... hurts SEO or tracking: a noindex appears, a canonical or redirect shifts, a GA/GTM tag disappears, or AI crawlers get blocked. The hard part wasn't detection, it was false alarms. Testing on real sites turned up pages with tworobots tags where the noindex was in the second one, and firewalls returning 403s that looked like broken pages. Both are fixed. Launching here soon. Feedback welcome, especially from people who work at agencies ...