How does Ruby fiber scheduling differ from OS thread scheduling?

Fibers are cooperative coroutines scheduled in user space, unlike preemptive OS threads.

Fibers in Ruby are lightweight execution contexts managed by the VM. Unlike threads, fibers require explicit yielding. With modern fiber schedulers (Ruby 3), fibers can simulate asynchronous I/O concurrency by integrating with event loops. Scheduling is cooperative, meaning control switches only at yield points or blocking operations.