implement parent monitoring thread

fixes #7

src/jsi/cli.py

@@ -53,6 +53,7 @@
 import signal
 import sys
 import threading
+import time
 from functools import partial
 
 from jsi.config.loader import Config, find_available_solvers, load_definitions
@@ -134,6 +135,38 @@ def cleanup():
     atexit.register(cleanup)
 
 
+def monitor_parent():
+    """
+    Monitor the parent process and exit if it dies or changes.
+
+    Caveats:
+    - only works on POSIX systems
+    - only works if called early enough (before the original parent process exits)
+    """
+
+    parent_pid = os.getppid()
+
+    def check_parent():
+        while True:
+            try:
+                current_ppid = os.getppid()
+
+                # if parent PID changed (original parent died), we exit
+                if current_ppid != parent_pid or current_ppid == 1:
+                    stderr.print("parent process died, exiting...")
+                    os.kill(os.getpid(), signal.SIGTERM)
+                    break
+                time.sleep(1)  # check every second
+            except ProcessLookupError:
+                # if we can't check parent PID, assume parent died
+                os.kill(os.getpid(), signal.SIGTERM)
+                break
+
+    # Start monitoring in background thread
+    monitor_thread = threading.Thread(target=check_parent, daemon=True)
+    monitor_thread.start()
+
+
 class BadParameterError(Exception):
     pass
 
@@ -229,6 +262,9 @@ def main(args: list[str] | None = None) -> int:
     global stdout
     global stderr
 
+    # kick off the parent monitor in the background as early as possible
+    monitor_parent()
+
     if args is None:
         args = sys.argv[1:]
 

src/jsi/server.py

@@ -206,9 +206,11 @@ def sync_solve(self, file: str) -> str:
 
         listener = ResultListener()
         controller = ProcessController(
-            task, commands, self.config,
+            task,
+            commands,
+            self.config,
             start_callback=start_logger,
-            exit_callback=listener.exit_callback
+            exit_callback=listener.exit_callback,
         )
         controller.start()