diff -r 210be56ecd1d -r 0fa6759948bc src/Pure/System/options.scala
--- a/src/Pure/System/options.scala	Wed May 14 11:31:23 2025 +0200
+++ b/src/Pure/System/options.scala	Thu May 15 22:55:29 2025 +0200
@@ -111,6 +111,9 @@
   val TAG_COLOR_DIALOG = "color_dialog"  // special color selection dialog
   val TAG_VSCODE = "vscode"      // relevant for "isabelle vscode" and "isabelle vscode_server"
 
+  val SUFFIX_DARK = "_dark"
+  def theme_suffix(): String = if (GUI.is_dark_laf()) SUFFIX_DARK else ""
+
   case class Entry(
     public: Boolean,
     pos: Position.T,
@@ -159,6 +162,8 @@
     def for_build_sync: Boolean = for_tag(TAG_BUILD_SYNC)
     def for_vscode: Boolean = for_tag(TAG_VSCODE)
 
+    def is_dark: Boolean = name.endsWith(SUFFIX_DARK)
+
     def session_content: Boolean = for_content || for_document
   }