What if I just want self-hostable TypeScript actors _without agents_? I'm a long-time fan of Akka et. al., but to my knowledge Node never got a proper framework.

Hey! Rivet is pure actors at its core, there's nothing inherently specific to agents.

Instead, we provide an optional agent library that runs Pi Durable on top of actors (https://rivet.dev/agents/docs/quickstart/) or you can write your agent from scratch if you choose.