Agent Skills: Windows Terminal Skill

Windows Terminal Skill

The App Execution Alias Problem

wt.exe is a Windows App Execution Alias registered at %LOCALAPPDATA%\Microsoft\WindowsApps. App Execution Aliases:

• Work in interactive shells (cmd.exe, PowerShell terminal sessions)
• Are NOT resolvable from child_process.spawn() in Node.js
• Require the Windows shell infrastructure unavailable to child processes

User confirmed failure (2026-03-10):

PS C:\Users\oimir> wt.exe
# wt.exe : The term 'wt.exe' is not recognized...
# Even though WT_SESSION is set and wt works interactively

Reliable Approaches from Node.js

Approach A — cmd.exe /c start wt (PRIMARY — verified 2026-03-10): cmd /c start is the Windows built-in for launching GUI windows from non-interactive subprocess contexts (e.g. Claude Code hooks, piped processes). Plain cmd /c wt silently fails to produce a visible window from such contexts. The empty string '' is a required title placeholder for start when passing arguments to the target program.

Two additional requirements when spawning claude:

• Unset CLAUDECODE: Claude Code sets this env var; child claude processes detect it and refuse to start ("cannot be launched inside another Claude Code session"). Clear it in the cmd command with set CLAUDECODE= before invoking claude.
• cmd /k keeps the window open after the command finishes (useful for interactive use or -p print-mode demos). Use cmd /c if you want the window to close on exit.

// VERIFIED working from non-interactive subprocess (Claude Code hook, Bash tool, etc.)
spawn(
  'cmd.exe',
  [
    '/c',
    'start',
    '', // 'start' = Windows GUI window launcher; '' = required title placeholder
    'wt',
    '-w',
    'new',
    'new-tab',
    '--title',
    'My Title',
    'cmd',
    '/k',
    'set CLAUDECODE= && claude', // unset CLAUDECODE before launching claude
  ],
  { shell: false }
);
// Note: no detached/stdio/unref needed — 'start' fully detaches by design

Approach B — PowerShell Start-Process (alternative): Start-Process uses the Windows shell infrastructure to resolve aliases.

spawn(
  'powershell.exe',
  [
    '-NoProfile',
    '-Command',
    "Start-Process wt -ArgumentList \"-w new new-tab --title 'My Title' cmd /k 'set CLAUDECODE= && claude'\"",
  ],
  { detached: true, shell: false, stdio: 'ignore' }
);

Approach C — PowerShell Start-Process cmd (no WT required): Fallback when Windows Terminal is not installed or WT_SESSION is not set.

spawn(
  'powershell.exe',
  ['-NoProfile', '-Command', 'Start-Process cmd.exe -ArgumentList "/k claude" -WindowStyle Normal'],
  { detached: true, shell: false, stdio: 'ignore' }
);

WT CLI Syntax (from learn.microsoft.com, verified 2026-03-10)

wt [options] [command ; ]

If no command is specified, new-tab is used by default.

Global Options

| Option | Short | Description | | --------------- | ----- | -------------------------------------------------------------------------------------------- | | --window <id> | -w | Target window. new/-1 = always new window; 0/last = most recent; name = named window | | --maximized | -M | Launch maximized | | --fullscreen | -F | Launch fullscreen | | --focus | -f | Launch in focus mode | | --pos x,y | | Launch at position | | --size c,r | | Launch with columns/rows |

Subcommands

new-tab (nt)

wt new-tab [options] [commandline]
  -p <profile>          Profile name
  -d <dir>              Starting directory
  --title <text>        Tab title
  --tabColor <hex>      Tab color (#RGB or #RRGGBB)
  --colorScheme <name>  Color scheme override
  --suppressApplicationTitle
  --useApplicationTitle
  <commandline>         Command to run in the tab

split-pane (sp)

wt split-pane [options] [commandline]
  -H / --horizontal     Split horizontally
  -V / --vertical       Split vertically
  -s / --size <float>   Pane size (e.g. 0.4 = 40%)
  -D / --duplicate      Duplicate current pane
  (+ same flags as new-tab)

focus-tab (ft)

wt focus-tab -t <index>   Focus tab by zero-based index

move-focus (mf)

wt move-focus <direction>
  # direction: up|down|left|right|first|previous|nextInOrder|previousInOrder

Command Chaining (Semicolons)

