M4uhdcc

They first saw it on a rain-slicked alley camera at 02:13 — a stuttering blur of code and light that seemed to fold the puddles into impossible angles. The caption the system spat out was nothing human would make: M4UHdcc. It arrived like a punctuation mark from somewhere machines keep secret. By morning, every feed had a pixel of it; by evening, someone had made a shrine of sticky notes and printed lines of alphanumeric worship.