At Oblong Industries one of the basic building blocks of everything we built was a homegrown C-based IPC system called Plasma. The message channel was an mmap'd file used as a ring buffer. All messages were human-readable, performance was good, configuration was trivial.

What was especially useful (and unusual in IPC systems it seems) was the property that message channels outlive all readers and writers, and even survive reboots, because they're just files. For local IPC you don't need a broker or server process.

All the engineers who ever worked at Oblong loved Plasma, so I've recreated and updated it, as Plasmite.

It's written in Rust and the message format is JSON, but it's fast because it's based on lite3 (https://lite3.io/index.html), a really cool project you should also check out.

Bindings for Python, Go, Node, and C, but you can also get a lot done with just the CLI tools. The basic commands are - "feed" (to write) - "follow" (to tail) - "fetch" (to read one) - "duplex" (to have a 2-way session)

I think duplex could be great for agent-agent communication, but I haven't tried this much yet. If you do, let me know!