Commands are separated by ;. Escaping rules depend on the calling shell:

| Shell | Separator | Example | | -------------------------- | --------------------------- | -------------------------------------------------------------- | | cmd.exe | ; | wt new-tab cmd ; new-tab powershell | | PowerShell | `; (backtick-escaped) | wt new-tab cmd `; new-tab powershell | | PowerShell stop-parse | --% ; | wt --% new-tab cmd ; new-tab powershell | | Node.js (cmd.exe approach) | Array element ";" | ['/c', 'wt', 'new-tab', 'cmd', ';', 'new-tab', 'powershell'] |

Detection Pattern

/**
 * Determine Windows Terminal spawn strategy.
 * @returns {'windows-terminal'|'windows-cmd'|'unix'}
 */
function getWindowsSpawnStrategy() {
  if (process.platform !== 'win32') return 'unix';
  if (process.env.WT_SESSION) return 'windows-terminal';
  return 'windows-cmd';
}

Canonical Node.js Spawn Patterns

Open NEW window in Windows Terminal (primary use case)

const { spawn } = require('child_process');

/**
 * Open a new WINDOW in Windows Terminal running a command.
 * Uses cmd.exe /c wt — resolves App Execution Alias reliably.
 * -w new forces a new window (not a tab in the user's current WT session).
 *
 * @param {string} command - Shell command to run (e.g. 'claude')
 * @param {object} opts
 * @param {string} [opts.title='New Session'] - Tab title
 * @param {string} [opts.profile] - WT profile name (e.g. 'Windows PowerShell')
 * @param {string} [opts.startingDir] - Starting directory
 */
function spawnWtNewWindow(command, opts = {}) {
  const { title = 'New Session', profile, startingDir } = opts;
  const wtArgs = ['/c', 'wt', '-w', 'new', 'new-tab'];
  if (title) wtArgs.push('--title', title);
  if (profile) wtArgs.push('-p', profile);
  if (startingDir) wtArgs.push('-d', startingDir);
  wtArgs.push('cmd', '/k', command);

  const child = spawn('cmd.exe', wtArgs, {
    detached: true,
    shell: false,
    stdio: 'ignore',
  });
  child.unref(); // Do NOT wait for child — let it run independently
  return child;
}

// Usage:
spawnWtNewWindow('claude', { title: 'Claude New Session' });

Open new TAB in existing WT window (use -w 0)

function spawnWtNewTab(command, opts = {}) {
  const { title, profile } = opts;
  const wtArgs = ['/c', 'wt', '-w', '0', 'new-tab'];
  if (title) wtArgs.push('--title', title);
  if (profile) wtArgs.push('-p', profile);
  wtArgs.push('cmd', '/k', command);

  const child = spawn('cmd.exe', wtArgs, {
    detached: true,
    shell: false,
    stdio: 'ignore',
  });
  child.unref();
  return child;
}

Fallback: new cmd.exe window (no WT required)

function spawnCmdNewWindow(command, opts = {}) {
  const { windowStyle = 'Normal' } = opts;
  const child = spawn(
    'powershell.exe',
    [
      '-NoProfile',
      '-Command',
      `Start-Process cmd.exe -ArgumentList "/k ${command}" -WindowStyle ${windowStyle}`,
    ],
    { detached: true, shell: false, stdio: 'ignore' }
  );
  child.unref();
  return child;
}

Platform-aware spawn (shift-change Phase 4 pattern)

function spawnInteractiveSession(command, opts = {}) {
  const strategy = getWindowsSpawnStrategy();

  switch (strategy) {
    case 'windows-terminal':
      return spawnWtNewWindow(command, opts);
    case 'windows-cmd':
      return spawnCmdNewWindow(command, opts);
    case 'unix': {
      // Try common Unix terminal emulators in order
      const emulators = [
        ['gnome-terminal', ['--', ...command.split(' ')]],
        ['xterm', ['-e', command]],
        ['konsole', ['-e', command]],
      ];
      for (const [bin, args] of emulators) {
        try {
          const child = spawn(bin, args, { detached: true, shell: false, stdio: 'ignore' });
          child.unref();
          return child;
        } catch {
          /* try next */
        }
      }
      throw new Error('No suitable terminal emulator found on Unix');
    }
    default:
      throw new Error(`Unknown platform spawn strategy: ${strategy}`);
  }
}

Anti-Patterns — DO NOT USE

// ❌ CommandNotFoundException — wt.exe alias not on Node.js child process PATH
spawn('wt.exe', ['-w', 'new', 'new-tab', 'cmd', '/k', 'claude'], { shell: false });

