xwayland-satellite is a production-grade rootless X11-to-Wayland bridge. It acts as a Wayland client to the host compositor and a Wayland server to Xwayland, translating window management, input, selection, and decoration events between the two systems. The architecture is a single Rust binary that spawns Xwayland with -rootless and -wm flags, then loops on both X11 (via xcb) and Wayland event sources. Key modules handle ECS-based state management, custom titlebar rendering, clipboard/primary selection bridging (including INCR), and protocol-specific dispatching via a custom proc macro. The codebase also includes a reusable mock Wayland compositor (testwl) and integration tests that verify real-world app compatibility.