Interesting project. Koka does have great interop with C code. An async library has existed in the past, and will likely be reintegrated soon. Unfortunately that will most likely be backed by the LibUV event loop which is not WASM compatible. However, Koka's delimited continuation machinery does not require stack suspension or stack swapping at all. All it requires is a bit of thread local state. Koka builds up continuations through a series of function pointers and closure state, and only when needed. So theoretically all you need is some sort of event loop.