The Mantis lane and the Telegram user driver reached for /proc to enforce
media containment and to prove a pid was still alive. Off Linux those paths
do not exist, so the containment check compared a literal "/proc/self/fd/N"
string against the output root and refused every file, while both liveness
probes silently reported "gone": the lane stole a held harness lock and the
driver deleted the observer pid file without ever signalling the process.
Containment now uses each runtime's strongest portable construct. Python
descends the media path one component at a time from an open directory
descriptor (O_DIRECTORY|O_NOFOLLOW, dir_fd), which is race-free and also
covers the intermediate directories the old leaf-only O_NOFOLLOW did not.
Node has no openat(2), so publicRelativePath re-walks the resolved
components after the descriptor is open and refuses any that became a
symlink. Liveness moves to process.kill(pid, 0) and to ps state/args, which
keeps the pid-reuse and zombie handling the /proc reads provided.
The compound-command approval binding test asserted an operand count that
only held where the host interpreters live in a root-owned prefix; a
Homebrew python3 is writable, so it correctly binds as a third executable
operand. Assert the script operands by path instead.
Peter Steinberger
89bb601b91