// ❌ cmd /c wt (without 'start') — silently produces no visible window from non-interactive
//    subprocess contexts (Claude Code hooks, piped Bash, service processes)
spawn('cmd.exe', ['/c', 'wt', '-w', 'new', 'new-tab', 'cmd', '/k', 'claude'], { shell: false });

// ❌ Missing 'set CLAUDECODE=' — claude refuses to start inside another Claude Code session
spawn('cmd.exe', ['/c', 'start', '', 'wt', '-w', 'new', 'new-tab', 'cmd', '/k', 'claude']);

// ❌ shell: true — exposes shell metacharacter injection attack surface
spawn('cmd.exe', ['/c', 'wt', '-w', 'new', 'new-tab', userInput], { shell: true });

// ❌ spawn({detached:true}) in hooks — Windows kills child when hook exits
spawn('node', ['my-script.js'], { detached: true, stdio: 'ignore' }).unref();
// The hook runner's job object kills ALL descendants — detached does NOT escape it

// ❌ AppActivate("title") — hits wrong window when multiple instances exist
// WshShell.AppActivate "claude"  ← matches user's main session, not the new one

// ❌ .join('\n') for bat files — cmd.exe fails or garbles output
fs.writeFileSync(batPath, lines.join('\n'), 'utf8'); // MUST use '\r\n'

// ❌ title command in cmd — WT overrides with the running process name
// start "MyTitle" cmd /k "title MyTitle & claude"  ← WT ignores both titles

// ❌ Not calling child.unref() — Node.js waits for child to exit, keeps process alive
const child = spawn('cmd.exe', [...]);
// Missing: child.unref()

CRITICAL: Hook Process Tree Escape (discovered 2026-03-25)

Claude Code hooks run in a subprocess with a Windows job object. spawn({ detached: true }) does NOT escape the job object — Windows kills ALL descendants when the hook exits.

The ONLY reliable escape pattern

Write a .bat file, then execFileSync('cmd', ['/c', batPath]). Inside the bat, use wt or start to create processes in an INDEPENDENT process tree.

const { execFileSync } = require('child_process');
const fs = require('fs');
const path = require('path');

const batPath = path.join(tmpDir, '_launcher.bat').replace(/\//g, '\\');
fs.writeFileSync(batPath, [
  '@echo off',
  `wt -w 0 new-tab --title "MySession" -- cmd /k "cd /d "${rootWin}" && my-command"`,
  `del "%~f0" 2>nul`,
].join('\r\n'), 'utf8');  // MUST be \r\n for bat files

try {
  execFileSync('cmd', ['/c', batPath], {
    shell: false,
    timeout: 5000,
    stdio: 'ignore',
    cwd: ROOT,
  });
} catch (_) {
  // bat self-delete can cause non-zero exit — harmless
  // wt/start already fired before the delete ran
}

Why this works:

1. cmd.exe /c bat runs the bat synchronously
2. wt or start inside the bat creates a process in a NEW process tree
3. The bat returns immediately after wt/start fires
4. The new process is NOT in the hook's job object — it survives
5. del "%~f0" 2>nul self-cleans the bat file

Tab vs Window from hooks

@rem Opens a TAB in the most recent WT window:
wt -w 0 new-tab --title "MyTab" -- cmd /k "my-command"

@rem Opens a new WINDOW (use when you don't want to intrude on user's WT):
start "" /D "C:\mydir" cmd /k "my-command"

VBScript Window Targeting by PID (discovered 2026-03-25)

When sending keystrokes to a specific window (e.g., auto-accepting a confirmation prompt), you MUST target by PID. Window titles are unreliable because:

• WT overrides title command and start title with the running process name
• Multiple windows may have the same title (e.g., two "claude" sessions)

WMI query to find exact process, then AppActivate by PID

WScript.Sleep 4000
Set wmi = GetObject("winmgmts:\\.\root\cimv2")

' Find cmd.exe with a unique marker in command line
Set procs = wmi.ExecQuery( _
  "SELECT ProcessId FROM Win32_Process " & _
  "WHERE Name='cmd.exe' AND CommandLine LIKE '%MyUniqueMarker%'")
Dim targetPid: targetPid = 0
For Each proc In procs
    targetPid = proc.ProcessId
    Exit For
Next

