xterm-pty

name: xterm-pty description: xterm.js 6.0 + portable-pty terminal patterns for agentcockpit

xterm.js + PTY

Overview

agentcockpit uses xterm.js 6.0 for terminal rendering and portable-pty (Rust) for cross-platform PTY management. The PTY runs user's shell, and AI agents are launched as commands within it.

Configuration

• xterm.js 6.0 with addons: fit, clipboard, web-links, canvas/WebGL renderers
• portable-pty 0.8 (Rust crate)
• Terminal: TERM=xterm-256color, 10000 line scrollback
• Font: JetBrainsMono Nerd Font, 14px

Data Flow

User types → xterm.onData → usePty.write → ptyWrite IPC → Rust PtyManager.write → PTY master
PTY output → Rust reader thread (4096 byte chunks) → pty-output-{id} event → usePty.onData → xterm.write

Common Patterns

Spawning PTY (Rust)

// PtyManager::spawn creates PTY pair, spawns $SHELL
let pair = pty_system.openpty(PtySize { rows, cols, .. })?;
let mut cmd = CommandBuilder::new(shell);
cmd.cwd(cwd);
cmd.env("TERM", "xterm-256color");
// Clear nested detection vars
cmd.env_remove("CLAUDECODE");
cmd.env_remove("CLAUDE_CODE_ENTRYPOINT");
let child = pair.slave.spawn_command(cmd)?;

Writing to PTY (TypeScript)

import { ptyWrite } from '../services/tauriService';
await ptyWrite(ptyId, data);

UTF-8 Boundary Handling (Rust)

The reader thread buffers incomplete UTF-8 sequences across reads using find_utf8_boundary() to avoid splitting multi-byte characters.

Activity Detection

const { signalOutput, signalUserInput } = useTerminalActivity({
  terminalId,
  threshold: 3000, // ms of silence before "finished"
  onFinished: handleTerminalFinished,
});

Resume UUID Detection

// In TerminalView onData callback
const stripped = data.replace(/\x1b\[[0-9;]*[a-zA-Z]/g, ''); // Strip ANSI
resumeBufferRef.current += stripped;
const match = resumeBufferRef.current.match(
  /claude\s+--resume\s+([0-9a-f]{8}-[0-9a-f]{4}-...-[0-9a-f]{12})/
);
if (match) sessionEvents.emit('resume-detected', { uuid: match[1], terminalId });

Best Practices

1. Never block PTY writes — send input immediately, do async work (snapshots) after
2. Buffer incomplete UTF-8 in reader thread — don't emit partial sequences
3. SIGTERM then SIGKILL on close — give process group time to clean up
4. Guard 0x0 resize — happens when xterm container gets display:none
5. Use refs for listeners — prevent re-renders from killing event subscriptions