Move a subdomain into a subfolder — the migration checklist

Move a subdomain into a subfolder — the migration checklist
Client had the blog on blog.site.com, leaking authority. Moved it to site.com/blog/. The play:
— Crawl the subdomain fully, export every URL + its rankings as a baseline
— Build the 1:1 redirect map, subdomain path > subfolder path
— Stand up the subfolder version, internal-link it into main nav and footer
— Deploy 301s from every old subdomain URL
— Update canonical tags to the new subfolder URLs
— Submit new sitemap, keep the old subdomain sitemap live a few weeks so 301s get crawled
Blog traffic merged into the main domain's authority — rankings lifted across the board in ~8 weeks.
Don't kill the subdomain DNS until Search Console shows the 301s processed.