fix: QThread crash on iPod connect and device detection — proper wait() lifecycle

Root cause: QThread C++ destructor ran while underlying OS thread was
still terminating. The pattern of checking isRunning() and using
short timeouts (wait(3000/5000)) left a window where the Python
reference was dropped and Shiboken destroyed the C++ object before
the thread fully exited.

Fixes:
- Remove all self.finished.connect(self.deleteLater) — unsafe,
  deleteLater from within run() or from worker thread races with
  thread termination
- _cleanup_worker: always call wait() (no timeout) before nulling
  the Python reference — guarantees OS thread is fully dead
- Add _is_worker_running() helper with try/except RuntimeError
  guard to safely check stale C++ objects
- DeviceMonitor._poll/stop/wait: use wait() with no timeout
- closeEvent: guard isRunning() with try/except RuntimeError

src/app.py

@@ -66,7 +66,6 @@ class MainWindow(QMainWindow):
         self.library_tab._scan_library()
         self._resume_playback_if_saved()
         self._restore_library_state()
-        self.ipod_tab._on_refresh_devices_clicked()
         self._start_device_monitor()
 
     def _setup_player(self):
@@ -427,7 +426,17 @@ class MainWindow(QMainWindow):
     def closeEvent(self, event):
         if self.device_monitor:
             self.device_monitor.stop()
+            self.ipod_tab.stop_monitoring(self.device_monitor)
+        for tab in (self.ipod_tab, self.library_tab):
+            if hasattr(tab, 'worker_thread') and tab.worker_thread:
+                try:
+                    if tab.worker_thread.isRunning():
+                        tab.worker_thread.stop()
+                except RuntimeError:
+                    tab.worker_thread = None
         self._save_settings()
+        from PyQt6.QtWidgets import QApplication
+        QApplication.processEvents()
         event.accept()
 
 

src/device_monitor.py

@@ -11,6 +11,9 @@ logger = logging.getLogger(__name__)
 class _DetectWorker(QThread):
     finished = pyqtSignal(object)
 
+    def __init__(self, parent=None):
+        super().__init__(parent)
+
     def run(self):
         try:
             devices = IPodDevice().detect_devices()
@@ -38,19 +41,29 @@ class DeviceMonitor(QObject):
 
     def stop(self):
         self.timer.stop()
-        if self._poll_worker and self._poll_worker.isRunning():
+        if self._poll_worker:
             self._poll_worker.quit()
-            self._poll_worker.wait(3000)
+            self._poll_worker.wait()
+            self._poll_worker = None
         self._device_ids.clear()
 
     def _poll(self):
-        if self._poll_worker and self._poll_worker.isRunning():
+        if self._poll_worker:
+            try:
+                if self._poll_worker.isRunning():
                     return
-        self._poll_worker = _DetectWorker()
+            except RuntimeError:
-        self._poll_worker.finished.connect(self._on_devices_detected)
+                self._poll_worker = None
-        self._poll_worker.start()
+        worker = _DetectWorker()
+        worker.finished.connect(self._on_devices_detected)
+        worker.start()
+        self._poll_worker = worker
 
     def _on_devices_detected(self, devices):
+        if self._poll_worker:
+            self._poll_worker.quit()
+            self._poll_worker.wait()
+            self._poll_worker = None
         current_ids = {d["id"] for d in devices}
         if current_ids != self._device_ids:
             self._device_ids = current_ids

src/ui/ipod_tab.py

@@ -107,7 +107,7 @@ class iPodTab(QWidget):
         layout.addWidget(self.delete_status)
 
     def _on_refresh_devices_clicked(self):
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             return
 
         self.device_combo.clear()
@@ -122,6 +122,8 @@ class iPodTab(QWidget):
         self.device_info_label.setText(status)
 
     def _on_device_detection_finished(self, success, message, result):
+        self._cleanup_worker()
+
         if success:
             self.ipod_devices = result
             self.device_combo.clear()
@@ -140,8 +142,6 @@ class iPodTab(QWidget):
         else:
             self._set_device_not_found()
 
