src/Pure/Tools/build_process.scala

--- a/src/Pure/Tools/build_process.scala	Sat Feb 11 22:59:23 2023 +0100
+++ b/src/Pure/Tools/build_process.scala	Sat Feb 11 23:02:51 2023 +0100
@@ -121,5 +121,8 @@
   ) {
     def apply(session: String): Session_Context =
       sessions.getOrElse(session, Session_Context.empty(session, Time.zero))
+
+    def is_inner(session: String): Boolean =
+      !sessions_structure.build_graph.is_maximal(session)
   }
 }