diff --git a/bec_widgets/utils/bec_widget.py b/bec_widgets/utils/bec_widget.py
index 7235f666..39be8219 100644
--- a/bec_widgets/utils/bec_widget.py
+++ b/bec_widgets/utils/bec_widget.py
@@ -1,3 +1,4 @@
+from qtpy.QtCore import Slot
 from qtpy.QtWidgets import QApplication, QWidget
 
 from bec_widgets.utils.bec_connector import BECConnector, ConnectionConfig
@@ -11,7 +12,13 @@ class BECWidget(BECConnector):
     # from fonts.google.com/icons. Override this in subclasses to set the icon name.
     ICON_NAME = "widgets"
 
-    def __init__(self, client=None, config: ConnectionConfig = None, gui_id: str = None):
+    def __init__(
+        self,
+        client=None,
+        config: ConnectionConfig = None,
+        gui_id: str = None,
+        theme_update: bool = False,
+    ):
         if not isinstance(self, QWidget):
             raise RuntimeError(f"{repr(self)} is not a subclass of QWidget")
         super().__init__(client, config, gui_id)
@@ -19,7 +26,36 @@ class BECWidget(BECConnector):
         # Set the theme to auto if it is not set yet
         app = QApplication.instance()
         if not hasattr(app, "theme"):
-            set_theme("dark")
+            set_theme("auto")
+
+        if theme_update:
+            self._connect_to_theme_change()
+
+    def _connect_to_theme_change(self):
+        """Connect to the theme change signal."""
+        qapp = QApplication.instance()
+        if hasattr(qapp, "theme_signal"):
+            qapp.theme_signal.theme_updated.connect(self._update_theme)
+
+    @Slot(str)
+    def _update_theme(self, theme: str):
+        """Update the theme."""
+        if theme is None:
+            qapp = QApplication.instance()
+            if hasattr(qapp, "theme"):
+                theme = qapp.theme["theme"]
+            else:
+                theme = "dark"
+        self.apply_theme(theme)
+
+    @Slot(str)
+    def apply_theme(self, theme: str):
+        """
+        Apply the theme to the plot widget.
+
+        Args:
+            theme(str, optional): The theme to be applied.
+        """
 
     def cleanup(self):
         """Cleanup the widget."""
diff --git a/bec_widgets/utils/colors.py b/bec_widgets/utils/colors.py
index de98ccba..a94e100e 100644
--- a/bec_widgets/utils/colors.py
+++ b/bec_widgets/utils/colors.py
@@ -19,6 +19,17 @@ def get_theme_palette():
     return bec_qthemes.load_palette(theme)
 
 
+def _theme_update_callback():
+    """
+    Internal callback function to update the theme based on the system theme.
+    """
+    app = QApplication.instance()
+    # pylint: disable=protected-access
+    app.theme["theme"] = app.os_listener._theme.lower()
+    app.theme_signal.theme_updated.emit(app.theme["theme"])
+    apply_theme(app.os_listener._theme.lower())
+
+
 def set_theme(theme: Literal["dark", "light", "auto"]):
     """
     Set the theme for the application.
@@ -27,23 +38,17 @@ def set_theme(theme: Literal["dark", "light", "auto"]):
         theme (Literal["dark", "light", "auto"]): The theme to set. "auto" will automatically switch between dark and light themes based on the system theme.
     """
     app = QApplication.instance()
-    bec_qthemes.setup_theme(theme)
-    pg.setConfigOption("background", "w" if app.theme["theme"] == "light" else "k")
+    bec_qthemes.setup_theme(theme, install_event_filter=False)
+
     app.theme_signal.theme_updated.emit(theme)
     apply_theme(theme)
 
-    # pylint: disable=protected-access
     if theme != "auto":
         return
 
-    def callback():
-        app.theme["theme"] = listener._theme.lower()
-        app.theme_signal.theme_updated.emit(app.theme["theme"])
-        apply_theme(listener._theme.lower())
-
-    listener = OSThemeSwitchListener(callback)
-
-    app.installEventFilter(listener)
+    if not hasattr(app, "os_listener") or app.os_listener is None:
+        app.os_listener = OSThemeSwitchListener(_theme_update_callback)
+        app.installEventFilter(app.os_listener)
 
 
 def apply_theme(theme: Literal["dark", "light"]):
@@ -55,21 +60,12 @@ def apply_theme(theme: Literal["dark", "light"]):
     children = itertools.chain.from_iterable(
         top.findChildren(pg.GraphicsLayoutWidget) for top in app.topLevelWidgets()
     )
-    pg.setConfigOptions(foreground="d" if theme == "dark" else "k")
+    pg.setConfigOptions(
+        foreground="d" if theme == "dark" else "k", background="k" if theme == "dark" else "w"
+    )
     for pg_widget in children:
         pg_widget.setBackground("k" if theme == "dark" else "w")
 
