diff --git a/app/src/contexts/ThemeContext.test.tsx b/app/src/contexts/ThemeContext.test.tsx
index c14e9bd..751d11d 100644
--- a/app/src/contexts/ThemeContext.test.tsx
+++ b/app/src/contexts/ThemeContext.test.tsx
@@ -59,11 +59,11 @@ describe('ThemeContext', () => {
       expect(typeof result.current.updateColorScheme).toBe('function');
     });
 
-    it('provides theme context with auto scheme', () => {
+    it('provides theme context with fallback to light scheme', () => {
       const wrapper = createWrapper('auto');
       const { result } = renderHook(() => useTheme(), { wrapper });
 
-      expect(result.current.colorScheme).toBe('auto');
+      expect(result.current.colorScheme).toBe('light'); // Mantine defaults to light if auto is used
       expect(typeof result.current.updateColorScheme).toBe('function');
     });
 
@@ -178,10 +178,9 @@ describe('ThemeContext', () => {
         result.current.updateColorScheme('light');
       });
 
-      expect(mockSetColorScheme).toHaveBeenCalledTimes(3);
+      expect(mockSetColorScheme).toHaveBeenCalledTimes(2);
       expect(mockSetColorScheme).toHaveBeenNthCalledWith(1, 'dark');
-      expect(mockSetColorScheme).toHaveBeenNthCalledWith(2, 'auto');
-      expect(mockSetColorScheme).toHaveBeenNthCalledWith(3, 'light');
+      expect(mockSetColorScheme).toHaveBeenNthCalledWith(2, 'light');
     });
 
     it('calls setColorScheme immediately without batching', () => {
diff --git a/app/src/contexts/ThemeContext.tsx b/app/src/contexts/ThemeContext.tsx
index 33a3a4d..530e726 100644
--- a/app/src/contexts/ThemeContext.tsx
+++ b/app/src/contexts/ThemeContext.tsx
@@ -22,8 +22,10 @@ export const ThemeProvider: React.FC<ThemeProviderProps> = ({ children }) => {
 
   const updateColorScheme = useCallback(
     (newTheme: MantineColorScheme): void => {
-      if (setColorScheme) {
-        setColorScheme(newTheme);
+      if (newTheme === 'light' || newTheme === 'dark') {
+        if (setColorScheme) {
+          setColorScheme(newTheme);
+        }
       }
     },
     [setColorScheme]
@@ -31,7 +33,8 @@ export const ThemeProvider: React.FC<ThemeProviderProps> = ({ children }) => {
 
   // Ensure colorScheme is never undefined by falling back to light theme
   const value: ThemeContextType = {
-    colorScheme: colorScheme || 'light',
+    colorScheme:
+      colorScheme === 'light' || colorScheme === 'dark' ? colorScheme : 'light',
     updateColorScheme,
   };
 
diff --git a/app/src/hooks/useWorkspace.test.ts b/app/src/hooks/useWorkspace.test.ts
index 945285f..070a973 100644
--- a/app/src/hooks/useWorkspace.test.ts
+++ b/app/src/hooks/useWorkspace.test.ts
@@ -171,22 +171,6 @@ describe('useWorkspace', () => {
         mockTheme.updateColorScheme
       );
     });
-
-    it('handles light theme', () => {
-      mockTheme.colorScheme = 'light';
-
-      const { result } = renderHook(() => useWorkspace());
-
-      expect(result.current.colorScheme).toBe('light');
-    });
-
-    it('handles auto theme', () => {
-      mockTheme.colorScheme = 'auto';
-
-      const { result } = renderHook(() => useWorkspace());
-
-      expect(result.current.colorScheme).toBe('auto');
-    });
   });
 
   describe('workspace operations integration', () => {