-        self._cleanup_worker()
-
     def _start_mount_and_load(self, device: dict, mount_point=None, already_mounted=False):
         self.device_status_label.setText("Mounting and loading tracks...")
         self.mount_button.setEnabled(False)
@@ -320,11 +320,12 @@ class iPodTab(QWidget):
         if reply != QMessageBox.StandardButton.Yes:
             return
 
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             QMessageBox.information(self, "Info", "Please wait for the current task to finish")
             return
 
         pids = []
+
         for item in selected:
             track_data = item.data(Qt.ItemDataRole.UserRole)
             if track_data and "pid" in track_data:
@@ -391,7 +392,7 @@ class iPodTab(QWidget):
             QMessageBox.warning(self, "Error", "No valid track files found on device")
             return
 
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             QMessageBox.information(self, "Info", "Please wait for the current task to finish")
             return
 
@@ -470,7 +471,7 @@ class iPodTab(QWidget):
             QMessageBox.warning(self, "Error", "No iPod device mounted.")
             return
 
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             QMessageBox.information(self, "Info", "Please wait for the current task to finish")
             return
 
@@ -506,12 +507,20 @@ class iPodTab(QWidget):
             pass
 
     def _on_auto_state_changed(self, devices):
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             return
         self._on_device_detection_finished(True, f"Found {len(devices)} devices", devices)
 
     def _cleanup_worker(self):
         if self.worker_thread:
-            self.worker_thread.wait(3000)
+            self.worker_thread.quit()
-            self.worker_thread.deleteLater()
+            self.worker_thread.wait()
             self.worker_thread = None
+
+    def _is_worker_running(self):
+        if self.worker_thread:
+            try:
+                return self.worker_thread.isRunning()
+            except RuntimeError:
+                self.worker_thread = None
+        return False

src/ui/library_tab.py

@@ -957,7 +957,7 @@ class LibraryTab(QWidget):
             )
             return
 
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             QMessageBox.information(self, "Info", "Please wait for the current task to finish")
             return
 
@@ -1025,7 +1025,7 @@ class LibraryTab(QWidget):
             QMessageBox.warning(self, "Error", "No iPod device mounted. Go to iPod tab and mount first.")
             return
 
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             QMessageBox.information(self, "Info", "Please wait for the current task to finish")
             return
 
@@ -1070,7 +1070,7 @@ class LibraryTab(QWidget):
             QMessageBox.warning(self, "Error", "No iPod device mounted.")
             return
 
-        if self.worker_thread and self.worker_thread.isRunning():
+        if self._is_worker_running():
             QMessageBox.information(self, "Info", "Please wait for the current task to finish")
             return
 
@@ -1140,10 +1140,18 @@ class LibraryTab(QWidget):
 
     def _cleanup_worker(self):
         if self.worker_thread:
-            self.worker_thread.wait(3000)
+            self.worker_thread.quit()
-            self.worker_thread.deleteLater()
+            self.worker_thread.wait()
             self.worker_thread = None
 
+    def _is_worker_running(self):
+        if self.worker_thread:
+            try:
+                return self.worker_thread.isRunning()
+            except RuntimeError:
+                self.worker_thread = None
+        return False
+
     def on_device_mounted(self, mount_point: str):
         self._current_mount_point = mount_point
         self.library_progress.setVisible(True)

src/worker.py

@@ -27,8 +27,8 @@ class WorkerThread(QThread):
     progress_signal = pyqtSignal(int, str)
     finished_signal = pyqtSignal(bool, str, object)
 
-    def __init__(self, task_type: str, **kwargs):
+    def __init__(self, task_type: str, parent=None, **kwargs):
-        super().__init__()
+        super().__init__(parent)
         self.task_type = task_type
         self.kwargs = kwargs
         self.is_running = True