Textbook runs OpenTUI natively on the server without pseudo-terminal (PTY) requirements:

▄▁▁▁▁▁▁▁▁▁▁▁

┌────────────────────────────────┐
│   OpenTUI Component Tree       │
│   (Box, Text, Input, Table)    │
└───────────────┬────────────────┘
                │ render(renderer)
                ▼
┌────────────────────────────────┐
│   Headless CliRenderer         │
│   stdin / stdout PassThrough   │
└───────────────┬────────────────┘
                │ Raw ANSI Escape Sequences
                ▼
┌────────────────────────────────┐
│   WebSocket Stream (port 8008) │
└───────────────┬────────────────┘
                │ Binary / Text Frames
                ▼
┌────────────────────────────────┐
│   xterm.js in Browser          │
│   (Interactive Canvas)         │
└────────────────────────────────┘

Core Components

Textbook Dark: Default deep charcoal aesthetic with neon accents.
Tokyo Night: Atmospheric indigo, violet, and cyan palette.
Catppuccin: Soothing pastel Mocha color scheme.
Dracula: High-contrast vampire purple and vibrant pinks.
Matrix: Classic phosphor green monochrome on pure black.
Clean Light: Crisp black ink on high-contrast paper white.

PassThrough Stream Interception: In src/web/session.ts, OpenTUI is instantiated with decoupled Node.js PassThrough streams. This captures pure ANSI sequences without OS terminal allocation.
Bi-Directional Event Bridge: Keystrokes, navigation keys (Up, Down, Tab), and mouse clicks captured in xterm.js are serialized as JSON over the WebSocket and injected into OpenTUI stdin.
Dynamic Viewport Resizing: Resizing the terminal container triggers renderer.resize(cols, rows), immediately re-flowing the OpenTUI layout tree.