ircd-hybrid is a high-performance, modular IRC daemon written in C. It implements the full IRC protocol (RFC 1459, 2812, 2813) with modern IRCv3 capabilities (account-notify, extended-join, etc.), server-to-server linking (TS6), TLS support (GnuTLS, OpenSSL, wolfSSL), and a dynamic module system via GNU libltdl. The architecture is event-driven with selectable I/O backends (epoll, kqueue, poll) and a self-contained I/O abstraction library (libio) that provides networking, DNS resolution, event timers, data structures (patricia trie, doubly-linked lists, dynamic buffers), and TLS abstraction. Configuration is parsed by a Bison/Flex-generated parser supporting a rich set of server options. The codebase is well-structured with a clear separation between core daemon, library, and loadable modules, making it extensible and maintainable. Originally forked from the hybrid IRCD project in 1997, it has evolved to support modern IRC standards while maintaining backwards compatibility.