diff --git a/config/assets.php b/config/assets.php
index 25113e8..409f8fd 100644
--- a/config/assets.php
+++ b/config/assets.php
@@ -6,7 +6,6 @@ return [
             'base' => [
                 'css/app-layers.css',
                 'css/base/variables.base.css',
-                'css/base/variables.theme-dark-green.css',
                 'css/base/variables.contrast.css',
             ],
             'shared' => [
diff --git a/config/themes.php b/config/themes.php
deleted file mode 100644
index 2d461b2..0000000
--- a/config/themes.php
+++ /dev/null
@@ -1,7 +0,0 @@
-<?php
-
-return [
-    'light' => 'Light',
-    'dark' => 'Dark',
-    'dark-green' => 'Dark green',
-];
diff --git a/core/App/Container/Registrars/SettingsRegistrar.php b/core/App/Container/Registrars/SettingsRegistrar.php
index 5509b42..219b3bd 100644
--- a/core/App/Container/Registrars/SettingsRegistrar.php
+++ b/core/App/Container/Registrars/SettingsRegistrar.php
@@ -26,7 +26,6 @@ use MintyPHP\Service\Settings\SettingsSessionGateway;
 use MintyPHP\Service\Settings\SettingsSmtpGateway;
 use MintyPHP\Service\Settings\SettingsSystemAuditGateway;
 use MintyPHP\Service\Settings\SettingsUserLifecycleGateway;
-use MintyPHP\Service\Settings\ThemeConfigGateway;
 use MintyPHP\Service\Tenant\TenantService;
 
 final class SettingsRegistrar implements ContainerRegistrar
@@ -65,7 +64,6 @@ final class SettingsRegistrar implements ContainerRegistrar
             $c->get(ApiTokenRepository::class),
             $c->get(AuditRecorderInterface::class)
         ));
-        $container->set(ThemeConfigGateway::class, static fn (AppContainer $c): ThemeConfigGateway => $c->get(SettingServicesFactory::class)->createThemeConfigGateway());
         // Branding services are registered here because they depend on settings gateways
         // and are consumed alongside settings (e.g. in UserAccessPdfService and the admin UI).
         $container->set(BrandingLogoService::class, static fn (AppContainer $c): BrandingLogoService => $c->get(BrandingServicesFactory::class)->createBrandingLogoService());
diff --git a/core/Service/Settings/SettingServicesFactory.php b/core/Service/Settings/SettingServicesFactory.php
index 2f80e59..fde1ef7 100644
--- a/core/Service/Settings/SettingServicesFactory.php
+++ b/core/Service/Settings/SettingServicesFactory.php
@@ -9,7 +9,6 @@ use MintyPHP\Repository\Tenant\TenantRepositoryInterface;
 
 class SettingServicesFactory
 {
-    private ?ThemeConfigGateway $themeConfigService = null;
     private ?SettingCacheService $settingCacheService = null;
     private ?SettingsCryptoGatewayInterface $settingsCryptoGateway = null;
     private ?SettingsMetadataGateway $settingsMetadataGateway = null;
@@ -53,7 +52,6 @@ class SettingServicesFactory
     {
         return $this->settingsAppGateway ??= new SettingsAppGateway(
             $this->createSettingsMetadataGateway(),
-            $this->createThemeConfigGateway(),
         );
     }
 
