diff --git a/ui/desktop/eslint.config.js b/ui/desktop/eslint.config.js
index 2241702d0e63..391d45a90ffa 100644
--- a/ui/desktop/eslint.config.js
+++ b/ui/desktop/eslint.config.js
@@ -85,6 +85,7 @@ module.exports = [
         HeadersInit: 'readonly',
         KeyboardEvent: 'readonly',
         MouseEvent: 'readonly', // Add MouseEvent
+        Event: 'readonly', // Add Event
         Node: 'readonly', // Add Node
         React: 'readonly',
         handleAction: 'readonly',
diff --git a/ui/desktop/src/App.tsx b/ui/desktop/src/App.tsx
index 5fa3fde7a047..12be1661b463 100644
--- a/ui/desktop/src/App.tsx
+++ b/ui/desktop/src/App.tsx
@@ -508,6 +508,47 @@ export function AppInner() {
     };
   }, []);
 
+  useEffect(() => {
+    if (!window.electron) return;
+
+    const handleThemeChanged = (_event: unknown, ...args: unknown[]) => {
+      const themeData = args[0] as { mode: string; useSystemTheme: boolean; theme: string };
+
+      if (themeData.useSystemTheme) {
+        localStorage.setItem('use_system_theme', 'true');
+      } else {
+        localStorage.setItem('use_system_theme', 'false');
+        localStorage.setItem('theme', themeData.theme);
+      }
+
+      const isDark = themeData.useSystemTheme
+        ? window.matchMedia('(prefers-color-scheme: dark)').matches
+        : themeData.mode === 'dark';
+
+      if (isDark) {
+        document.documentElement.classList.add('dark');
+        document.documentElement.classList.remove('light');
+      } else {
+        document.documentElement.classList.remove('dark');
+        document.documentElement.classList.add('light');
+      }
+
+      const storageEvent = new Event('storage') as Event & {
+        key: string | null;
+        newValue: string | null;
+      };
+      storageEvent.key = themeData.useSystemTheme ? 'use_system_theme' : 'theme';
+      storageEvent.newValue = themeData.useSystemTheme ? 'true' : themeData.theme;
+      window.dispatchEvent(storageEvent);
+    };
+
+    window.electron.on('theme-changed', handleThemeChanged);
+
+    return () => {
+      window.electron.off('theme-changed', handleThemeChanged);
+    };
+  }, []);
+
   if (fatalError) {
     return <ErrorUI error={new Error(fatalError)} />;
   }
diff --git a/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx b/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx
index f9499fb59916..7fd1d438f9f3 100644
--- a/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx
+++ b/ui/desktop/src/components/GooseSidebar/ThemeSelector.tsx
@@ -8,37 +8,67 @@ interface ThemeSelectorProps {
   horizontal?: boolean;
 }
 
+const getIsDarkMode = (mode: 'light' | 'dark' | 'system'): boolean => {
+  if (mode === 'system') {
+    return window.matchMedia('(prefers-color-scheme: dark)').matches;
+  }
+  return mode === 'dark';
+};
+
+const getThemeMode = (): 'light' | 'dark' | 'system' => {
+  const savedUseSystemTheme = localStorage.getItem('use_system_theme');
+  if (savedUseSystemTheme === 'true') {
+    return 'system';
+  }
+
+  const savedTheme = localStorage.getItem('theme');
+  if (savedTheme) {
+    return savedTheme === 'dark' ? 'dark' : 'light';
+  }
+
+  return getIsDarkMode('system') ? 'dark' : 'light';
+};
+
+const setThemeModeStorage = (mode: 'light' | 'dark' | 'system') => {
+  if (mode === 'system') {
+    localStorage.setItem('use_system_theme', 'true');
+  } else {
+    localStorage.setItem('use_system_theme', 'false');
+    localStorage.setItem('theme', mode);
+  }
+
+  const themeData = {
+    mode,
+    useSystemTheme: mode === 'system',
+    theme: mode === 'system' ? '' : mode,
+  };
+
+  window.electron?.broadcastThemeChange(themeData);
+};
+
 const ThemeSelector: React.FC<ThemeSelectorProps> = ({
   className = '',
   hideTitle = false,
   horizontal = false,
 }) => {
-  const [themeMode, setThemeMode] = useState<'light' | 'dark' | 'system'>(() => {
-    const savedUseSystemTheme = localStorage.getItem('use_system_theme') === 'true';
-    if (savedUseSystemTheme) {
-      return 'system';
-    }
-    const savedTheme = localStorage.getItem('theme');
-    return savedTheme === 'dark' ? 'dark' : 'light';
-  });
-
-  const [isDarkMode, setDarkMode] = useState(() => {
-    // First check localStorage to determine the intended theme
-    const savedUseSystemTheme = localStorage.getItem('use_system_theme') === 'true';
-    const savedTheme = localStorage.getItem('theme');
-
-    if (savedUseSystemTheme) {
-      // Use system preference
-      const systemPrefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
-      return systemPrefersDark;
-    } else if (savedTheme) {
-      // Use saved theme preference
-      return savedTheme === 'dark';
-    } else {
-      // Fallback: check current DOM state to maintain consistency
-      return document.documentElement.classList.contains('dark');
-    }
-  });
+  const [themeMode, setThemeMode] = useState<'light' | 'dark' | 'system'>(getThemeMode);
+  const [isDarkMode, setDarkMode] = useState(() => getIsDarkMode(getThemeMode()));
+
+  useEffect(() => {
+    const handleStorageChange = (e: { key: string | null; newValue: string | null }) => {
+      if (e.key === 'use_system_theme' || e.key === 'theme') {
+        const newThemeMode = getThemeMode();
+        setThemeMode(newThemeMode);
+        setDarkMode(getIsDarkMode(newThemeMode));
+      }
+    };
+
+    window.addEventListener('storage', handleStorageChange);
+
+    return () => {
+      window.removeEventListener('storage', handleStorageChange);
+    };
+  }, []);
 
