🪟 The Windows Service Black Window Mystery — NSSM + .cmd = A Console That Won't Close

The Problem

You're using NSSM to run a script as a Windows service. Every time the service starts, a black console window appears. You close it — the service stops.

This happens specifically when NSSM runs a .cmd or .bat file directly.

Why It Happens

NSSM invokes cmd.exe as the parent process for .cmd files. cmd.exe creates a console window by default. Closing it terminates the process.

The Fix: Run the Executable Directly

Point NSSM at the actual executable, not the .cmd wrapper:

# Wrong:  NSSM Application = C:\scripts\start.cmd
# Right:  NSSM Application = C:\Python311\python.exe
#         NSSM Arguments   = C:\scripts\your_script.py

Alternative: .vbs Wrapper

If you must use a .cmd script, wrap it in VBScript:

CreateObject("WScript.Shell").Run "cmd /c C:\scripts\start.cmd", 0, False

Point NSSM at wscript.exe with the .vbs file as the argument. The 0 hides the window.