I see (and use) core.async as low level primitives from which to build higher level FRP, reactive, flow-based or message-based systems. For example, re-frame,

I see (and use) core.async as low level primitives from which to build higher level FRP, reactive, flow-based or message-based systems. For example, re-frame, zelkova (Elm-like thing in ClojureScript[1]) and others (eg the in-house thing I wrote before I came across re-frame) are implemented using core.async So, no, its not a substitute - its a (potential) building block. [1] https://github.com/jamesmacaulay/zelkova https://github.com/jamesmacaulay/zelkova