Posting this here in case someone else is working on this:

I think the problem looks like:

node    → instantiate HooksProxy
          ↳ spawn InternalWorker
                   
app.js  → spawn Worker
          ↳ instantiate HooksProxy
            ↳ spawn InternalWorker

The various HooksProxys need to always connect to the same InternalWorker. I think the way to do that is to have the "main" MessageChannel::port2 (instantiated by node itself) available to the various HooksProxys. They use that to send their message to InternalWorker and include their own MessageChannel::port2 for InternalWorker to respond back (listening on their own MessageChannel::port1, not main's).

Each HooksProxy needs to instantiate its own lock and pass that to the (possibly existing) working.

PS Sorry, I may be getting the port numbers mixed up (documentation for these are always the most convoluted possible 😩). In the above, InternalWorker receives all messages (regardless of originating thread) on the same port; it then responds back to the originator's (own) provided port.

Fixed by #52706

For those of you subscribed to this thread, I just posted nodejs/loaders#201 to ask for your feedback on what direction you think this API should go.