diff -r 2f43a87a7d06 -r a296642fa0a5 src/Pure/Build/sessions.scala
--- a/src/Pure/Build/sessions.scala	Sat Dec 07 11:13:02 2024 +0100
+++ b/src/Pure/Build/sessions.scala	Sat Dec 07 11:59:51 2024 +0100
@@ -709,6 +709,8 @@
 
     def dirs: List[Path] = dir :: directories
 
+    def unsorted_chapter: Boolean = chapter == UNSORTED
+
     def main_group: Boolean = groups.contains("main")
     def doc_group: Boolean = groups.contains("doc")