@@ -108,11 +106,6 @@ class SettingServicesFactory
         );
     }
 
-    public function createThemeConfigGateway(): ThemeConfigGateway
-    {
-        return $this->themeConfigService ??= new ThemeConfigGateway();
-    }
-
     public function createSettingsCryptoGateway(): SettingsCryptoGatewayInterface
     {
         return $this->settingsCryptoGateway ??= new SettingsCryptoGateway();
diff --git a/core/Service/Settings/SettingsAppGateway.php b/core/Service/Settings/SettingsAppGateway.php
index 0f330f9..f2c0d61 100644
--- a/core/Service/Settings/SettingsAppGateway.php
+++ b/core/Service/Settings/SettingsAppGateway.php
@@ -13,15 +13,18 @@ use MintyPHP\I18n;
  *
  * The theme CATALOG utilities (listThemes, isAllowedTheme, normalizeTheme,
  * resolveDefaultTheme) stay because consumers across Tenant / Auth / User
- * flows need to validate a theme value and resolve a safe default. There is
- * no global setting lookup in these helpers anymore — the default is a
- * hardcoded 'light' falling back to the first available catalog entry.
+ * flows need to validate a theme value and resolve a safe default. The
+ * catalog is a fixed two-entry list; 'light' is the hardcoded default.
  */
 class SettingsAppGateway
 {
+    private const THEMES = [
+        'light' => 'Light',
+        'dark' => 'Dark',
+    ];
+
     public function __construct(
         private readonly SettingsMetadataGateway $settingsMetadataGateway,
-        private readonly ThemeConfigGateway $themeConfigService
     ) {
     }
 
@@ -82,14 +85,11 @@ class SettingsAppGateway
     }
 
     /**
-     * Catalog of available themes — purely code-level (config/themes.php),
-     * not a global setting.
-     *
      * @return array<string, string>
      */
     public function listThemes(): array
     {
-        return $this->themeConfigService->all();
+        return self::THEMES;
     }
 
     public function isAllowedTheme(?string $theme): bool
diff --git a/core/Service/Settings/ThemeConfigGateway.php b/core/Service/Settings/ThemeConfigGateway.php
deleted file mode 100644
index 103902f..0000000
--- a/core/Service/Settings/ThemeConfigGateway.php
+++ /dev/null
@@ -1,46 +0,0 @@
-<?php
-
-namespace MintyPHP\Service\Settings;
-
-class ThemeConfigGateway
-{
-    private const DEFAULT_THEMES = [
-        'light' => 'Light',
-        'dark' => 'Dark',
-    ];
-
-    private ?array $themes = null;
-
-    public function all(): array
-    {
-        if ($this->themes !== null) {
-            return $this->themes;
-        }
-
-        $file = dirname(__DIR__, 3) . '/config/themes.php';
-        if (!is_file($file)) {
-            $this->themes = self::DEFAULT_THEMES;
-            return $this->themes;
-        }
-
-        $loaded = include $file;
-        if (!is_array($loaded)) {
-            $this->themes = self::DEFAULT_THEMES;
-            return $this->themes;
-        }
-
-        $clean = [];
-        foreach ($loaded as $key => $label) {
-            $themeKey = strtolower(trim((string) $key));
-            $themeLabel = trim((string) $label);
-            if ($themeKey === '' || $themeLabel === '') {
-                continue;
-            }
-            $clean[$themeKey] = $themeLabel;
-        }
-
-        // Fall back to defaults if the file returns an empty or invalid list — system must always have themes.
-        $this->themes = $clean ?: self::DEFAULT_THEMES;
-        return $this->themes;
-    }
-}
diff --git a/core/Support/helpers/branding.php b/core/Support/helpers/branding.php
index adf7d9a..23c9eb7 100644
--- a/core/Support/helpers/branding.php
+++ b/core/Support/helpers/branding.php
@@ -7,18 +7,16 @@
  */
 
 /**
- * Load configured themes with a safe fallback list.
+ * Available themes. Fixed two-entry catalog — light and dark.
+ *
+ * @return array<string, string>
  */
 function appThemes(): array
 {
-    if (!class_exists('MintyPHP\\Service\\Settings\\ThemeConfigGateway')) {
-        return [
-            'light' => 'Light',
-            'dark' => 'Dark',
-        ];
-    }
-
-    return app(\MintyPHP\Service\Settings\ThemeConfigGateway::class)->all();
+    return [
+        'light' => 'Light',
+        'dark' => 'Dark',
+    ];
 }
 