-    dark_mode_buttons = [
-        button
-        for button in app.topLevelWidgets()
-        if hasattr(button, "dark_mode_enabled")
-        and hasattr(button, "mode_button")
-        and isinstance(button.mode_button, (QPushButton, QToolButton))
-    ]
-
-    for button in dark_mode_buttons:
-        button.dark_mode_enabled = theme == "dark"
-        button.update_mode_button()
     # now define stylesheet according to theme and apply it
     style = bec_qthemes.load_stylesheet(theme)
     app.setStyleSheet(style)
diff --git a/bec_widgets/widgets/dark_mode_button/dark_mode_button.py b/bec_widgets/widgets/dark_mode_button/dark_mode_button.py
index ca9cead6..40601248 100644
--- a/bec_widgets/widgets/dark_mode_button/dark_mode_button.py
+++ b/bec_widgets/widgets/dark_mode_button/dark_mode_button.py
@@ -18,7 +18,7 @@ class DarkModeButton(BECWidget, QWidget):
         gui_id: str | None = None,
         toolbar: bool = False,
     ) -> None:
-        super().__init__(client=client, gui_id=gui_id)
+        super().__init__(client=client, gui_id=gui_id, theme_update=True)
         QWidget.__init__(self, parent)
 
         self._dark_mode_enabled = False
@@ -39,6 +39,17 @@ class DarkModeButton(BECWidget, QWidget):
         self.setLayout(self.layout)
         self.setFixedSize(40, 40)
 
+    @Slot(str)
+    def apply_theme(self, theme: str):
+        """
+        Apply the theme to the widget.
+
+        Args:
+            theme(str, optional): The theme to be applied.
+        """
+        self.dark_mode_enabled = theme == "dark"
+        self.update_mode_button()
+
     def _get_qapp_dark_mode_state(self) -> bool:
         """
         Get the dark mode state from the QApplication.
diff --git a/bec_widgets/widgets/figure/plots/plot_base.py b/bec_widgets/widgets/figure/plots/plot_base.py
index 7410b366..55d43284 100644
--- a/bec_widgets/widgets/figure/plots/plot_base.py
+++ b/bec_widgets/widgets/figure/plots/plot_base.py
@@ -99,30 +99,32 @@ class BECPlotBase(BECConnector, pg.GraphicsLayout):
 
         self.add_legend()
         self.crosshair = None
-        self.connect_to_theme_change()
-        self.apply_theme()
+        self._connect_to_theme_change()
 
-    def connect_to_theme_change(self):
+    def _connect_to_theme_change(self):
         """Connect to the theme change signal."""
         qapp = QApplication.instance()
         if hasattr(qapp, "theme_signal"):
-            qapp.theme_signal.theme_updated.connect(self.apply_theme)
+            qapp.theme_signal.theme_updated.connect(self._update_theme)
 
     @Slot(str)
-    @Slot()
-    def apply_theme(self, theme: str | None = None):
-        """
-        Apply the theme to the plot widget.
-
-        Args:
-            theme(str, optional): The theme to be applied.
-        """
+    def _update_theme(self, theme: str):
+        """Update the theme."""
         if theme is None:
             qapp = QApplication.instance()
             if hasattr(qapp, "theme"):
                 theme = qapp.theme["theme"]
             else:
                 theme = "dark"
+        self.apply_theme(theme)
+
+    def apply_theme(self, theme: str):
+        """
+        Apply the theme to the plot widget.
+
+        Args:
+            theme(str, optional): The theme to be applied.
+        """
         palette = bec_qthemes.load_palette(theme)
         text_pen = pg.mkPen(color=palette.text().color())
 
diff --git a/tests/unit_tests/conftest.py b/tests/unit_tests/conftest.py
index 2ba47d43..e91b90f6 100644
--- a/tests/unit_tests/conftest.py
+++ b/tests/unit_tests/conftest.py
@@ -14,6 +14,8 @@ def qapplication(qtbot):  # pylint: disable=unused-argument
     qapp = QApplication.instance()
     # qapp.quit()
     qapp.processEvents()
+    if hasattr(qapp, "os_listener") and qapp.os_listener:
+        qapp.removeEventFilter(qapp.os_listener)
     try:
         qtbot.waitUntil(lambda: qapp.topLevelWidgets() == [])
     except QtBotTimeoutError as exc:
diff --git a/tests/unit_tests/test_dark_mode_button.py b/tests/unit_tests/test_dark_mode_button.py
index 36f0f1ac..6114d648 100644
--- a/tests/unit_tests/test_dark_mode_button.py
+++ b/tests/unit_tests/test_dark_mode_button.py
@@ -2,6 +2,7 @@ from unittest import mock
 
 import pytest
 from qtpy.QtCore import Qt
+from qtpy.QtWidgets import QApplication
 
 from bec_widgets.utils.colors import set_theme
 from bec_widgets.widgets.dark_mode_button.dark_mode_button import DarkModeButton
@@ -70,3 +71,16 @@ def test_dark_mode_button_changes_theme(dark_mode_button):
 
