The stale-dashboard sweep at the end of hermes update snapshots each killed
backend's HERMES_HOME (_hermes_home_for_pid) but only used it as the per-profile
dedupe key. _respawn_dashboard_processes replays the argv with no env=, so a
backend belonging to a second install (e.g. a launchd KeepAlive sidecar) came
back running on the updating install's default home and stole the sidecar's
fixed port: the supervisor crash-looped on EADDRINUSE and clients on that port
silently talked to the wrong backend.
Drop such candidates in _filter_dashboard_respawn_candidates: a backend whose
captured HERMES_HOME differs from the updater's own get_hermes_home() is not
replayed at all — its own supervisor/user owns its lifecycle. Homes are
normalized the same way _profile_key_for_respawn normalizes home: keys, so
symlinked roots compare equal. An unreadable home (None) stays eligible,
keeping the pre-fix fail-open behaviour.
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