This may be slightly more relevant to a more generic channel, but what’s the best way of requiring/importing duct.database.sql/Boundary to extend via extend-type? A problem I consistently run into is a require of just [duct.database.sql] will be removed by namespace-cleaning functionality of clojure refactor/etc.

That sounds like a bug in Clojure refactor, @dadair.

Requiring a namespace and using the type from it is the way to use record types in Clojure.