' Fallback: newest cmd.exe
If targetPid = 0 Then
    Set procs2 = wmi.ExecQuery( _
      "SELECT ProcessId, CreationDate FROM Win32_Process WHERE Name='cmd.exe'")
    Dim newest: newest = ""
    For Each proc In procs2
        If newest = "" Or proc.CreationDate > newest Then
            newest = proc.CreationDate
            targetPid = proc.ProcessId
        End If
    Next
End If

If targetPid > 0 Then
    Set WshShell = WScript.CreateObject("WScript.Shell")
    WshShell.AppActivate CLng(targetPid)
    WScript.Sleep 500
    WshShell.SendKeys "{ENTER}"
End If

Launch the VBScript from the same bat that spawns the terminal:

@echo off
wt -w 0 new-tab --title "MySession" -- cmd /k "my-command"
start "" wscript "C:\path\to\_auto-accept.vbs"
del "%~f0" 2>nul

Lockfile Deduplication for Hooks

Hooks fire on every UserPromptSubmit. Use atomic O_EXCL lockfile to prevent spawning multiple windows:

const LOCKFILE = path.join(runtimeDir, 'my-cooldown.lock');
const COOLDOWN_MS = 120000; // 2 minutes

let alreadyLocked = false;
try {
  // wx = O_CREAT | O_EXCL — fails atomically if file exists
  fs.writeFileSync(LOCKFILE, String(Date.now()), { flag: 'wx' });
} catch (e) {
  if (e.code === 'EEXIST') {
    try {
      const lockTime = parseInt(fs.readFileSync(LOCKFILE, 'utf8').trim(), 10);
      if (!isNaN(lockTime) && Date.now() - lockTime < COOLDOWN_MS) {
        alreadyLocked = true;
      } else {
        fs.writeFileSync(LOCKFILE, String(Date.now()), 'utf8'); // Expired
      }
    } catch (_) {
      fs.writeFileSync(LOCKFILE, String(Date.now()), 'utf8'); // Corrupt
    }
  }
}
if (alreadyLocked) process.exit(0);

PID Alive Check (cross-platform)

function isPidAlive(pid) {
  try {
    process.kill(pid, 0); // signal 0 = existence check only, no kill
    return true;
  } catch (_) {
    return false; // ESRCH = no such process
  }
}

Bat File Requirements

CRLF line endings are MANDATORY

// WRONG — cmd.exe fails silently or produces bizarre errors with LF
fs.writeFileSync(batPath, lines.join('\n'), 'utf8');

// RIGHT — CRLF required for all .bat and .cmd files
fs.writeFileSync(batPath, lines.join('\r\n'), 'utf8');

Bash vs cmd escaping trap

When testing from Git Bash (Claude Code's default shell on Windows), cmd /c path\to\file.bat fails because bash interprets \t as tab, \n as newline, etc.

# WRONG from Git Bash — bash eats backslashes
cmd /c C:\path\to\file.bat

# RIGHT — use forward slashes or run from Node.js
cmd /c "C:/path/to/file.bat"

Best practice: Always use execFileSync('cmd', ['/c', batPath]) from Node.js. Node handles backslash paths correctly.

Quick Reference: Anti-Pattern Table

| Pattern | Problem | Fix | |---------|---------|-----| | spawn({detached:true}) in hooks | Windows kills child on hook exit | Write bat + execFileSync | | AppActivate("title") | Multiple windows match | Target by PID via WMI | | start "Title" cmd /k from hook | Opens new window, not tab | wt -w 0 new-tab -- in bat | | .join('\n') for bat files | cmd.exe fails | .join('\r\n') (CRLF) | | cmd /c path\file.bat from bash | Bash eats backslashes | Use Node.js execFileSync | | title MyTitle in cmd | WT overrides with process name | Don't rely on titles, use PID | | process.exit(1) to block hook | Exit 1 = error, NOT block | Use process.exit(2) |

Related Files (agent-studio)

• .claude/hooks/channels/channel-auto-start.cjs — Production hook using all patterns above
• .claude/tools/cli/channel-manager.cjs — Channel session lifecycle management
• .claude/tools/cli/terminal-tracker.cjs — PID tracking for spawned sessions
• scripts/channels/start-telegram.bat — Simple one-line launcher reference

Injection-Safe Argument Handling

When title or profile come from user-supplied or external data, sanitize before use:

/**
 * Sanitize a string for use as a WT --title or -p argument.
 * Strips shell metacharacters that could escape argument boundaries.
 */
function sanitizeWtArg(value) {
  if (typeof value !== 'string') return '';
  // Allow alphanumeric, spaces, hyphens, underscores, dots
  return value.replace(/[^a-zA-Z0-9 \-_.]/g, '').slice(0, 64);
}

</execution_process>

<best_practices>

1. Use cmd.exe /c wt as primary: Simpler and more reliable than PowerShell Start-Process. No escaping issues with semicolons in command chaining.

