How does Ruby fiber scheduling integrate with event loops in modern concurrency models?

Fibers act as lightweight coroutines scheduled cooperatively by an event loop (scheduler).

Ruby 3 introduced non-blocking fiber scheduling where blocking operations are intercepted and handed to a scheduler (like IO reactor). Fibers yield control when waiting for I/O, allowing other fibers to run. This creates an async runtime without explicit async/await syntax. The scheduler manages ready/waiting fiber queues.