FableOS

A complete desktop operating system that runs in your browser tab.

Kernel, persistent file system, window manager, terminal with a real shell, and thirteen applications — built entirely from scratch in TypeScript with zero runtime dependencies. The only things in package.json are Vite and the TypeScript compiler.

Run it

npm install
npm run dev          # → http://localhost:5173

Production build (static files, host anywhere):

npm run build        # outputs dist/ (~42 KB JS gzipped)
npm run preview      # → http://localhost:4173

What's inside

Layer	What it does
Kernel (src/core/kernel.ts)	App registry, process table with PIDs, launch/kill lifecycle, system power actions
VFS (src/core/vfs.ts)	Full virtual file system held in memory, persisted to IndexedDB (localStorage fallback). Files survive reboots
FableWM (src/ui/wm.ts)	Dragging, 8-direction resizing, edge snapping (left/right halves, top to maximize) with live preview, minimize/maximize animations, focus and z-order
Shell UI (src/ui/)	Boot sequence, lock screen, shutdown screen, desktop with icons and wallpapers, taskbar with tray + calendar, start menu with app/file search, context menus, dialogs, toast notifications

Applications

• Terminal (FableTerm/fsh) — a real shell: pipes |, redirection > >>, && chaining, quoting, ~/$VAR expansion, tab completion, persistent history, ~40 commands (ls, grep, tree, ps, kill, neofetch, cowsay, js, curl, …)
• Files — grid/list views, breadcrumbs, cut/copy/paste across windows, drag-&-drop moves, rename/delete/properties, import from and export to your real computer
• Scribe — text editor with line numbers, dirty tracking, Ctrl+S, save-as via system file picker, live Markdown preview
• Voyage — browser that renders .html files from the VFS in a sandboxed frame (scripts run!) plus embeddable real-web sites
• Paint — pen/eraser/shapes/flood-fill/eyedropper, undo/redo, saves PNGs into the VFS
• Calculator — hand-written expression parser (no eval), history tape
• Viewer — image viewer with zoom and set as wallpaper
• Keys — two-octave WebAudio synth piano with keyboard mapping and a demo song
• Minesweeper & Snake — first-click-safe sweeping; high scores persist
• System Monitor — process table with End-task, CPU/heap charts, FPS
• Settings — themes (dark/light), accent colors, wallpapers, identity, storage usage, factory reset
• Welcome — first-boot tour

Things to try

neofetch                         # system info with ASCII art
echo "hi" > ~/notes.txt          # then find it in Files
ls /bin | grep e                 # pipes work
tree ~                           # the whole home directory
open ~/Pictures/aurora.svg       # opens the Viewer
js [1,2,3].map(x => x*2)         # inline JavaScript
panic                            # do not run panic

• Drag a window against the screen edges to snap it; double-click a title bar to maximize.
• Ctrl+Alt+T opens a terminal anywhere.
• Right-click everything — desktop, files, taskbar buttons.
• Reload the tab: your files, wallpaper, history and high scores are still there.
• Settings → System → Reset FableOS wipes the disk and reboots to the factory image.

Architecture notes

• Everything is DOM + CSS; no canvas-rendered UI, no frameworks. A ~40-line h() helper builds all UI.
• The whole FS tree lives in memory for synchronous reads; every mutation debounces a persist into a single IndexedDB record.
• Apps are plain manifests: { id, name, icon, window, launch(ctx) }. The kernel creates the window, the app renders into ctx.root and registers cleanups with ctx.onClose().
• All icons are inline SVG — no emoji or icon-font dependencies, renders the same everywhere.

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Built from an empty directory by Fable 5 (Claude), Anthropic's AI — kernel to cowsay, in one session.