 /**
diff --git a/db/updates/2026-04-24-theme-simplification.sql b/db/updates/2026-04-24-theme-simplification.sql
new file mode 100644
index 0000000..7d07799
--- /dev/null
+++ b/db/updates/2026-04-24-theme-simplification.sql
@@ -0,0 +1,7 @@
+-- Theme simplification: collapse catalog to light + dark.
+-- Migrates any leftover 'dark-green' values back to safe defaults.
+-- Idempotent — re-runs are a no-op because the WHERE clauses filter
+-- on the exact legacy value that the preceding run already replaced.
+
+UPDATE users SET theme = 'light' WHERE theme = 'dark-green';
+UPDATE tenants SET default_theme = NULL WHERE default_theme = 'dark-green';
diff --git a/i18n/default_de.json b/i18n/default_de.json
index f48b3f4..1473cfe 100644
--- a/i18n/default_de.json
+++ b/i18n/default_de.json
@@ -255,7 +255,6 @@
   "Theme": "Theme",
   "Light": "Hell",
   "Dark": "Dunkel",
-  "Dark green": "Dunkelgrün",
   "Main menu": "Hauptmenü",
   "Toggle Sidebar": "Sidebar umschalten",
   "Toggle Detail Sidebar": "Detail-Seitenleiste umschalten",
diff --git a/i18n/default_en.json b/i18n/default_en.json
index 3f79d53..50799ce 100644
--- a/i18n/default_en.json
+++ b/i18n/default_en.json
@@ -255,7 +255,6 @@
   "Theme": "Theme",
   "Light": "Light",
   "Dark": "Dark",
-  "Dark green": "Dark green",
   "Main menu": "Main menu",
   "Toggle Sidebar": "Toggle Sidebar",
   "Toggle Detail Sidebar": "Toggle Detail Sidebar",
diff --git a/tests/Architecture/ConfigContractsTest.php b/tests/Architecture/ConfigContractsTest.php
index e3b3744..eb6e260 100644
--- a/tests/Architecture/ConfigContractsTest.php
+++ b/tests/Architecture/ConfigContractsTest.php
@@ -14,7 +14,6 @@ final class ConfigContractsTest extends TestCase
             'config/assets.php',
             'config/routes.php',
             'config/modules.php',
-            'config/themes.php',
             'config/config.php.example',
         ];
         foreach ($required as $file) {
diff --git a/tests/Service/Settings/SettingsAppGatewayTest.php b/tests/Service/Settings/SettingsAppGatewayTest.php
index f431703..a913ee7 100644
--- a/tests/Service/Settings/SettingsAppGatewayTest.php
+++ b/tests/Service/Settings/SettingsAppGatewayTest.php
@@ -5,17 +5,13 @@ namespace MintyPHP\Tests\Service\Settings;
 use MintyPHP\Repository\Settings\SettingRepositoryInterface;
 use MintyPHP\Service\Settings\SettingsAppGateway;
 use MintyPHP\Service\Settings\SettingsMetadataGateway;
-use MintyPHP\Service\Settings\ThemeConfigGateway;
 use PHPUnit\Framework\TestCase;
 
 class SettingsAppGatewayTest extends TestCase
 {
     private function createGateway(SettingRepositoryInterface $settings): SettingsAppGateway
     {
-        $themeConfig = $this->createMock(ThemeConfigGateway::class);
-        $themeConfig->method('all')->willReturn(['light' => 'Light', 'dark' => 'Dark']);
-
-        return new SettingsAppGateway(new SettingsMetadataGateway($settings), $themeConfig);
+        return new SettingsAppGateway(new SettingsMetadataGateway($settings));
     }
 
