diff --git a/.gitignore b/.gitignore
index 3c03c07..d093c4a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -31,7 +31,7 @@ data/
 *.swp
 *.swo
 .codex 
-
+AGENTS.md
 
 # Claude Code — share skills/agents/rules/hooks/settings; keep local permissions and worktrees out
 .claude/settings.local.json
diff --git a/public/index.html b/public/index.html
index e4a50ca..953a94c 100644
--- a/public/index.html
+++ b/public/index.html
@@ -48,6 +48,8 @@
         document.documentElement.setAttribute('data-theme', 'dark');
       } else if (stored === 'light') {
         document.documentElement.setAttribute('data-theme', 'light');
+      } else {
+        document.documentElement.removeAttribute('data-theme');
       }
       // System/null: tokens.css @media (prefers-color-scheme: dark) übernimmt
     })();
diff --git a/public/pages/settings.js b/public/pages/settings.js
index a265fa2..47f65b8 100644
--- a/public/pages/settings.js
+++ b/public/pages/settings.js
@@ -1788,15 +1788,7 @@ function currentTheme() {
 }
 
 function applyTheme(value) {
-  localStorage.setItem('oikos-theme', value);
-  if (value === 'dark') {
-    document.documentElement.setAttribute('data-theme', 'dark');
-  } else if (value === 'light') {
-    document.documentElement.setAttribute('data-theme', 'light');
-  } else {
-    document.documentElement.removeAttribute('data-theme');
-    // tokens.css @media (prefers-color-scheme: dark) übernimmt sofort
-  }
+  window.oikos?.applyTheme(value);
 }
 
 function showError(el, msg) {
diff --git a/public/router.js b/public/router.js
index 613824f..961d6a3 100644
--- a/public/router.js
+++ b/public/router.js
@@ -1199,6 +1199,16 @@ if (/iPhone|iPad|iPod/.test(navigator.userAgent)) {
 // --------------------------------------------------------
 (async () => {
   try {
+    // Vorab-Theme-Anwendung ohne Abhängigkeit von window.oikos
+    const stored = localStorage.getItem('oikos-theme');
+    if (stored === 'dark') {
+      document.documentElement.setAttribute('data-theme', 'dark');
+    } else if (stored === 'light') {
+      document.documentElement.setAttribute('data-theme', 'light');
+    } else {
+      document.documentElement.removeAttribute('data-theme');
+    }
+    
     await initI18n();
     navigate(location.pathname, false);
   } catch (err) {
@@ -1214,6 +1224,16 @@ window.oikos = {
   navigate,
   showToast,
   setThemeColor,
+  applyTheme: (value) => {
+    localStorage.setItem('oikos-theme', value);
+    if (value === 'dark') {
+      document.documentElement.setAttribute('data-theme', 'dark');
+    } else if (value === 'light') {
+      document.documentElement.setAttribute('data-theme', 'light');
+    } else {
+      document.documentElement.removeAttribute('data-theme');
+    }
+  },
   restoreThemeColor: () => {
     const route = ROUTES.find((r) => r.path === currentPath);
     updateThemeColorForRoute(route);