Record the baseline
Record theme, platform, plugin and custom-code versions. Back up files and data and verify a recovery method. Capture the homepage, listing, detail page and critical forms, plus one complete task journey. Theme files alone are generally not a complete website recovery plan.
Change a manageable set of variables
Read release notes in a test environment, identify migration steps and then update. Avoid changing the theme, payment extension and server configuration simultaneously; that makes regressions harder to diagnose. Keep logs and reproduction steps when something fails.
Recheck after deployment
After deployment, verify caches, signed-in behavior, forms, search and mobile navigation. Define rollback conditions and ownership. If rollback involves the database, do not overwrite real orders or member data created after deployment. Record both successful checks and unresolved issues.
