diff --git a/src/optiverse/core/raytracing_math.py b/src/optiverse/core/raytracing_math.py
index eb3acae3..6601edf9 100644
--- a/src/optiverse/core/raytracing_math.py
+++ b/src/optiverse/core/raytracing_math.py
@@ -12,8 +12,12 @@
 
     NUMBA_AVAILABLE = True
 except ImportError:
-    # Fallback: no-op decorator if numba isn't available
-    def jit(*args, **kwargs):
+    # Fallback: no-op decorator if numba isn't available. mypy flags the
+    # redefinition differently depending on whether numba is importable in the
+    # analysis environment (no-redef when it is, misc when it isn't), so both
+    # codes are suppressed for cross-platform CI. warn_unused_ignores is off,
+    # so the code that doesn't apply on a given platform is harmless.
+    def jit(*args, **kwargs):  # type: ignore[no-redef,misc]
         def decorator(func):
             return func
 
@@ -561,7 +565,7 @@ def compute_dichroic_reflectance(
 
 def refract_vector_snell(
     v_in: np.ndarray, n_hat: np.ndarray, n1: float, n2: float
-) -> tuple[np.ndarray | None, bool]:
+) -> tuple[np.ndarray, bool]:
     """
     Apply Snell's law to refract a ray at an interface.
 
@@ -572,9 +576,9 @@ def refract_vector_snell(
         n2: Refractive index of transmitted medium
 
     Returns:
-        Tuple of (refracted_direction, is_total_reflection)
-        - refracted_direction: Refracted ray direction (normalized),
-          or None if total internal reflection
+        Tuple of (direction, is_total_reflection)
+        - direction: Refracted ray direction (normalized), or the reflected
+          direction if total internal reflection occurs
         - is_total_reflection: True if total internal reflection occurs
 
     Physics:
diff --git a/src/optiverse/objects/definitions_loader.py b/src/optiverse/objects/definitions_loader.py
index aa826908..8410803e 100644
--- a/src/optiverse/objects/definitions_loader.py
+++ b/src/optiverse/objects/definitions_loader.py
@@ -25,12 +25,17 @@ def _iter_component_json_files(library_path: Path | None = None) -> list[Path]:
         library_path: Optional custom library path. If None, uses built-in library.
 
     Returns:
-        List of Path objects to component folders
+        List of Path objects to component folders, sorted by folder name for a
+        deterministic order across platforms (iterdir() order is filesystem
+        dependent and differs between Linux/Windows/macOS).
     """
     root = library_path if library_path else _library_root()
     if not root.exists():
         return []
-    return [p for p in root.iterdir() if p.is_dir() and (p / "component.json").exists()]
+    folders = [
+        p for p in root.iterdir() if p.is_dir() and (p / "component.json").exists()
+    ]
+    return sorted(folders, key=lambda p: p.name)
 
 
 def load_component_records(
diff --git a/src/optiverse/ui/theme_manager.py b/src/optiverse/ui/theme_manager.py
index 5a504f65..0f6819a9 100644
--- a/src/optiverse/ui/theme_manager.py
+++ b/src/optiverse/ui/theme_manager.py
@@ -208,6 +208,31 @@ def _create_light_palette() -> QtGui.QPalette:
     return palette
 
 
+def _set_color_scheme(dark_mode: bool) -> None:
+    """
+    Pin Qt's color scheme so native styling matches the applied theme.
+
+    Uses ``QStyleHints.setColorScheme`` (Qt 6.8+). On older Qt versions the
+    setter is unavailable and this is a no-op - the QSS/palette still apply,
+    only the native-chrome override (e.g. Windows dark-mode menu bar) is
+    unavailable to correct.
+
+    Args:
+        dark_mode: True to request the dark color scheme, False for light.
+    """
+    style_hints = QtGui.QGuiApplication.styleHints()
+    setter = getattr(style_hints, "setColorScheme", None)
+    if setter is None:
+        return
+    scheme = (
+        QtCore.Qt.ColorScheme.Dark if dark_mode else QtCore.Qt.ColorScheme.Light
+    )
+    try:
+        setter(scheme)
+    except (AttributeError, TypeError) as e:
+        _logger.debug("Could not set color scheme: %s", e)
+
+
 def apply_theme(dark_mode: bool) -> None:
     """
     Apply the appropriate theme (stylesheet + palette) based on dark mode setting.
@@ -225,6 +250,16 @@ def apply_theme(dark_mode: bool) -> None:
         _logger.warning("No QApplication instance - cannot apply theme")
         return
 
+    # Pin Qt's color scheme to match the app theme.
+    #
+    # On Windows 11, Qt's native style paints native chrome (most visibly the
+    # QMenuBar's top-level items) using the OS color scheme, ignoring the QSS
+    # `color` and the application palette. When the OS is in dark mode but the
+    # app is in light mode, this renders white menu-bar text on the light
+    # menu-bar background - i.e. invisible. Forcing the color scheme keeps the
+    # native rendering consistent with the theme we actually applied.
+    _set_color_scheme(dark_mode)
+
     # Apply stylesheet and palette
     if dark_mode:
         app.setStyleSheet(get_dark_stylesheet())