diff --git a/CHANGELOG.md b/CHANGELOG.md
index c50a398..9a2974d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.20.28] - 2026-04-20
+
+### Fixed
+- Dark mode "System" setting now reliably follows the OS preference on every page load, even in browsers where JavaScript `matchMedia` is restricted (e.g. Brave with fingerprint protection); CSS `@media (prefers-color-scheme: dark)` now serves as the authoritative source for system preference detection instead of JS
+
 ## [0.20.27] - 2026-04-20
 
 ### Fixed
diff --git a/package-lock.json b/package-lock.json
index 9d28d66..f2d06ee 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "oikos",
-  "version": "0.20.27",
+  "version": "0.20.28",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "oikos",
-      "version": "0.20.27",
+      "version": "0.20.28",
       "license": "MIT",
       "dependencies": {
         "bcrypt": "^6.0.0",
diff --git a/package.json b/package.json
index fe246fe..15b404b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.20.27",
+  "version": "0.20.28",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",
diff --git a/public/index.html b/public/index.html
index 8d2021c..f878f22 100644
--- a/public/index.html
+++ b/public/index.html
@@ -40,24 +40,18 @@
   <link rel="stylesheet" href="/styles/login.css" />
   <link rel="stylesheet" href="/styles/reminders.css" />
 
-  <!-- Theme: Vor CSS-Rendering anwenden (Flash-Prevention + System-Sync).
-       Setzt data-theme einmalig beim Laden, damit tokens.css nur [data-theme="dark"]
-       braucht — kein duplizierter @media-Block mehr nötig. -->
+  <!-- Theme: explizite Nutzer-Overrides vor CSS-Rendering anwenden (Flash-Prevention).
+       System-Präferenz wird durch @media (prefers-color-scheme: dark) in tokens.css
+       direkt per CSS behandelt — kein JS-matchMedia erforderlich. -->
   <script>
     (function() {
       var stored = localStorage.getItem('oikos-theme');
-      var prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
-      if (stored === 'dark' || stored === 'light') {
-        document.documentElement.setAttribute('data-theme', stored);
-      } else {
-        document.documentElement.setAttribute('data-theme', prefersDark ? 'dark' : 'light');
+      if (stored === 'dark') {
+        document.documentElement.setAttribute('data-theme', 'dark');
+      } else if (stored === 'light') {
+        document.documentElement.setAttribute('data-theme', 'light');
       }
-      window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', function(e) {
-        var current = localStorage.getItem('oikos-theme');
-        if (!current || current === 'system') {
-          document.documentElement.setAttribute('data-theme', e.matches ? 'dark' : 'light');
-        }
-      });
+      // System/null: tokens.css @media (prefers-color-scheme: dark) übernimmt
     })();
   </script>
 
diff --git a/public/pages/settings.js b/public/pages/settings.js
index d561448..cbe4479 100644
--- a/public/pages/settings.js
+++ b/public/pages/settings.js
@@ -851,11 +851,13 @@ function currentTheme() {
 
 function applyTheme(value) {
   localStorage.setItem('oikos-theme', value);
-  if (value === 'light' || value === 'dark') {
-    document.documentElement.setAttribute('data-theme', value);
+  if (value === 'dark') {
+    document.documentElement.setAttribute('data-theme', 'dark');
+  } else if (value === 'light') {
+    document.documentElement.setAttribute('data-theme', 'light');
   } else {
-    const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
-    document.documentElement.setAttribute('data-theme', prefersDark ? 'dark' : 'light');
+    document.documentElement.removeAttribute('data-theme');
+    // tokens.css @media (prefers-color-scheme: dark) übernimmt sofort
   }
 }
 
