diff -r a43e39c52f26 -r e8959b23208b src/Pure/PIDE/prover.scala
--- a/src/Pure/PIDE/prover.scala	Wed Feb 12 00:53:15 2025 +0100
+++ b/src/Pure/PIDE/prover.scala	Wed Feb 12 13:31:06 2025 +0100
@@ -215,7 +215,7 @@
 
     Isabelle_Thread.fork(name = name) {
       try {
-        var result = new StringBuilder(100)
+        val result = new StringBuilder(100)
         var finished = false
         while (!finished) {
           //{{{