     public function testGetAppTitleReturnsNullWhenEmpty(): void
diff --git a/tests/Service/Settings/SettingsGatewayNormalizationTest.php b/tests/Service/Settings/SettingsGatewayNormalizationTest.php
index 734fc83..bf2e140 100644
--- a/tests/Service/Settings/SettingsGatewayNormalizationTest.php
+++ b/tests/Service/Settings/SettingsGatewayNormalizationTest.php
@@ -8,7 +8,6 @@ use MintyPHP\Service\Settings\SettingsFrontendTelemetryGateway;
 use MintyPHP\Service\Settings\SettingsMetadataGateway;
 use MintyPHP\Service\Settings\SettingsSmtpGateway;
 use MintyPHP\Service\Settings\SettingsSystemAuditGateway;
-use MintyPHP\Service\Settings\ThemeConfigGateway;
 use PHPUnit\Framework\TestCase;
 
 final class SettingsGatewayNormalizationTest extends TestCase
@@ -124,9 +123,6 @@ final class SettingsGatewayNormalizationTest extends TestCase
 
     private function newAppGateway(SettingRepositoryInterface $settingRepository): SettingsAppGateway
     {
-        $themeConfig = $this->createMock(ThemeConfigGateway::class);
-        $themeConfig->method('all')->willReturn(['light' => 'Light', 'dark' => 'Dark']);
-
-        return new SettingsAppGateway(new SettingsMetadataGateway($settingRepository), $themeConfig);
+        return new SettingsAppGateway(new SettingsMetadataGateway($settingRepository));
     }
 }
diff --git a/tests/Support/ThemeResolutionTest.php b/tests/Support/ThemeResolutionTest.php
index 8395880..51034e5 100644
--- a/tests/Support/ThemeResolutionTest.php
+++ b/tests/Support/ThemeResolutionTest.php
@@ -4,7 +4,6 @@ namespace MintyPHP\Tests\Support;
 
 use MintyPHP\App\AppContainer;
 use MintyPHP\Service\Settings\SettingCacheService;
-use MintyPHP\Service\Settings\ThemeConfigGateway;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -27,10 +26,6 @@ class ThemeResolutionTest extends TestCase
 
         $this->container = new AppContainer();
 
-        $themeConfig = $this->createMock(ThemeConfigGateway::class);
-        $themeConfig->method('all')->willReturn(['light' => 'Light', 'dark' => 'Dark']);
-        $this->container->set(ThemeConfigGateway::class, fn () => $themeConfig);
-
         $this->setAppSettings([]);
 
         $this->pushAppContainer($this->container);
diff --git a/web/css/base/variables.base.css b/web/css/base/variables.base.css
index ccf48f2..3c59970 100644
--- a/web/css/base/variables.base.css
+++ b/web/css/base/variables.base.css
@@ -602,7 +602,7 @@
   }
 }
 
-[data-theme^="dark"] {
+[data-theme="dark"] {
   color-scheme: dark;
   --app-background-color: rgb(19, 22.5, 30.5);
   --app-sidebar-background-color: var(--app-background-color);
@@ -830,7 +830,7 @@
   --app-icon-invalid: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='rgb(149.5, 74, 80)' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='12' r='10'%3E%3C/circle%3E%3Cline x1='12' y1='8' x2='12' y2='12'%3E%3C/line%3E%3Cline x1='12' y1='16' x2='12.01' y2='16'%3E%3C/line%3E%3C/svg%3E");
 }
 
-[data-theme^="dark"]
+[data-theme="dark"]
   input:is(
     [type="submit"],
     [type="button"],
diff --git a/web/css/base/variables.contrast.css b/web/css/base/variables.contrast.css
index 2e78561..91d6bef 100644
--- a/web/css/base/variables.contrast.css
+++ b/web/css/base/variables.contrast.css
@@ -37,8 +37,8 @@ html[data-contrast="high"][data-theme="light"],
   --app-action-danger-outline-background: rgba(143, 0, 0, 0.2);
 }
 
