[cogman10]

For VM languages no problem, all those languages will support threads or using threads.

For non-VM interopt it will block the carrier thread if a native call causes any sort of blocking.

In Java, external to the VM calls are almost non-existent so it's not much of an issue. Likely you'd do those sorts of calls as regular kernel threads instead of the Loom virtual threads.

[int_19h]

To clarify, by interop here I don't just mean calling foreign functions. I mean calling async foreign functions. When async is explicit, it's easy to handle it on ABI level - it's just a bunch of callbacks (or abstractions wrapping them, like tasks/futures).

For example, suppose you're writing a Windows desktop app, and you decide to do so in Java. Modern Windows APIs are async. How would you asynchronously invoke such an API? In C#, you'd just use await.