diff --git a/src/cascadia/TerminalControl/ControlCore.cpp b/src/cascadia/TerminalControl/ControlCore.cpp
index 1e41fdb5c..53f8b99a8 100644
--- a/src/cascadia/TerminalControl/ControlCore.cpp
+++ b/src/cascadia/TerminalControl/ControlCore.cpp
@@ -435,14 +435,14 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             return;
         }
 
-        auto newOpacity = std::clamp(_settings.Opacity() + adjustment,
+        auto newOpacity = std::clamp(Opacity() + adjustment,
                                      0.0,
                                      1.0);
 
         // GH#5098: Inform the engine of the new opacity of the default text background.
         SetBackgroundOpacity(::base::saturated_cast<float>(newOpacity));
 
-        _settings.Opacity(newOpacity);
+        Opacity(newOpacity);
 
         auto eventArgs = winrt::make_self<TransparencyChangedEventArgs>(newOpacity);
         _TransparencyChangedHandlers(*this, *eventArgs);
@@ -569,6 +569,8 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         _settings = settings;
 
+        _runtimeOpacity = std::nullopt;
+
         // Initialize our font information.
         const auto fontFace = _settings.FontFace();
         const short fontHeight = ::base::saturated_cast<short>(_settings.FontSize());
diff --git a/src/cascadia/TerminalControl/ControlCore.h b/src/cascadia/TerminalControl/ControlCore.h
index a04032ef7..7d3d406d3 100644
--- a/src/cascadia/TerminalControl/ControlCore.h
+++ b/src/cascadia/TerminalControl/ControlCore.h
@@ -30,6 +30,14 @@ namespace ControlUnitTests
     class ControlInteractivityTests;
 };
 
+#define RUNTIME_SETTING(type, name, setting)                      \
+private:                                                          \
+    std::optional<type> _runtime##name{ std::nullopt };           \
+    void name(const type newValue) { _runtime##name = newValue; } \
+                                                                  \
+public:                                                           \
+    type name() const { return _runtime##name ? *_runtime##name : setting; }
+
 namespace winrt::Microsoft::Terminal::Control::implementation
 {
     struct ControlCore : ControlCoreT<ControlCore>
@@ -149,6 +157,8 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         hstring ReadEntireBuffer() const;
 
+        RUNTIME_SETTING(double, Opacity, _settings.Opacity());
+
         // -------------------------------- WinRT Events ---------------------------------
         // clang-format off
         WINRT_CALLBACK(FontSizeChanged, Control::FontSizeChangedEventArgs);
diff --git a/src/cascadia/TerminalControl/ControlCore.idl b/src/cascadia/TerminalControl/ControlCore.idl
index 84cb83e80..23f85abc9 100644
--- a/src/cascadia/TerminalControl/ControlCore.idl
+++ b/src/cascadia/TerminalControl/ControlCore.idl
@@ -47,6 +47,7 @@ namespace Microsoft.Terminal.Control
         Windows.Foundation.Size FontSize { get; };
         String FontFaceName { get; };
         UInt16 FontWeight { get; };
+        Double Opacity { get; };
 
         Boolean TrySendKeyEvent(Int16 vkey,
                              Int16 scanCode,
diff --git a/src/cascadia/TerminalControl/TermControl.cpp b/src/cascadia/TerminalControl/TermControl.cpp
index f90190a5d..fc6f882b8 100644
--- a/src/cascadia/TerminalControl/TermControl.cpp
+++ b/src/cascadia/TerminalControl/TermControl.cpp
@@ -450,7 +450,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             acrylic.TintColor(bgColor);
 
             // Apply brush settings
-            acrylic.TintOpacity(appearance.Opacity());
+            acrylic.TintOpacity(_core.Opacity());
 
             // Apply brush to control if it's not already there
             if (RootGrid().Background() != acrylic)
@@ -459,16 +459,16 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             }
 
             // GH#5098: Inform the engine of the new opacity of the default text background.
-            _core.SetBackgroundOpacity(::base::saturated_cast<float>(appearance.Opacity()));
+            _core.SetBackgroundOpacity(::base::saturated_cast<float>(_core.Opacity()));
         }
         else
         {
             Media::SolidColorBrush solidColor{};
-            solidColor.Opacity(_settings.Opacity());
+            solidColor.Opacity(_core.Opacity());
             RootGrid().Background(solidColor);
 
             // GH#5098: Inform the engine of the new opacity of the default text background.
-            _core.SetBackgroundOpacity(appearance.Opacity());
+            _core.SetBackgroundOpacity(_core.Opacity());
         }
     }
 
diff --git a/src/cascadia/TerminalSettingsModel/TerminalSettings.idl b/src/cascadia/TerminalSettingsModel/TerminalSettings.idl
index 80231906e..480f897ed 100644
--- a/src/cascadia/TerminalSettingsModel/TerminalSettings.idl
+++ b/src/cascadia/TerminalSettingsModel/TerminalSettings.idl
@@ -35,5 +35,9 @@ namespace Microsoft.Terminal.Settings.Model
         void ApplyColorScheme(ColorScheme scheme);
 
         ColorScheme AppliedColorScheme;
+
+        String Commandline { set; };
+        String StartingDirectory { set; };
+        String EnvironmentVariables { set; };
     };
 }