-html[data-contrast="high"][data-theme^="dark"],
-[data-contrast="high"][data-theme^="dark"] {
+html[data-contrast="high"][data-theme="dark"],
+[data-contrast="high"][data-theme="dark"] {
   --app-background-color: #000;
   --app-sidebar-background-color: var(--app-background-color);
   --app-color: #f8fafc;
diff --git a/web/css/base/variables.theme-dark-green.css b/web/css/base/variables.theme-dark-green.css
deleted file mode 100644
index 713a86d..0000000
--- a/web/css/base/variables.theme-dark-green.css
+++ /dev/null
@@ -1,45 +0,0 @@
-@charset "UTF-8";
-
-@layer tokens {
-[data-theme="dark-green"] {
-  --app-background-color: #0f1713;
-  --app-sidebar-background-color: var(--app-background-color);
-  --app-color: #cfe0d6;
-  --app-text-selection-color: rgba(64, 170, 118, 0.25);
-  --app-muted-color: #8a9b91;
-  --app-muted-border-color: #223028;
-  --app-form-element-background-color: #141f19;
-  --app-form-element-border-color: #26362d;
-  --app-form-element-color: #d5e6dc;
-  --app-form-element-placeholder-color: #7f9187;
-  --app-card-background-color: #141f19;
-  --app-card-border-color: #223028;
-  --app-card-sectioning-background-color: #1a261f;
-  --app-details-card-open-summary-bg: #203026;
-  --app-dropdown-background-color: #141f19;
-  --app-dropdown-border-color: #223028;
-  --app-dropdown-hover-background-color: #1f2a24;
-  --app-modal-overlay-background-color: rgba(7, 10, 8, 0.75);
-  --app-progress-background-color: #223028;
-  --app-primary-h-base: 145;
-  --app-primary-s-base: 38%;
-  --app-primary-l-base: 38%;
-  --badge-success-bg: #123225;
-  --badge-success-color: #8de2b4;
-  --badge-success-border: #1f4a36;
-  --badge-danger-bg: #361a1d;
-  --badge-danger-color: #f4a3ad;
-  --badge-danger-border: #5a2b32;
-  --badge-info-bg: #142735;
-  --badge-info-color: #9ad2e0;
-  --badge-info-border: #214156;
-  --badge-warn-bg: #3a2a12;
-  --badge-warn-color: #ffdf9e;
-  --badge-warn-border: #5a401b;
-  --badge-neutral-bg: #1b2620;
-  --badge-neutral-color: #cfe0d6;
-  --badge-neutral-border: #2a3a31;
-  --app-tile-bg: rgb(20 28 24);
-  --app-blockquote-background-color: rgb(20 28 24);
-}
-}
diff --git a/web/css/vendor-overrides/gridjs.css b/web/css/vendor-overrides/gridjs.css
index f1bbfd6..48ec52b 100644
--- a/web/css/vendor-overrides/gridjs.css
+++ b/web/css/vendor-overrides/gridjs.css
@@ -691,11 +691,6 @@
     filter: invert(1);
   }
 
-  html[data-theme="dark-green"] button.gridjs-sort,
-  html[data-theme="dark-green"] button.gridjs-sort-neutral {
-    filter: invert(1);
-  }
-
   button.gridjs-sort {
     background-color: transparent;
     background-position-x: center;
diff --git a/web/js/components/app-theme-toggle.js b/web/js/components/app-theme-toggle.js
index c6b401a..11a6d5e 100644
--- a/web/js/components/app-theme-toggle.js
+++ b/web/js/components/app-theme-toggle.js
@@ -8,7 +8,7 @@ const setTheme = (theme) => {
   document.documentElement.dataset.theme = theme;
 };
 
-const isDarkTheme = (theme) => theme && theme.startsWith('dark');
+const isDarkTheme = (theme) => theme === 'dark';
 
 const setIcon = (iconEl, theme) => {
   if (!iconEl) {