include inventory transfer IDs

We are introducing the inventory_transfer_id to several inventory_shipment webhook payloads to make it easier for developers to identify which inventory_transfer records, if any, a given shipment is related to. This will ease integration burdens and remove the need for developers to merge the datasets on their end to manually build the links.

What changed

Introduces an inventory_transfer_id field to the payloads of the following...

• inventory_shipments/create
• inventory_shipments/delete
• inventory_shipments/add_items
• inventory_shipments/remove_items
• inventory_shipments/update_item_quantities
• inventory_shipments/mark_in_transit
• inventory_shipments/receive_items
• inventory_shipments/update_tracking

Who's affected

This is an additive change, any adopters of the shipment webhooks, upon updating to 2026-10, will get access to this new field.