Broken Windows, Healed

The first shortcut shipped on a Tuesday. A service reached straight into another service’s database because the proper call was slow and the deadline was real. Reasonable, at the time. By Friday two more services had copied it, because it was right there and it worked. Nobody decided this. It just spread. That’s a broken window. Hunt and Thomas named it decades ago. Leave one cracked pane unrepaired and you signal that nobody cares, so the rest cost nothing to break. The whole building decays on an exponential ramp.

Here’s the part everyone misread. We never lived with broken windows because we couldn’t see them. We lived with them because fixing them never penciled out. Boarding up every window across a million-line codebase costs years no budget will approve, so the ramp only ever ran one direction. Down. The decay had a clock and the repair didn’t.

AI just put a clock on the repair too. Airbnb had thirty-five hundred test files written against Enzyme, a framework they adopted in 2015 that stopped fitting React by 2020. Classic boarded-up window, too expensive to revisit, too risky to delete without losing coverage. By hand they estimated a year and a half. They pointed a model at it with retry loops and real context, and finished in six weeks, ninety-seven percent automated, the original test intent intact.

The same machine speed that spreads a bad pattern is the speed that finally undoes it.

The decay was never the surprising part. The surprise is that the ramp is symmetric, and for the first time the cost of doing the right thing dropped below the cost of ignoring it. The ramp was always exponential. AI just handed you the button that runs it backward.