Sharon Rosner's wroclove.rb 2026 talk introducing UringMachine, his Ruby gem that combines fibers with Linux io_uring for concurrent IO. Covers: (1) Fibers — suspendable/resumable execution contexts, initially wired together with Fiber#transfer, evolving to a run-queue abstraction and a fiber_switch method; (2) IO-aware fiber switching — fibers register intent to perform IO and only when the run queue is empty does the scheduler block on IO.select; (3) io_uring — Linux-specific async IO interface with submission queue (SQ), completion queue (CQ), and user_data tagging; three-phase ops (submission, execution, completion); the io_uring_enter syscall wrapped by io_uring_submit; (4) Combining fibers with io_uring — a 'machine' is an io_uring instance plus a run queue, with fibers re-queued when their CQE arrives; (5) UringMachine features — low-level API over raw FDs + buffers, IO class with buffered reads, fiber scheduler implementation, cancellation via scheduling exceptions, universal timeouts, graceful shutdown via exceptions, multi-shot accept/timeout/read/receive, provided buffers with incremental consumption for fully automatic buffer management, segmented (linked-list) buffers to avoid copy/alloc, synchronization primitives built on futex (mutexes, queues), OpenSSL integration via a custom BIO (with a PR open on the OpenSSL gem competing with one from a maintainer), pidfd and inotify support; (6) Benchmark with 50 Unix pipe pairs showing threads vs async vs UringMachine fiber scheduler vs UringMachine low-level API — advantage grows with concurrency, but the scenario is synthetic and pure-IO. Caveat: real Rails apps are CPU-heavy (refers audience to Jean Boussier's 'The Mythical IO-Bound Rails App'). Current uses: proof-of-concept Rack server running Rails, Syntropy web framework, closed-source time-series platform, converting legacy EventMachine apps. Roadmap: IPv6, batch-processing DSL, HTTP/1, HTTP/2, PostgreSQL wire protocol (Redis protocol already works), and integration with Rails/Hanami/Sidekiq. Q&A covered backlog limits on multi-shot accept, not using Falcon, and the EventMachine-replacement motivation.