diff --git a/public/styles/tokens.css b/public/styles/tokens.css
index 46fba92..3657df6 100644
--- a/public/styles/tokens.css
+++ b/public/styles/tokens.css
@@ -415,10 +415,105 @@
 /* ================================================================
  * Dark Mode — private Tokens überschreiben, öffentliche API bleibt stabil.
  *
- * data-theme="dark" wird durch das Head-Script in index.html gesetzt —
- * sowohl für manuelle Overrides als auch für System-Präferenz (via
- * matchMedia-Listener). Ein einziger Selektor reicht, kein @media-Duplikat.
+ * Zwei Selektoren aktivieren Dark Mode:
+ *   1. @media (prefers-color-scheme: dark) — System-Präferenz (CSS-native,
+ *      kein JS erforderlich, funktioniert auch wenn matchMedia blockiert ist)
+ *   2. [data-theme="dark"] — expliziter Override durch den Nutzer
+ *
+ * Explizites Light ([data-theme="light"]) blockiert den @media-Block via :not().
+ * Explizites Dark ([data-theme="dark"]) überschreibt den @media-Block, falls OS
+ * auf Light steht.
  * ================================================================ */
+@media (prefers-color-scheme: dark) {
+  :root:not([data-theme="light"]) {
+    /* Neutral-Skala invertiert (warm-dunkel) */
+    --_neutral-50:  #1A1A18;
+    --_neutral-100: #222220;
+    --_neutral-150: #2A2A28;
+    --_neutral-200: #333331;
+    --_neutral-250: #3D3D3A;
+    --_neutral-300: #48484A;
+    --_neutral-400: #636360;
+    --_neutral-500: #8E8D89;
+    --_neutral-600: #AEADB0;
+    --_neutral-700: #C8C7C3;
+    --_neutral-800: #E2E1DC;
+    --_neutral-900: #F5F4F1;
+    --_neutral-950: #FAFAF8;
+
+    --_color-surface:   #2A2A28;
+    --_color-surface-3: #333331;
+
+    --_sidebar-bg:           #1A1A18;
+    --_sidebar-shadow-light: rgba(255, 255, 255, 0.04);
+    --_sidebar-shadow-dark:  rgba(0, 0, 0, 0.4);
+
+    --_color-accent:            #818CF8;
+    --_color-accent-hover:      #6366F1;
+    --_color-accent-active:     #4F46E5;
+    --_color-accent-light:      #2E2D5B;
+    --_color-accent-subtle:     #252255;
+    --_color-btn-primary:       #6366F1;
+    --_color-btn-primary-hover: #4F46E5;
+    --_color-accent-secondary:  #A78BFA;
+
+    --_color-success:       #4ADE80;
+    --_color-warning:       #F59E0B;
+    --_color-danger:        #FCA5A5;
+    --_color-text-tertiary: #A3A3A0;
+    --_color-success-light: #1A3325;
+    --_color-warning-light: #332400;
+    --_color-danger-light:  #3D1C1A;
+    --_color-info-light:    #1A2D40;
+
+    --_module-dashboard: #818CF8;
+    --_module-tasks:     #4ADE80;
+    --_module-calendar:  #A78BFA;
+    --_module-meals:     #FB923C;
+    --_module-shopping:  #F472B6;
+    --_module-notes:     #FCD34D;
+    --_module-contacts:  #60A5FA;
+    --_module-budget:    #2DD4BF;
+    --_module-settings:  #94A3B8;
+
+    --_meal-breakfast:       #F59E0B;
+    --_meal-breakfast-light: #332400;
+    --_meal-lunch-light:     #1A3325;
+    --_meal-dinner:          #818CF8;
+    --_meal-dinner-light:    #2E2D5B;
+    --_meal-snack-light:     #3D2010;
+
+    --_color-priority-none-bg:   rgba(142, 141, 137, 0.12);
+    --_color-priority-low-bg:    rgba(142, 141, 137, 0.18);
+    --_color-priority-medium-bg: rgba(230, 147, 10, 0.18);
+    --_color-priority-high-bg:   rgba(212, 81, 30, 0.18);
+    --_color-priority-urgent-bg: rgba(229, 83, 75, 0.18);
+
+    --_color-overlay:       rgba(0, 0, 0, 0.6);
+    --_color-overlay-light: rgba(0, 0, 0, 0.35);
+
+    --_shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.25);
+    --_shadow-md: 0 4px 12px rgba(0, 0, 0, 0.35);
+    --_shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.45);
+
+    --_glass-bg:               rgba(40, 40, 38, 0.75);
+    --_glass-bg-hover:         rgba(50, 50, 48, 0.82);
+    --_glass-bg-elevated:      rgba(58, 58, 55, 0.90);
+    --_glass-border:           rgba(255, 255, 255, 0.12);
+    --_glass-border-subtle:    rgba(255, 255, 255, 0.07);
+    --_glass-highlight:        rgba(255, 255, 255, 0.10);
+    --_glass-highlight-subtle: rgba(255, 255, 255, 0.06);
+    --_glass-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.30), 0 0 0 1px rgba(255, 255, 255, 0.08);
+    --_glass-shadow-md: 0 4px 20px rgba(0, 0, 0, 0.40), 0 0 0 1px rgba(255, 255, 255, 0.07);
+    --_glass-shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.55), 0 0 0 1px rgba(255, 255, 255, 0.06);
+    --_glass-bg-card:          rgba(38, 38, 36, 0.50);
+    --_glass-bg-card-hover:    rgba(48, 48, 46, 0.62);
+    --_glass-bg-input:         rgba(34, 34, 32, 0.45);
+    --_glass-bg-toolbar:       rgba(40, 40, 38, 0.55);
+    --_glass-tint-strength:    8%;
+  }
+}
+
 [data-theme="dark"] {
     /* Neutral-Skala invertiert (warm-dunkel) */
     --_neutral-50:  #1A1A18;