When shell=True was removed for security, the command was parsed with
shlex.split(posix=False) on Windows, which keeps the quote characters inside
the tokens — so a quoted path like "C:\Program Files\app.exe" became an argv[0]
containing literal quotes and CreateProcess couldn't find it, so app macros
silently did nothing.
Fix: on Windows pass the command string to Popen (shell=False) and let
CreateProcess parse it (handles quoted paths, still no shell/metacharacter
chaining); on POSIX keep shlex.split. Verified a real launch works and shell
redirection stays blocked.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
shadowdao