InventoryTransferSetItemsUserError

This mutation sets the quantity for one or more line items on a Transfer.

Only the items you include in the lineItems field are updated. Items already on the transfer but not referenced in your update will stay unchanged. Each inventory item may appear at most once in lineItems; duplicate inventoryItemId entries are rejected.

For each entry in lineItems:

• If the inventory item isn't yet on the transfer, a new line item is added with the provided quantity.
• If the inventory item is already on the transfer, the provided quantity replaces the line item's processableQuantity. Any quantity outside the processable portion (for example, already shipped or picked for shipment) is preserved, so the resulting total quantity equals the preserved portion plus the provided quantity.

Passing a quantity of 0 is only allowed for transfers in DRAFT status; on READY_TO_SHIP or IN_PROGRESS transfers it returns an INVALID_QUANTITY error. On DRAFT transfers, quantity: 0 leaves a zero-quantity line item on the transfer; it does not remove the item. To remove a line item from a transfer, use inventoryTransferRemoveItems.

Caution: As of 2026-01, this mutation supports an optional idempotency key using the <code>@idempotent</code> directive. As of 2026-04, the idempotency key is required and must be provided using the <code>@idempotent</code> directive. For more information, see the <a href="https://shopify.dev/docs/api/usage/idempotent-requests">idempotency documentation</a>.