Everyone has the jar. Third one along, mostly full, bought because the recipe said cumin and the cupboard was too far away to check. Buying it again is not a failure of memory. It is what happens when the list and the cupboard are two separate things.
The list should read the cupboard
A shopping list that knows what is at home can do something a paper list cannot: leave things off. Add a recipe, and only the missing ingredients reach the list. The rest are already on a shelf.
Order by aisle, not by recipe
A list grouped by recipe sends you back and forth across the shop. A list grouped by aisle walks you through it once. It is a small change that saves a surprising amount of time, and it is the sort of thing software should do without being asked.
One list, everyone in the house
The other half of the problem is that lists live on one person's phone. A shared list, updated as things get picked up, avoids the two-loaves problem — and means whoever is nearest the shop can go.
Grocerr AI does all three: it checks the pantry before adding, groups by aisle, and shares across the household.