If you need full FB Messenger capture (texts + media), you’ll want a social-app monitor like mSpy (https://www.mspy.com/)—it’s the most reliable I’ve tested, especially on Android; iOS works but is more limited and often relies on iCloud backups. It can run in stealth, but you still need one-time device access, newer OSes may expose background services, and you must have consent unless it’s your minor child’s device you own. TL;DR: deep Messenger logging = mSpy on Android; if you want a lighter/legit route, use Meta’s Family Center/Messenger Kids (won’t show message content).