   useEffect(() => {
     const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
@@ -51,14 +81,8 @@ const ThemeSelector: React.FC<ThemeSelectorProps> = ({
 
     mediaQuery.addEventListener('change', handleThemeChange);
 
-    if (themeMode === 'system') {
-      setDarkMode(mediaQuery.matches);
-      localStorage.setItem('use_system_theme', 'true');
-    } else {
-      setDarkMode(themeMode === 'dark');
-      localStorage.setItem('use_system_theme', 'false');
-      localStorage.setItem('theme', themeMode);
-    }
+    setThemeModeStorage(themeMode);
+    setDarkMode(getIsDarkMode(themeMode));
 
     return () => mediaQuery.removeEventListener('change', handleThemeChange);
   }, [themeMode]);
diff --git a/ui/desktop/src/main.ts b/ui/desktop/src/main.ts
index c13d472d4b4e..c78b59010557 100644
--- a/ui/desktop/src/main.ts
+++ b/ui/desktop/src/main.ts
@@ -2009,6 +2009,17 @@ async function appMain() {
     }
   });
 
+  ipcMain.on('broadcast-theme-change', (event, themeData) => {
+    const senderWindow = BrowserWindow.fromWebContents(event.sender);
+    const allWindows = BrowserWindow.getAllWindows();
+
+    allWindows.forEach((window) => {
+      if (window.id !== senderWindow?.id) {
+        window.webContents.send('theme-changed', themeData);
+      }
+    });
+  });
+
   ipcMain.on('reload-app', (event) => {
     // Get the window that sent the event
     const window = BrowserWindow.fromWebContents(event.sender);
diff --git a/ui/desktop/src/preload.ts b/ui/desktop/src/preload.ts
index 58f1b6c5b794..654c558412fa 100644
--- a/ui/desktop/src/preload.ts
+++ b/ui/desktop/src/preload.ts
@@ -95,6 +95,11 @@ type ElectronAPI = {
     callback: (event: Electron.IpcRendererEvent, ...args: unknown[]) => void
   ) => void;
   emit: (channel: string, ...args: unknown[]) => void;
+  broadcastThemeChange: (themeData: {
+    mode: string;
+    useSystemTheme: boolean;
+    theme: string;
+  }) => void;
   // Functions for image pasting
   saveDataUrlToTemp: (dataUrl: string, uniqueId: string) => Promise<SaveDataUrlResponse>;
   deleteTempFile: (filePath: string) => void;
@@ -209,6 +214,9 @@ const electronAPI: ElectronAPI = {
   emit: (channel: string, ...args: unknown[]) => {
     ipcRenderer.emit(channel, ...args);
   },
+  broadcastThemeChange: (themeData: { mode: string; useSystemTheme: boolean; theme: string }) => {
+    ipcRenderer.send('broadcast-theme-change', themeData);
+  },
   saveDataUrlToTemp: (dataUrl: string, uniqueId: string): Promise<SaveDataUrlResponse> => {
     return ipcRenderer.invoke('save-data-url-to-temp', dataUrl, uniqueId);
   },
diff --git a/ui/desktop/src/utils/ollamaDetection.test.ts b/ui/desktop/src/utils/ollamaDetection.test.ts
index 8048b20187c0..07da6071b074 100644
--- a/ui/desktop/src/utils/ollamaDetection.test.ts
+++ b/ui/desktop/src/utils/ollamaDetection.test.ts
@@ -1,5 +1,5 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
-/* global AbortSignal, TextEncoder, Event, EventListener */
+/* global AbortSignal, TextEncoder, EventListener */
 
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import {