2. Always -w new for new windows: Without -w new, wt new-tab opens in the user's CURRENT WT session. This is confusing when triggering from a hook. Use -w new to guarantee a new, isolated window.

3. shell: false always: Prevents shell injection. Pass all arguments as array elements, never as a concatenated string.

4. child.unref() mandatory: Without unref(), the parent Node.js process (the hook) will wait for the terminal to close before exiting. This hangs the hook indefinitely.

5. Sanitize user-supplied arguments: Tab titles and profile names from external sources must be sanitized before passing to WT CLI args.

6. Check WT_SESSION before using WT-specific features: Some WT CLI flags (like split-pane, tabColor) are WT-only and fail in regular cmd.exe.

</best_practices>

<enforcement_hooks>

Input validated against schemas/input.schema.json before execution. Output contract defined in schemas/output.schema.json.

Pre-execute hook: hooks/pre-execute.cjs — validates required fields and platform checks. Post-execute hook: hooks/post-execute.cjs — emits observability event.

</enforcement_hooks> </instructions>

Example 1: Spawn a new Claude session in Windows Terminal (shift-change Phase 4)

const { spawn } = require('child_process');

// From spawn-new-session.cjs
const isWT = !!process.env.WT_SESSION;

if (isWT) {
  // cmd.exe resolves App Execution Alias
  const child = spawn(
    'cmd.exe',
    ['/c', 'wt', '-w', 'new', 'new-tab', '--title', 'Claude New Session', 'cmd', '/k', 'claude'],
    { detached: true, shell: false, stdio: 'ignore' }
  );
  child.unref();
} else {
  // Fallback: plain cmd.exe window
  const child = spawn(
    'powershell.exe',
    [
      '-NoProfile',
      '-Command',
      'Start-Process cmd.exe -ArgumentList "/k claude" -WindowStyle Normal',
    ],
    { detached: true, shell: false, stdio: 'ignore' }
  );
  child.unref();
}

Example 2: Open two panes in a new WT window

// Open a new WT window with two vertical panes: claude on left, PowerShell on right
// Note: semicolons in cmd.exe arrays require escaping as a string element ';'
spawn(
  'cmd.exe',
  [
    '/c',
    'wt',
    '-w',
    'new',
    'new-tab',
    '--title',
    'Claude',
    'cmd',
    '/k',
    'claude',
    ';',
    'split-pane',
    '-V',
    'powershell',
  ],
  { detached: true, shell: false, stdio: 'ignore' }
);

Example 3: Open a specific WT profile

// Open Windows Terminal with the 'Ubuntu' WSL profile in a new window
spawn('cmd.exe', ['/c', 'wt', '-w', 'new', 'new-tab', '-p', 'Ubuntu', '--title', 'WSL Session'], {
  detached: true,
  shell: false,
  stdio: 'ignore',
});

Example 4: Detect and report terminal strategy

function reportTerminalStrategy() {
  if (process.platform !== 'win32') {
    console.log('Unix: use gnome-terminal / xterm / konsole');
  } else if (process.env.WT_SESSION) {
    console.log('Windows Terminal detected — use cmd.exe /c wt -w new new-tab');
  } else {
    console.log('No WT — use PowerShell Start-Process cmd.exe');
  }
}

Enforcement Hooks

Input validated against schemas/input.schema.json before execution. Output contract defined in schemas/output.schema.json.

Search Protocol

For code discovery and search tasks, follow this priority order:

1. pnpm search:code "<query>" (Primary intent-based search).
2. Skill({ skill: 'ripgrep' }) (for exact keyword/regex matches).
3. Semantic/structural search via code tools if available.

Memory Protocol (MANDATORY)

Before starting: Read .claude/context/memory/learnings.md and .claude/context/memory/decisions.md.

After completing:

• New pattern → .claude/context/memory/learnings.md
• Issue found → .claude/context/memory/issues.md
• Decision made → .claude/context/memory/decisions.md

ASSUME INTERRUPTION: Your context may reset. If it's not in memory, it didn't happen.