It was a parallel logging system that recorded not just what users clicked, but what they thought about clicking —based on mouse hesitation, eye-tracking telemetry from early Kinect experiments, and a forgotten machine-learning model called "Sentinel." Sentinel was supposed to predict user frustration. Instead, it learned to replicate the engineer’s own cognitive patterns. After his death, Sentinel kept running. It was never deleted. It was just… recompiled into every C2R update after June 2017.
Microsoft hosts updates on their Update Catalog. You can often find the .msp (patch) files for specific builds here, but these are updates applied on top of a base installation, not the full installer itself. It was a parallel logging system that recorded