Eio

Leverages OCaml 5's effect system for direct-style code, eliminating monadic overhead and providing real stack traces, as shown in the motivation section where it's faster due to no heap allocations for simulated stacks.

Implements switches for resource management and cancellation, ensuring clean fiber and resource lifecycle, demonstrated in the switches section with Switch.run grouping fibers and releasing resources.

Offers generic APIs with optimized backends for Linux (io_uring), POSIX, Windows, and browsers, allowing high-performance I/O across different environments, as listed in the Eio packages.

Restricts resource access via lexical scoping for enhanced security and auditability, explained in the design note on capabilities where authority is passed explicitly through the env parameter.

Fibers within a domain are scheduled deterministically, aiding testing and debugging, as noted in the design note on determinism, making mock-based tests predictable.