A polished redesign can lose organic traffic when URLs, indexation and metadata are treated as last-minute details.
Map old and new URLs
Prepare one-to-one redirects for valuable pages and remove chains, loops and accidental soft 404 responses.
Control indexation
Check canonicals, robots directives, XML sitemaps, language alternates and staging restrictions before opening the site.
Verify the rendered page
Titles, descriptions, headings, structured data and internal links should be checked in the final templates with real content.
A useful next step
Turn the observations into a short list of decisions with an owner, expected outcome and realistic priority.