One external binary this platform's spawn paths must load, and whether this host actually holds it. ProcessKit shells out to a helper only where the OS offers no in-process equivalent — arming `PR_SET_PDEATHSIG` inside the child, establishing a controlling terminal, running a `.cmd` shim. A missing helper is never worked around silently: the affected verb fails with a typed `ProcessError` naming the helper. This entry is that same fact, available *before* the spawn. The POSIX security helpers are resolved only from a fixed list of trusted system directories and never from `PATH`, so a helper present on `PATH` alone is reported missing here — deliberately, because the spawn refuses it too (a `PATH`-hijackable binary would run with the caller's full privileges before any drop). See the hardening guide.