R&D on reactive programming is growing and this has delivered many language constructs, libraries and tools. Scala programmers can use threads, timers, actors, futures, promises, observables, the async construct, and others. Still it seems to us that the state of the art is not mature: reactive programming is relatively hard, and confidence in correct operation depends mainly on extensive testing. Better support for reasoning about correctness would be useful to address timing dependent issues. The Algebra of Communicating Processes (ACP) has a potential to improve this: it lets one concisely specify event handling and concurrency, and it facilitates reasoning about parallel systems. There is an ACP-based extension to Scala named SubScript. We show how it helps describing the internal behavior of Akka actors, and how it combines with futures. For more information see www.subscript-lang.org.