[Windows] Statusline and hook commands spawn bash.exe without CREATE_NO_WINDOW, causing visible console flash every ~10 seconds

Summary

On Windows, Claude Code runs statusline commands and hook commands (e.g. Stop hook) by spawning bash.exe as an intermediary shell. That bash process is created without the CREATE_NO_WINDOW flag, so a console window (managed by conhost.exe) briefly flashes on screen every time the status bar updates — typically every 10 seconds.

Environment

• OS: Windows 11 Home 10.0.26200
• Claude Code: latest (autoUpdatesChannel: latest)
• Shell: Git Bash (bash.exe from C:\Program Files\Gitin\)
• Settings: statusLine type command, Stop hook type command

Steps to reproduce

Configure a statusline command in .claude/settings.json:

{
  "statusLine": {
    "type": "command",
    "command": "C:/path/to/pythonw.exe C:/path/to/statusline.py"
  }
}

Every time Claude Code updates the status bar, a brief dark console window flashes on screen. The flash lasts for the entire execution time of the command (~200ms for a typical Python script; even bash -c "cat file.txt" produces a ~76ms flash because bash itself creates and destroys a console window).

Root cause (confirmed via WMI process monitoring)

Claude Code spawns the following chain on every statusline tick:

claude.exe
  └── bash.exe  (Windows creates conhost.exe for this — the flash)
        └── pythonw.exe statusline.py

WMI __InstanceCreationEvent monitoring captures this on every tick:

SPAWN  conhost.exe  PID=12456
       parent=<statusline runner>
       cmd: \??\C:\WINDOWS\system32\conhost.exe 0x4

SPAWN  bash.exe  PID=21940
       parent=<statusline runner>
       cmd: C:\Program Files\Gitinash.exe -c <statusline command>

If bash.exe were spawned with CREATE_NO_WINDOW (Win32 flag 0x08000000), Windows would create a hidden console host and no window would flash. The same issue occurs with hook commands (Stop hook, etc.).

What I tried

• Switching from python.exe to pythonw.exe (GUI subsystem) — flash persists because bash.exe itself creates the console
• Minimising script execution time (reducing from ~400ms to ~200ms) — reduces flash duration but does not eliminate it
• Compiled a .NET 6 binary to replace Python — same result (~200ms), since the bash overhead is the bottleneck
• Minimum achievable with current architecture: bash -c "cat file" = ~76ms, still visible

Expected behaviour

Console commands invoked for statusline / hooks should not produce any visible window. This is standard practice for background processes on Windows.

Proposed fix

In the Node.js code that spawns statusline/hook subprocesses, add windowsHide: true to the spawn options:

// child_process.spawn / exec / execFile
const child = spawn(shell, ['-c', command], {
  windowsHide: true,   // sets CREATE_NO_WINDOW on Windows — one line fix
  // ... other options
});

windowsHide: true is a built-in Node.js option that internally sets CREATE_NO_WINDOW when calling CreateProcess on Windows. This single flag change would eliminate all console flashing for statusline and hook commands.