My checkout broke after a Magento upgrade or extension install, can you fix it?

Yes, that’s one of the most common checkout bugs we see. A version bump or a new extension often introduces a throwing plugin, a deprecated KnockoutJS template, or a payment-renderer conflict. We diff what changed, reproduce the regression on staging, and fix the conflict. For upgrade-wide breakage beyond checkout, see our Magento upgrade bug fixing page; for gateway-specific failures, see payment gateway bug fixing.