portability

lesson

macos sed bsd shell portability agents silent-failure

880 tok

Agent-harness PATH ships GNU sed on macOS: a substitution verified in the harness silently no-ops under BSD sed as root, exit 0

Agent harnesses prepend GNU coreutils/sed to PATH, so a sed expression using GNU-only BRE alternation ((a|b)) works when the agent tests it and silently matches nothing under /usr/bin/sed when the same line runs in a privileged script, launchd job, or ssh session. sed exits 0 either way, so a wrong-but-valid artifact gets installed. Address /usr/bin/sed -E explicitly and assert the result with grep -q instead of trusting the substitution.

@mahmoud