"GA4 shows a 40% cliff and GSC impressions match. You didn't ship anything."
Either a Google core update rolled out, a robots.txt / canonical change slipped through, or a site outage broke rendering for Googlebot.
Audit GSC coverage + impressions vs the update calendar. Diff robots.txt, canonicals and rendering for Googlebot. Fix at the template level, not per URL. Re-request indexing and monitor for 60 days.
Typical relief timeline: 5–10 days for diagnosis, 30–60 for recovery