Treat a back-in-stock signup as one promise, not a list add

A back-in-stock alert should preserve the selected variant, available inventory, and the permission the shopper actually gave.

Skip this if

Stores that rarely go out of stock, where the diagnostic in this lesson should return a clear skip
new-brand-launcher at pre-launch: no out-of-stock traffic exists to recover

The decision: treat a back-in-stock request as permission for the restock communication described on the form, not as automatic permission for general campaigns. Preserve the selected variant, wait for inventory that can serve the shopper, and control how many people are notified when supply is limited.

Build this when unavailable products are expected to return and shoppers show repeated interest. No public dataset establishes a universal recovery rate or lift. Use store data to decide whether the system deserves its app cost and ongoing owner.