Spawn and manage Windows Terminal (wt.exe) windows and tabs from Node.js scripts and Claude Code hooks, with App Execution Alias resolution, correct CLI flags, and anti-patterns to avoid
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Spawn and manage Windows Terminal (wt.exe) windows and tabs from Node.js scripts and Claude Code hooks, with App Execution Alias resolution, correct CLI flags, and anti-patterns to avoid
["Always use cmd.exe /c wt or PowerShell Start-Process — never spawn wt.exe directly","Always use -w new to open a new window, not a tab in the user's current WT session","Always use shell:false with array args (no shell injection risk)","Always call child.unref() after detached spawn"]
error_handling
graceful
source
builtin
trust_score
100
provenance_sha
a39356dd7d195fe7
Windows Terminal Skill
Expert in spawning and managing Windows Terminal (wt.exe) from Node.js scripts,
hooks, and agents. Covers App Execution Alias resolution, full WT CLI syntax,
reliable spawn patterns, and anti-patterns to avoid.
- Explain why wt.exe cannot be spawned directly from Node.js child_process
- Provide the two reliable alternatives (cmd.exe /c wt, PowerShell Start-Process)
- Full WT CLI syntax: all options, subcommands, flags, command chaining
- Detect Windows Terminal at runtime (WT_SESSION env var)
- Implement detached interactive session spawning (used by shift-change Phase 4)
- Security-safe spawn patterns (shell: false, array args, no injection)
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.
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
// ❌ CommandNotFoundException — wt.exe alias not on Node.js child process PATHspawn('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 sessionspawn('cmd.exe', ['/c', 'start', '', 'wt', '-w', 'new', 'new-tab', 'cmd', '/k', 'claude']);
// ❌ shell: true — exposes shell metacharacter injection attack surfacespawn('cmd.exe', ['/c', 'wt', '-w', 'new', 'new-tab', userInput], { shell: true });
// ❌ spawn({detached:true}) in hooks — Windows kills child when hook exitsspawn('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 aliveconst 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 filestry {
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:
cmd.exe /c bat runs the bat synchronously
wt or start inside the bat creates a process in a NEW process tree
The bat returns immediately after wt/start fires
The new process is NOT in the hook's job object — it survives
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:
functionisPidAlive(pid) {
try {
process.kill(pid, 0); // signal 0 = existence check only, no killreturntrue;
} catch (_) {
returnfalse; // 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
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.
*/functionsanitizeWtArg(value) {
if (typeof value !== 'string') return'';
// Allow alphanumeric, spaces, hyphens, underscores, dotsreturn value.replace(/[^a-zA-Z0-9 \-_.]/g, '').slice(0, 64);
}
</execution_process>
<best_practices>
Use cmd.exe /c wt as primary: Simpler and more reliable than PowerShell Start-Process. No escaping issues with semicolons in command chaining.
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.
shell: false always: Prevents shell injection. Pass all arguments as array elements, never as a concatenated string.
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.
Sanitize user-supplied arguments: Tab titles and profile names from external sources must be sanitized before passing to WT CLI args.
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.
// 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 windowspawn('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
functionreportTerminalStrategy() {
if (process.platform !== 'win32') {
console.log('Unix: use gnome-terminal / xterm / konsole');
} elseif (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.
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