Repo scanners (check_subprocess_stdin, check-windows-footguns --all) flagged 21 sites where the r3 single-line collapses lost stdin=DEVNULL, encoding='utf-8'/errors='replace', the '# windows-footgun: ok' same-line marker, or the getattr(os, 'geteuid') gate. Each guard is restored at the call site (real portability/hang fixes, not suppressions).