         dark_mode_button.toggle_dark_mode()
         mocked_set_theme.assert_called_with("light")
+
+
+def test_dark_mode_button_changes_on_os_theme_change(qtbot, dark_mode_button):
+    """
+    Test that the dark mode button changes the theme correctly when the OS theme changes.
+    """
+    qapp = QApplication.instance()
+    assert dark_mode_button.dark_mode_enabled is False
+    assert dark_mode_button.mode_button.toolTip() == "Set Dark Mode"
+    qapp.theme_signal.theme_updated.emit("dark")
+    qtbot.wait(100)
+    assert dark_mode_button.dark_mode_enabled is True
+    assert dark_mode_button.mode_button.toolTip() == "Set Light Mode"
diff --git a/tests/unit_tests/test_vscode_widget.py b/tests/unit_tests/test_vscode_widget.py
index c8d07e1b..bf81a02c 100644
--- a/tests/unit_tests/test_vscode_widget.py
+++ b/tests/unit_tests/test_vscode_widget.py
@@ -61,7 +61,7 @@ def test_vscode_cleanup(qtbot, patched_vscode_process):
     vscode_patched, mock_killpg = patched_vscode_process
     vscode_patched.process.pid = 123
     vscode_patched.process.poll.return_value = None
-    vscode_patched.cleanup()
+    vscode_patched.cleanup_vscode()
     mock_killpg.assert_called_once_with(123, 15)
     vscode_patched.process.wait.assert_called_once()
 
@@ -70,6 +70,6 @@ def test_close_event_on_terminated_code(qtbot, patched_vscode_process):
     vscode_patched, mock_killpg = patched_vscode_process
     vscode_patched.process.pid = 123
     vscode_patched.process.poll.return_value = 0
-    vscode_patched.cleanup()
+    vscode_patched.cleanup_vscode()
     mock_killpg.assert_not_called()
     vscode_patched.process.wait.assert_not_called()
diff --git a/tests/unit_tests/test_waveform_widget.py b/tests/unit_tests/test_waveform_widget.py
index 19a71849..abe31e8a 100644
--- a/tests/unit_tests/test_waveform_widget.py
+++ b/tests/unit_tests/test_waveform_widget.py
@@ -2,8 +2,11 @@ from unittest.mock import MagicMock, patch
 
 import pyqtgraph as pg
 import pytest
+from qtpy.QtGui import QColor
+from qtpy.QtWidgets import QApplication
 
 from bec_widgets.qt_utils.settings_dialog import SettingsDialog
+from bec_widgets.utils.colors import apply_theme, get_theme_palette, set_theme
 from bec_widgets.widgets.figure.plots.axis_settings import AxisSettings
 from bec_widgets.widgets.waveform.waveform_popups.curve_dialog.curve_dialog import CurveSettings
 from bec_widgets.widgets.waveform.waveform_widget import BECWaveformWidget
@@ -460,3 +463,42 @@ def test_axis_dialog_set_properties(qtbot, waveform_widget):
     assert waveform_widget._config_dict["axis"]["y_scale"] == "linear"
     assert waveform_widget._config_dict["axis"]["x_lim"] == (5, 15)
     assert waveform_widget._config_dict["axis"]["y_lim"] == (5, 15)
+
+
+def test_waveform_widget_theme_update(qtbot, waveform_widget):
+    """Test theme update for waveform widget."""
+    qapp = QApplication.instance()
+
+    # Set the theme directly; equivalent to clicking the dark mode button
+    # The background color should be black and the axis color should be white
+    set_theme("dark")
+    palette = get_theme_palette()
+    waveform_color_dark = waveform_widget.waveform.plot_item.getAxis("left").pen().color()
+    bg_color = waveform_widget.fig.backgroundBrush().color()
+    assert bg_color == QColor("black")
+    assert waveform_color_dark == palette.text().color()
+
+    # Set the theme to light; equivalent to clicking the light mode button
+    # The background color should be white and the axis color should be black
+    set_theme("light")
+    palette = get_theme_palette()
+    waveform_color_light = waveform_widget.waveform.plot_item.getAxis("left").pen().color()
+    bg_color = waveform_widget.fig.backgroundBrush().color()
+    assert bg_color == QColor("white")
+    assert waveform_color_light == palette.text().color()
+
+    assert waveform_color_dark != waveform_color_light
+
+    # Set the theme to auto; equivalent starting the application with no theme set
+    set_theme("auto")
+    # Simulate that the OS theme changes to dark
+    qapp.theme_signal.theme_updated.emit("dark")
+    apply_theme("dark")
+
+    # The background color should be black and the axis color should be white
+    # As we don't have access to the listener here, we can't test the palette change. Instead,
+    # we compare the waveform color to the dark theme color
+    waveform_color = waveform_widget.waveform.plot_item.getAxis("left").pen().color()
+    bg_color = waveform_widget.fig.backgroundBrush().color()
+    assert bg_color == QColor("black")
+    assert waveform_color == waveform_color_dark