Update item quantity
POST/helpers/cart/update
Stateless cart helper - Updates the quantity of an item in the cart and returns the updated cart with recalculated totals.
This is a pure function: (existingCart, lineItemId, newQuantity) → newCart
No server-side state - Partners manage their own cart state.
Request
Responses
- 200
- 400
Updated cart with modified quantity and recalculated totals
Invalid request