Currently popular notions of types, such as signature compatibility, fail to express essential properties of concurrent active objects that are necessary for their correct use in new contexts. We propose and explore a new notion of compatibility called interaction conformance defined in terms of the possible interactions between an object and its clients. We relate interaction conformance to known equivalence relations between communicating concurrent agents, and we show that, by viewing types as certain kinds of indeterminate agents, interaction conformance gives us a subtype relationship. We briefly explore the potential for applying these ideas to concurrent object-oriented languages.