That's a good point Scott. Asynchronous clock domains are indeed complex and it took us time to manage them efficiently. When you need to connect different clock domains with Cx/ngDesign you have to synchronize the various tasks with specific components (e.g. SynchronizerMux) http://cx-lang.org/documentation/instantiation/stdlib. Simulating the interactions between the domains is not yet supported by our simulator. We will develop this feature when people will request it. And you know, we're a startup so we still have plenty of R&D to do :-)