Hyrum's law

programming

With enough users, every observable behavior of your system will be depended on by somebody, contract or not.

Coined by Google engineer Hyrum Wright, the law explains why 'we never promised that' does not prevent breakage: users bind to timing, error strings, ordering, and undocumented quirks, so the de facto interface is everything observable. xkcd 1172 ('every change breaks someone's workflow') is its comic form. It is the deep reason behavior-preserving refactors still page someone at 3 a.m.

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