SCR3 · the editor core. Every keystroke is routed through a CRDT model (scriptorium-kernel.js), never straight into the DOM — the page you see is a rendering of the model, which is what lets SCR5 merge two people typing at once. Marks live per-character, and block styles (headings, lists, quotes) and alignment live per-block, so formatting never clobbers a neighbour. Undo only ever undoes your edits. Documents save to this device; export gives you Markdown you can carry anywhere.