"Now, in order to understand the composition, you need to trace the thread through the entire system" I don't think that's necessarily true. It depends on the

"Now, in order to understand the composition, you need to trace the thread through the entire system" I don't think that's necessarily true. It depends on the implementation. In an actor based system, the syntax might not change that much. You just sprinkle in some async() here and some yield() there. So the code still looks like it is using function calls, and uses the stack/instruction pointer for state management, but is running asynchronously. I do very much agree with you point about coupling.