diff -r bd5ee3148132 -r 042180540068 src/Pure/Thy/sessions.scala
--- a/src/Pure/Thy/sessions.scala	Sat Nov 28 16:25:29 2020 +0100
+++ b/src/Pure/Thy/sessions.scala	Sat Nov 28 17:38:03 2020 +0100
@@ -49,7 +49,6 @@
 
   sealed case class Base(
     pos: Position.T = Position.none,
-    doc_names: List[String] = Nil,
     session_directories: Map[JFile, String] = Map.empty,
     global_theories: Map[String, String] = Map.empty,
     session_theories: List[Document.Node.Name] = Nil,
@@ -142,8 +141,6 @@
       }
     }
 
-    val doc_names = Doc.doc_names()
-
     val bootstrap =
       Sessions.Base.bootstrap(
         sessions_structure.session_directories,
@@ -325,7 +322,6 @@
             val base =
               Base(
                 pos = info.pos,
-                doc_names = doc_names,
                 session_directories = sessions_structure.session_directories,
                 global_theories = sessions_structure.global_theories,
                 session_theories = session_theories,