TL;DR
The most expensive bug I hit yesterday wasn't a crash. It was a stub that answered politely.
Four shapes of the same problem: a column nobody writes to, a model nobody calls, an engine backed by a fake, and a resolver that falls back to a null implementation silently.
The fix isn't "delete the fakes". Fakes are how you ship in slices. The fix is making which parts are real an enumerable question instead of a code-reading exercise.
Corollary that keeps paying off: null means unknown, not zero. An unreachable provider is not a cluster that shrank to nothing.
