Notion is a tiling, tabbed X11 window manager for keyboard-centric users, forked from Ion3. It provides a modular architecture with a C core (ioncore) and loadable modules (tiling, menu, query, statusbar, dock, multihead, etc.). Lua is the primary configuration and extension language, powered by the libextl library which auto-generates C-to-Lua bindings from annotated function declarations. The window manager manages a hierarchical region model (frames, workspaces, groups, clients) with dynamic dispatch via function tables. It includes a full-featured status bar system with a separate daemon (ion-statusd) and dozens of user-contributed meter scripts. Session management via XSMP, multi-monitor support (Xinerama/XRandR), and a remote-control socket (notionflux) are built-in. The codebase is mature but shows signs of technical drift: it relies exclusively on X11 (no Wayland), bundles a portable snprintf from 2000, carries legacy workarounds for long-obsolete systems, and many contrib scripts are unmaintained or broken. Nevertheless, the core architecture and utility libraries (libtu, libextl, libmainloop) are well-crafted and potentially reusable in other C projects.