GitHub Issue Draft: DesktopCommanderMCP pwsh stdout

Repo: wonderwhy-er/DesktopCommanderMCP
Title: start_process captures no stdout from external executables when defaultShell is pwsh.exe

Description

When defaultShell is set to pwsh.exe (PowerShell 7.5.4), start_process
captures zero stdout lines from any external executable (python, git, node,
etc.). The process exits with code 0 but all output is lost. Only pwsh-native
commands (Write-Output, echo) produce captured output.

Switching back to powershell.exe (5.1) immediately restores stdout capture
for all external executables.

Environment

• DC version: 0.2.38 (DXT/Electron)
• OS: Windows 11
• Node.js: 25.7.0
• pwsh: 7.5.4 (.NET 8)
• powershell.exe: 5.1.x
• Python: 3.14.3
• Git: 2.53.0

Steps to Reproduce

1. set_config_value defaultShell to pwsh.exe
2. start_process with python -c "print('hello')"
3. Observe: PID assigned, (shell: pwsh.exe) shown, but Initial output is empty
4. read_process_output: 0 lines, exit code 0
5. set_config_value defaultShell back to powershell.exe
6. Same command: output captured normally

Test Matrix

Key observation: A visible python.exe console window appears on the
desktop during pwsh tests, suggesting stdout is routed to a detached console
rather than DC's capture pipe.

Patches Attempted

Patch 1: Remove -Login flag

getShellSpawnArgs() uses ['-Login', '-Command', command] for pwsh.
Removed -Login so args become ['-Command', command].
Result: No fix. External exe stdout still not captured.

Patch 2: shell option + explicit stdio

Changed from spawn('pwsh.exe', ['-Command', cmd]) to
spawn(cmd, [], { shell: 'pwsh.exe', stdio: ['pipe','pipe','pipe'] }).
Result: npx cache regenerated on restart, wiping patch. Even if preserved,
the architectural issue likely remains.

Analysis

The issue appears to be in how Node.js child_process.spawn() handles stdio
inheritance differently for pwsh.exe vs powershell.exe:

• powershell.exe (native Windows console host): Child processes inherit
  DC's stdio pipes correctly. stdout flows back through Node.js to DC.
• pwsh.exe (.NET 8 app): Child processes appear to get a new console
  allocation instead of inheriting pipes. stdout goes to the visible console
  window, not back to DC.

This may relate to:

• .NET 8 runtime allocating its own console via AllocConsole()
• Differences in how CreateProcess handles STARTUPINFO for .NET vs native
  executables
• Node.js spawn not setting CREATE_NO_WINDOW or DETACHED_PROCESS flags
  appropriately for .NET-based shells

Workaround

Using powershell.exe (5.1) as defaultShell. This has its own issues
(UTF-8 BOM injection in pipes, UTF-16LE encoding in redirects) but stdout
capture works reliably for all external executables.

Suggested Fix

The getShellSpawnArgs() function in terminal-manager.js may need
platform-specific spawn options for pwsh.exe on Windows, such as:

• Explicit windowsHide: true in spawn options
• CREATE_NO_WINDOW process creation flag
• Different stdio configuration for .NET-based shells