diff --git a/tui/src/birdcage_tui/app.py b/tui/src/birdcage_tui/app.py
index c7990d1..87f03f8 100644
--- a/tui/src/birdcage_tui/app.py
+++ b/tui/src/birdcage_tui/app.py
@@ -6,6 +6,7 @@ device status bar, and five swappable screen panels.
 
 import argparse
 import logging
+import threading
 
 from textual.app import App, ComposeResult
 from textual.binding import Binding
@@ -52,6 +53,7 @@ class BirdcageApp(App):
     firmware_name: str = "g2"
     skip_init: bool = False
     device: object = None
+    shutdown_event: threading.Event = threading.Event()
 
     @property
     def SUB_TITLE(self) -> str:  # noqa: N802
@@ -130,13 +132,8 @@ class BirdcageApp(App):
             screen.on_show()
 
     def on_unmount(self) -> None:
-        """Stop all polling threads and disconnect the device on shutdown."""
-        for mode_key in MODES:
-            screen = self.query_one(f"#{mode_key}")
-            if hasattr(screen, "_polling"):
-                screen._polling = False
-            if hasattr(screen, "_monitoring"):
-                screen._monitoring = False
+        """Signal all worker threads to exit and disconnect the device."""
+        self.shutdown_event.set()
         if self.device and hasattr(self.device, "disconnect"):
             self.device.disconnect()
 
@@ -173,4 +170,11 @@ def main() -> None:
     app.serial_port = args.port
     app.firmware_name = args.firmware
     app.skip_init = args.skip_init
-    app.run()
+    try:
+        app.run()
+    except KeyboardInterrupt:
+        pass
+    finally:
+        app.shutdown_event.set()
+        if app.device and hasattr(app.device, "disconnect"):
+            app.device.disconnect()
diff --git a/tui/src/birdcage_tui/screens/position.py b/tui/src/birdcage_tui/screens/position.py
index 388b3c6..ca197b8 100644
--- a/tui/src/birdcage_tui/screens/position.py
+++ b/tui/src/birdcage_tui/screens/position.py
@@ -6,7 +6,6 @@ and AZ/EL sparklines. Bottom row provides manual move controls.
 """
 
 import logging
-import time
 
 from textual import work
 from textual.app import ComposeResult
@@ -98,9 +97,10 @@ class PositionScreen(Container):
     @work(thread=True, exclusive=True, group="position-poll")
     def _do_position_poll(self) -> None:
         """Poll device at ~2 Hz for position and step data."""
-        while self._polling:
+        shutdown = self.app.shutdown_event
+        while self._polling and not shutdown.is_set():
             if self._device is None:
-                time.sleep(0.5)
+                shutdown.wait(0.5)
                 continue
 
             try:
@@ -135,7 +135,7 @@ class PositionScreen(Container):
             except Exception:
                 log.debug("Torque poll failed", exc_info=True)
 
-            time.sleep(0.5)
+            shutdown.wait(0.5)
 
     # ------------------------------------------------------------------
     # Thread-safe widget update callbacks
diff --git a/tui/src/birdcage_tui/screens/scan.py b/tui/src/birdcage_tui/screens/scan.py
index a194196..7be6fab 100644
--- a/tui/src/birdcage_tui/screens/scan.py
+++ b/tui/src/birdcage_tui/screens/scan.py
@@ -7,7 +7,6 @@ raw (az, el, rssi) data for offline analysis.
 
 import csv
 import logging
-import time
 from pathlib import Path
 
 from textual import work
@@ -98,6 +97,7 @@ class ScanScreen(Container):
     def _do_scan(self) -> None:
         """Execute the AZ/EL grid scan in a background thread."""
         worker = get_current_worker()
+        shutdown = self.app.shutdown_event
         device = self._device
         if device is None:
             return
@@ -146,7 +146,7 @@ class ScanScreen(Container):
 
         for _el_idx, el_val in enumerate(el_values):
             for _az_idx, az_val in enumerate(az_values):
-                if not self._scanning or worker.is_cancelled:
+                if not self._scanning or worker.is_cancelled or shutdown.is_set():
                     self.app.call_from_thread(self._set_status, "Scan stopped")
                     return
 
@@ -160,7 +160,7 @@ class ScanScreen(Container):
                     continue
 
                 # Settle time -- let the motor stop and vibrations damp.
-                time.sleep(0.3)
+                shutdown.wait(0.3)
 
                 # Read signal.
                 try:
diff --git a/tui/src/birdcage_tui/screens/signal.py b/tui/src/birdcage_tui/screens/signal.py
index 9b7c7e9..9a5ac27 100644
--- a/tui/src/birdcage_tui/screens/signal.py
+++ b/tui/src/birdcage_tui/screens/signal.py
@@ -7,7 +7,6 @@ sparklines for DVB and ADC RSSI, peak tracking, and LNA toggle.
 
 import logging
 import re
-import time
 
 from textual import work
 from textual.app import ComposeResult
@@ -82,9 +81,10 @@ class SignalScreen(Container):
     @work(thread=True, exclusive=True, group="signal-poll")
     def _do_signal_poll(self) -> None:
         """Poll RSSI at the configured rate while monitoring is active."""
-        while self._monitoring:
+        shutdown = self.app.shutdown_event
+        while self._monitoring and not shutdown.is_set():
             if self._device is None:
-                time.sleep(0.5)
+                shutdown.wait(0.5)
                 continue
 
             # Read config from inputs (safe defaults on parse failure).
@@ -141,7 +141,7 @@ class SignalScreen(Container):
             except Exception:
                 log.debug("Lock status poll failed", exc_info=True)
 
-            time.sleep(1.0 / rate)
+            shutdown.wait(1.0 / rate)
 
     # ------------------------------------------------------------------
     # Thread-safe widget update callbacks