Deterministic PrestaShop Discount Simulation for Margin Safety

# Deterministic PrestaShop Discount Simulation for Margin Safety Promotion debugging becomes expensive when the same scenario produces an explanation nobody can reproduce. A deterministic simulator fixes the order of evaluation, normalizes inputs, and records every applied or skipped step. For a useful preflight model, catalog rules run before cart rules. Catalog rules are ordered by a stable ID, while cart rules are ordered by ascending priority and then ID. The model evaluates time, minimum value, quantity, currency, country, customer group, carrier, and product scope. Compatibility is checked against already-applied cart rules. Identical configuration and inputs must return identical steps and totals. Margin protection needs a cost reference. Enter a representative merchandise total and its estimated cost basis. After every applicable reduction, compare the final total with that cost basis. A below-cost result is a guardrail alert, not an accounting calculation: taxes, shipping price, gifts, product-level allocation, customer history, and third-party hooks can still change checkout behavior. This is why deterministic simulation complements rather than replaces a real storefront test. Its advantage is traceability. When a final total surprises the campaign owner, the replay shows the exact stage, rule, priority, before value, after value, and reason. [Vamao PrestaShop Discount Collision OS](/products/vamao-prestashop-discount-collision-os) keeps that workflow read-only. It maps likely interactions, replays representative scope, and exports a bounded review record without becoming another promotion authority.