There is also CapnP’s moral ancestor CapTP[1]/VatTP aka Pluribus developed to accompany Mark Miller’s E language (yes, it’s a pun, there is also a gadget called an “unum” in there). For deeper genealogy—including a reference to Barbara Liskov for promise pipelining and a number of other relevant ideas in the CLU extension Argus—see his thesis[2].

(If I’m not misremembering, Mark Miller later wrote the promise proposal for JavaScript, except the planned extension for RPC never materialized and instead we got async/await, which don’t seem compatible with pipelining.)

The more recent attempts to make a distributed capability system in the image of E, like Spritely Goblins[3] and the OCapN effort[4], also try for pipelining, so maybe if you hang out on cap-talk[5] you’ll hear about a couple of other protocols that do it, if not ones with any real-world usage.

(And I again reiterate that, neat as it is, promise pipelining seems to require programming with actual explicit promises, and at this point it’s well-established how gnarly that can get.)

One idea that I find interesting and little-known from the other side—event loops and cooperatively concurrent “active objects”—is “causality IDs”[6] from DCOM/COM+ as a means of controlling reentrancy, see CoGetCurrentLogicalThreadId[7] in the Microsoft documentation and the discussion of CALLTYPE_TOPLEVEL_CALLPENDING in Effective COM[8]—I think they later tried to sell this as a new feature in Win8/UWP’s ASTAs[9]?

[1] http://erights.org/elib/distrib/captp/index.html

[2] http://erights.org/talks/thesis/index.html

[3] https://spritely.institute/goblins/

[4] https://github.com/ocapn/ocapn

[5] https://groups.google.com/g/captalk/

[6] https://learn.microsoft.com/openspecs/windows_protocols/ms-d...

[7] https://learn.microsoft.com/windows/win32/api/combaseapi/nf-...

[8] https://archive.org/details/effectivecom50wa00boxd/page/150

[9] https://devblogs.microsoft.com/oldnewthing/20210224-00/?p=10...