diff --git a/web/src/App.tsx b/web/src/App.tsx
index 17bc640..a4b9c86 100644
--- a/web/src/App.tsx
+++ b/web/src/App.tsx
@@ -89,6 +89,11 @@ export default function App() {
   // Theme anwenden/persistieren
   useEffect(() => {
     document.body.setAttribute('data-theme', theme);
+    if (import.meta.env.VITE_BUILD_CHANNEL === 'nightly') {
+      document.body.setAttribute('data-build', 'nightly');
+    } else {
+      document.body.removeAttribute('data-build');
+    }
     localStorage.setItem('theme', theme);
   }, [theme]);
 
diff --git a/web/src/styles.css b/web/src/styles.css
index 928b377..dd346bd 100644
--- a/web/src/styles.css
+++ b/web/src/styles.css
@@ -303,6 +303,12 @@ body {
 
 .container { width: 90vw; max-width: 1800px; margin: 0 auto; padding: 28px; }
 
+/* Nightly Build: volle Breite (mind. 90% der Anzeige), kein max-width-Limit */
+[data-build="nightly"] .container {
+  width: 90vw;
+  max-width: none;
+}
+
 /* Neuer Header-Style basierend auf Google Stitch Design */
 header { 
   display: flex;