Cart Relay ‑ Persistent Cart

Shoppers browse on a phone and buy on a laptop. Cart Relay saves a signed-in customer's cart against their customer account and puts it back when they sign in on another device. No link to click, no code to enter. If the second device already has a cart, the two are combined: quantities of shared items add up and no line is dropped. Signing out clears that browser's cart and keeps the saved copy, so a shared computer stays private. Setup is one app embed in your theme — nothing to configure.