[thirtyseven]

By not having test cases for those specific domains, and by passing your input through some general purpose internal URL handling library that does more than you thought it did [1]. Neither is (very) surprising.

[1] https://rachelbythebay.com/w/2021/12/24/mkdir/

[duxup]

‘You know words have “co” in them’ seems like an easy thing to think of.