Auto Add to Cart

The problem

A grocery store wants a paper bag added the moment anything lands in the cart, and a produce bag added whenever fruit or vegetables do, without a developer wiring up a one off script for each product launch. Doing this by hand, with observers scattered across the codebase, tends to break the first time a shopper adds items through the mini cart, a saved cart, or the REST API instead of the page the original script was written for.

How it works

A rule is four independent settings: what triggers it (any product, a SKU list, a category, or an attribute value), how much it adds (a fixed quantity, a ratio scaled to the trigger, or one unit per N trigger units), which product it adds, and whether a shopper is allowed to remove it or change its quantity. Rules are evaluated on every quote save, the one point every add, update and remove path in Magento eventually passes through, so a rule fires consistently no matter which storefront flow triggered the change.

What the store owner sees

Rules live in their own Auto Add Rules grid, not buried in Store Configuration, so building a new promotion (a free sample with every order over a category, a bag with every order) is a form to fill in, not a deployment. Each rule's shopper permissions are its own toggles, so a merchant can let shoppers remove a bag they do not want while still keeping a warranty card's quantity locked to what was actually purchased.

What the shopper sees

The accessory just appears in the cart when it should and disappears when it should not, at whatever quantity the rule calls for. If a rule allows it, removing the item themselves keeps it removed for that cart, so an unwanted accessory does not keep reappearing every time the shopper touches their cart again.