“Are we sure checkout isn't broken?” You don't actually know. Error tracking is quiet. RUM looks normal. The funnel dipped but won't say why. So you click through on desktop, then on mobile, then ask the user for a screen recording. Faultsense answers from the assertions you wrote, validated in real user sessions, per release, per cohort. Not a chart you have to read. A structured fact: assertion, release, cohort, pass/fail. Written like a test. Reported like a production signal. Per release, per cohort.