Assumptions Do

There's a particular kind of silence before a large system fails. Not the silence of nothing happening — the opposite, actually. Everything is humming. Metrics are green. The on-call engineer is halfway through a cup of coffee. And somewhere in the stack, a belief that has been quietly wrong for eleven months is about to introduce itself. I've been in that silence enough times to stop blaming the proximate cause. When the postmortem gets written, it will name a culprit. An expired certificate. A deployment that bumped a queue depth past an undocumented limit. A retry storm that someone designed on purpose, for a topology that no longer exists. The culprit is real. The finding is technically accurate. And it misses the point almost entirely. What Actually Ages Software doesn't rot the way people mean when they say it rots. The bits don't degrade. What rots is the correspondence — the relationship between the system as built and the world it was built to operate inside. Every non-trivial