Sounds a lot like SPIN OS https://en.wikipedia.org/wiki/SPIN_(operating_system) They have to make do without type safety (in SPIN's case provided by modula-3), but it's really cool to see it tried. For those interested: SPIN and other hybrid kernels (like Exo) were created in the fall-out of "microkernels are bad" by attempting to allow a hybrid approach. Linux was created around the same time staying straight in the monolithic category (but since moving to be more hybrid).