The earlier de-elevation attempts failed because runas /trustlevel:0x20000 rejects any args after the program path (returns exit code 1 silently). Switch the relaunch loop-guard from --relaunched CLI arg to TEAMSISO_RELAUNCHED env var, which runas inherits and propagates cleanly. Also: always demote when elevated regardless of parent (the parent==explorer heuristic was too narrow; the runas demotion is cheap enough to do unconditionally), and add a StartupTrace fallback log at %LOCALAPPDATA%\\TeamsISO\\startup-trace.log that captures every checkpoint in OnStartup so future launch failures can be diagnosed without Serilog being up.
Verified end-to-end: elevated parent (PID 47536, isAdmin=True) -> spawns runas -> medium-integrity child (PID 51228, isAdmin=False) -> NDI discovery succeeds (vm.Participants.Count=2 at +5s). The TryDeElevateAndExit now returns bool so spawn failures fall through to normal startup instead of leaving the process in a zombie state.
Opt-out: --keep-elevation CLI arg bypasses the demotion.
