diff --git a/apps/x/apps/main/src/main.ts b/apps/x/apps/main/src/main.ts
index 6ddab7bc..d73ae442 100644
--- a/apps/x/apps/main/src/main.ts
+++ b/apps/x/apps/main/src/main.ts
@@ -64,6 +64,8 @@ function createWindow() {
   const win = new BrowserWindow({
     width: 1280,
     height: 800,
+    show: false, // Don't show until ready
+    backgroundColor: "#252525", // Prevent white flash (matches dark mode)
     webPreferences: {
       // IMPORTANT: keep Node out of renderer
       nodeIntegration: false,
@@ -73,6 +75,11 @@ function createWindow() {
     },
   });
 
+  // Show window when content is ready to prevent blank screen
+  win.once("ready-to-show", () => {
+    win.show();
+  });
+
   // Open external links in system browser (not sandboxed Electron window)
   // This handles window.open() and target="_blank" links
   win.webContents.setWindowOpenHandler(({ url }) => {
diff --git a/apps/x/apps/renderer/index.html b/apps/x/apps/renderer/index.html
index 1803a850..856065c2 100644
--- a/apps/x/apps/renderer/index.html
+++ b/apps/x/apps/renderer/index.html
@@ -5,6 +5,22 @@
     <link rel="icon" type="image/svg+xml" href="/vite.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Rowboat</title>
+    <style>
+      /* Prevent flash of white background before CSS loads */
+      html, body { margin: 0; padding: 0; }
+      html.dark, html.dark body { background-color: #252525; }
+      html.light, html.light body { background-color: #fff; }
+    </style>
+    <script>
+      // Apply theme class immediately before render
+      (function() {
+        var stored = localStorage.getItem('rowboat-theme');
+        var prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
+        var theme = stored || 'system';
+        var resolved = theme === 'system' ? (prefersDark ? 'dark' : 'light') : theme;
+        document.documentElement.classList.add(resolved);
+      })();
+    </script>
   </head>
   <body>
     <div id="root"></div>
