OneBox: Stop Split Shipping

Stock in more than one location? Shopify can split an order into two shipments: two labels for you, and your customer may even see two shipping fees stacked into one price. OneBox registers a fulfillment constraint that runs inside Shopify's own checkout, before rates are calculated. Whenever a single location can fulfill the entire order, checkout produces one shipment. When none can, you choose: let it split with a clear buyer notice, or block checkout for never-split product lines.