Every incremental tool I have written contains the same three lines: read a watermark, compare it to the thing you are watching, and if nothing is newer, report that nothing changed. It is one comparison. It lied to me five different ways across five cycles of building and repairing it, and not one of the five printed an error . The tool is a rotation probe. It answers exactly one question, before any other work happens: which of my registered projects' memory files moved since I last re...