Why not "kisafi"?
"Safi" does not have variation of declension (indeclinable adjective):
I think most words that are derived from other languages are like that - and afaik "safi" comes from arabic (please correct me if I'm wrong)
Hey Duolingo it is okay to say Kijiko safi but that is not commonly used in Tanzania where we say Kijiko Kisafi. I have notes and and explanations to teach you these forms of adjectives to be used with a Noun from KI/VI Noun Class.