From cc3c7ba532f75617505bb41297651a5c14f71bdd Mon Sep 17 00:00:00 2001
From: Claire <claire.github-309c@sitedethib.com>
Date: Fri, 16 Jan 2026 16:55:16 +0100
Subject: [PATCH] Fix `system` theme being included twice (#37526)

---
 app/helpers/theme_helper.rb       | 12 ++++--------
 spec/helpers/theme_helper_spec.rb | 14 +++-----------
 2 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/app/helpers/theme_helper.rb b/app/helpers/theme_helper.rb
index e765541414..f651a495ff 100644
--- a/app/helpers/theme_helper.rb
+++ b/app/helpers/theme_helper.rb
@@ -18,14 +18,10 @@ module ThemeHelper
   end
 
   def theme_style_tags(theme)
-    if theme == 'system'
-      ''.html_safe.tap do |tags|
-        tags << vite_stylesheet_tag('themes/mastodon-light', type: :virtual, media: 'not all and (prefers-color-scheme: dark)', crossorigin: 'anonymous')
-        tags << vite_stylesheet_tag('themes/default', type: :virtual, media: '(prefers-color-scheme: dark)', crossorigin: 'anonymous')
-      end
-    else
-      vite_stylesheet_tag "themes/#{theme}", type: :virtual, media: 'all', crossorigin: 'anonymous'
-    end
+    # TODO: get rid of that when we retire the themes and perform the settings migration
+    theme = 'default' if %w(mastodon-light contrast system).include?(theme)
+
+    vite_stylesheet_tag "themes/#{theme}", type: :virtual, media: 'all', crossorigin: 'anonymous'
   end
 
   def theme_color_tags(color_scheme)
diff --git a/spec/helpers/theme_helper_spec.rb b/spec/helpers/theme_helper_spec.rb
index 35798cced6..a402885711 100644
--- a/spec/helpers/theme_helper_spec.rb
+++ b/spec/helpers/theme_helper_spec.rb
@@ -9,17 +9,10 @@ RSpec.describe ThemeHelper do
     context 'when using "system" theme' do
       let(:theme) { 'system' }
 
-      it 'returns the mastodon-light and application stylesheets with correct color schemes' do
+      it 'returns the default theme' do
         expect(html_links.first.attributes.symbolize_keys)
           .to include(
-            # This is now identical to the default theme & will be unified very soon
-            href: have_attributes(value: match(/default/)),
-            media: have_attributes(value: 'not all and (prefers-color-scheme: dark)')
-          )
-        expect(html_links.last.attributes.symbolize_keys)
-          .to include(
-            href: have_attributes(value: match(/default/)),
-            media: have_attributes(value: '(prefers-color-scheme: dark)')
+            href: have_attributes(value: match(/default/))
           )
       end
     end
@@ -41,8 +34,7 @@ RSpec.describe ThemeHelper do
       it 'returns the theme stylesheet without color scheme information' do
         expect(html_links.first.attributes.symbolize_keys)
           .to include(
-            href: have_attributes(value: match(/default/)),
-            media: have_attributes(value: 'all')
+            href: have_attributes(value: match(/default/))
           )
       end
     end