diff -r 2d99f3e24da4 -r 956ecf2c07a0 src/Pure/ML/ml_settings.scala
--- a/src/Pure/ML/ml_settings.scala	Sun Jun 15 22:14:38 2025 +0200
+++ b/src/Pure/ML/ml_settings.scala	Sun Jun 15 22:46:45 2025 +0200
@@ -8,15 +8,44 @@
 
 
 object ML_Settings {
-  def system(env: Isabelle_System.Settings = Isabelle_System.Settings()): ML_Settings =
+  def system(options: Options,
+    env: Isabelle_System.Settings = Isabelle_System.Settings()
+  ): ML_Settings =
     new ML_Settings {
+      override def polyml_home: Path = Path.variable("POLYML_HOME").expand_env(env)
       override def ml_system: String = Isabelle_System.getenv_strict("ML_SYSTEM", env = env)
-      override def ml_platform: String = Isabelle_System.getenv_strict("ML_PLATFORM", env = env)
+      override def ml_platform: String = {
+        proper_string(Isabelle_System.getenv("ML_PLATFORM", env = env)) getOrElse {
+          val platform_64 =
+            Isabelle_Platform.make(env = env)
+              .ISABELLE_PLATFORM(windows = true, apple = options.bool("ML_system_apple"))
+          if (options.bool("ML_system_64")) platform_64
+          else platform_64.replace("64", "64_32")
+        }
+      }
+      override def ml_options: String =
+        proper_string(Isabelle_System.getenv("ML_OPTIONS", env = env)) getOrElse
+          Isabelle_System.getenv(if (ml_platform_is_64_32) "ML_OPTIONS32" else "ML_OPTIONS64")
     }
 }
 
 trait ML_Settings {
+  def polyml_home: Path
   def ml_system: String
   def ml_platform: String
+  def ml_options: String
+
   def ml_identifier: String = ml_system + "_" + ml_platform
+  def ml_home: Path = polyml_home + Path.basic(ml_platform)
+
+  def ml_platform_is_arm: Boolean = ml_platform.containsSlice("arm64")
+  def ml_platform_is_windows: Boolean = ml_platform.containsSlice("windows")
+  def ml_platform_is_64_32: Boolean = ml_platform.containsSlice("64_32")
+
+  def ml_sources: Path = polyml_home + Path.basic("src")
+  def ml_sources_root: (String, String) =
+    ("ML_SOURCES_ROOT", if (ml_platform_is_arm) "src/ROOT0.ML" else "src/ROOT.ML")
+
+  def polyml_exe: Path =
+    ml_home + Path.basic("poly").exe_if(ml_platform_is_windows)
 }