> Positing that reducers should be pure is fine and dandy, telling me I can't throw in a side effect is none of your business. API contracts work in both ways.

> Positing that reducers should be pure is fine and dandy, telling me I can't throw in a side effect is none of your business. API contracts work in both ways. The user has to uphold it just as much as the provider. If you don't breakage ensues. In lower-level languages this can include the nasal demons from UB.