Thirty student screens, one page of thumbnails

In a physical lab, you walk the rows and glance at screens. In a remote course, that instinct usually dies: until you remember each student's desktop has a thumbnail endpoint.

Your monitor page polls GET /thumbnail/last on all thirty displays. Thumbnails are 320px instead of full 1920px frames, so the whole grid refreshes in a blink without flooding anyone's connection. One page, thirty live miniatures of thirty containers.

Frame eleven has been frozen on the same error dialog for ten minutes. You click it, open that student's display URL with sharing enabled, and you're standing at their desk: pointing at the actual screen, fixing the actual problem.

Walking the rows of a lab is now a page refresh.