Safe Discount Stacking

Safe discount stacking is the margin-aware answer to a problem most stores solve badly in one of two directions: either they forbid combining codes entirely (a conversion tax that frustrates legitimate customers who hold a welcome code and a loyalty code), or they allow naive stacking where any technically valid combination goes through. Naive stacking is a silent margin leak. Each discount validates its own code in isolation, nobody checks the cumulative depth, and a customer ends up stacking three codes into a negative-margin order that the checkout happily accepts because every individual code was 'valid.' Safe discount stacking inverts the logic: combining is allowed by default, but the resulting margin is checked against a floor. It is implemented at two layers. Inside checkout, Shopify's discount combination settings decide which discount classes may combine, and a discount Function can implement best-offer-wins logic, removing the lowest-value code so the customer keeps the offer that matters most to them. After the order is placed, a per-order margin check covers what combination rules cannot see: Agentis computes the order's true net margin, after every applied code plus live COGS, freight, fees, and FX, within 60 seconds, and flags the order or holds it before fulfillment if the stack landed below floor. The two layers reinforce each other: the post-order records show which permitted combinations keep producing below-floor orders, which tells the merchant exactly which combination settings to tighten. This is materially better than the naive-versus-forbidden binary: it preserves the conversion benefit of generous stacking on healthy-margin orders while making sure the few orders that cannot afford the stack do not ship unreviewed. Connection to adjacent concepts: safe discount stacking is the controlled complement to discount stacking and coupon stacking, which describe the uncontrolled versions of the same behavior; it is a core pattern within promo margin governance; and it is one of the most direct levers against margin leakage, because uncontrolled stacking is a leading cause of preventable per-order margin loss on promotional traffic.