@kattebak/sterk

Sterk is a terminal emulator for the web, built with ❤️ on top of Ace. It pairs Ace's mature text-rendering engine with a clean-room VT core, and treats shell-integration (OSC 133) as a first-class primitive rather than an extension.

Touch-friendly. Mobile-first. MIT.

Status

• ✅ M0 — Public API contract (src/types.ts)
• ✅ M1 — Foundation utilities (256-color palette, scrollback buffer, EventEmitter shim)
• ✅ M2 — Clean-room VT core (Paul Williams parser, SGR, OSC 133, Terminal factory)
• 🚧 M3 — Ace renderer glue (input, mouse, links, theme, DOM)
• ✅ M4 — Polish, alt-screen buffer, demo page, 1.0 release

See docs/ROADMAP.md.

Installation

npm install @kattebak/sterk

Size

Sterk is lightweight — under 53 kB packed (including Ace as a peer dependency).

Run npm run size to verify the current bundle size against the 75 kB budget.

Demo

A standalone demo is available in demo/index.html. To run it:

npm run build
npm run demo

Then open http://localhost:3000 in your browser.

Usage

Headless mode (parser + buffer only)

import { createTerminal } from '@kattebak/sterk';

const term = createTerminal({ cols: 80, rows: 24 });

term.write('Hello, world!\r\n');
term.write('\x1b[1;31mBold red text\x1b[0m\r\n');

term.onData((data) => {
  console.log('User input:', data);
  // Forward to backend (WebSocket, pty, etc.)
});

// Access buffer for rendering
const line = term.buffer.active.getLine(0);
console.log(line?.translateToString());

DOM mode (with Ace renderer)

import { createTerminal } from '@kattebak/sterk';

const term = createTerminal({
  cols: 80,
  rows: 24,
  theme: {
    foreground: '#f0f0f0',
    background: '#1e1e1e',
  },
});

// Attach to DOM
const container = document.getElementById('terminal');
term.open(container);

term.write('Welcome to sterk!\r\n');

// Register OSC 133 handler for shell integration
term.parser.registerOscHandler(133, (data) => {
  const kind = data.charAt(0); // 'A', 'B', 'C', 'D'
  if (kind === 'A') {
    console.log('Prompt start');
  }
  return false; // Allow other handlers
});

See demo/ for a complete standalone example.

Public API

• createTerminal(options?: TerminalOptions): Terminal — Create a terminal instance
• Terminal — Main terminal interface (write, resize, open, dispose)
• Parser.registerOscHandler(id, handler) — Register OSC sequence handlers
• Buffer / BufferLine / BufferCell — Read-only buffer access with full SGR attributes
• Theme — Color theme definition (foreground, background, ANSI palette)

See src/types.ts for full API documentation with JSDoc comments and examples.

Design principles

• Clean-room core. The VT parser is written from public specs (Paul Williams' state machine, XTerm Control Sequences, ECMA-48). No code lifted from other emulators.
• Ace does what Ace does well. Text layout, scrolling, theming — we don't reinvent it.
• OSC 133 first-class. Shell integration (prompt markers, command boundaries) is a built-in concept, not a bolt-on.
• Pragmatic feature scope. Feature parity with xterm.js is aspirational. We build what real consumers need and skip the rest.

License

MIT © 2026 Matthijs van Henten / kattebak