src/Pure/PIDE/session.scala

           output.properties match {
             case Position.Id(state_id) =>
               accumulate(state_id, output.message)
 
             case _ if output.is_init =>
+              prover.get.init_symbols()
               phase = Session.Ready
 
             case Markup.Return_Code(rc) if output.is_exit =>
               if (rc == 0) phase = Session.Inactive
               else phase = Session.Failed
               prover.reset
 
-            case _ => raw_output_messages.post(output)
+            case _ =>
+              raw_output_messages.post(output)
           }
         }
     }
     //}}}