src/Pure/PIDE/markup.scala

         case List((FUNCTION, CANCEL_SCALA), (ID, id)) => Some(id)
         case _ => None
       }
   }
 
+  val SLEDGEHAMMER_PROVERS = "sledgehammer_provers"
+  val Sledgehammer_Provers: Properties.T = List((FUNCTION, SLEDGEHAMMER_PROVERS))
+
   object ML_Statistics
   {
     def unapply(props: Properties.T): Option[Properties.T] =
       props match {
         case (FUNCTION, "ML_statistics") :: stats => Some(stats)