No.
The cart drawer replaces the cart page only. Shopify checkout is unchanged.
What Oxify does
Replaces Shopify's default cart experience with a slide-out drawer. Adds reward progress bars, free gifts, FBT bundles, and other in-cart features.
What Oxify doesn't do
Touch checkout. Your customers go through Shopify's standard checkout flow exactly as before. Payment, shipping, taxes, fraud detection, and order placement are all Shopify-native.
The post-purchase exception
The post-purchase upsell module runs after checkout payment but before the thank-you page, using Shopify's official checkout_post_purchase extension API. It's not modifying checkout itself — it's an add-on layer Shopify provides.