Client: relaunch MasterTech while RemoteExec is armed - #366

Summary

While RemoteExec is armed, MasterTech now comes back by itself when it dies or Windows restarts, so an overnight remote job doesn't stall until someone walks over to the machine.

• Arming RemoteExec registers a MastertechWatchdog scheduled task for the logged-on user, at the highest run level. It has two triggers:
  • a logon trigger;
  • a trigger that repeats every 5 minutes.
• Both triggers expire one hour after the lease ends, and the expired task deletes itself.
• The task starts MasterTech.exe --watchdog. A --watchdog launch exits at once when the Local\MasterTech.Instance mutex shows an instance is already running. Every GUI and terminal instance opens that mutex at startup; --mcp-stdio does not.
• These remove the task:
  • disarming RemoteExec;
  • closing MasterTech normally.
• A close while Windows is shutting down keeps the task (SM_SHUTTINGDOWN), so MasterTech returns after a reboot that MasterTech didn't start itself.
• The existing one-shot reboot relaunch (MastertechAutoRestart) now passes --watchdog too, so the two tasks never start a second copy.
• Task settings:
  • IgnoreNew, so a running copy the task started blocks repeat launches;
  • no execution time limit (the default 72 h limit would end a long-running MasterTech);
  • starts when available, and runs on battery.
• The remote_exec_arm tool description now tells agents that the relaunched client comes back disarmed and needs a re-arm.
• MTECH_NO_WATCHDOG=1 skips registration.

Why

A QC machine's MasterTech died mid-install overnight. Nothing could relaunch it until a technician came in, so the rest of the QC sat idle for the night. Webroot kills (see the vssadmin rule) end the session the same way.

Testing

• Unit tests for the generated PowerShell:
  • flag and terminal-mode arguments;
  • expiry and self-delete;
  • no time limit, IgnoreNew, highest run level;
  • quote escaping and the minimum window;
  • --watchdog parsing.
• Probes on Windows 11 26200 with throwaway tasks, through PowerShell 5.1 the way MasterTech runs it:
  • the generated script registers;
  • EndBoundary keeps its UTC offset, DeleteExpiredTaskAfter is PT0S and ExecutionTimeLimit is PT0S;
  • a second start under IgnoreNew starts no new instance;
  • re-registering with -Force and deleting with schtasks /delete both leave the running instance alive.
• cargo clippy -p MasterTech --no-deps --bin MasterTech --tests: nothing new.

Clients need a release to pick this up.

🤖 Generated with Claude Code