One basket, four kinds of offer.
Letting a full-menu dish, a happy hour item and a surplus bag share a checkout was harder than it sounds and non-negotiable.
Each offer type has different rules. Surplus is pickup-bound and quantity-limited. Happy hours expire. Full menu is always available. The tidy engineering answer is to keep them apart.
The tidy answer is also a worse product. People do not shop by mechanic; they assemble a dinner. Forcing two checkouts to combine a discounted main with a surplus dessert is a tax on exactly the behaviour we want.
If the marketplace understands four kinds of value, the basket has to as well.
So the basket resolves the constraints instead of the customer: it picks the fulfilment both items can honour, warns when a window is tightening, and shows one total with the saving stated plainly.
