src/Tools/VSCode/src/protocol.scala

         "completionProvider" -> Map("resolveProvider" -> false, "triggerCharacters" -> Nil),
         "hoverProvider" -> true,
         "definitionProvider" -> true,
         "documentHighlightProvider" -> true)
   }
+
+  object Initialized extends Notification0("initialized")
 
   object Shutdown extends Request0("shutdown")
   {
     def reply(id: Id, error: String): JSON.T =
       ResponseMessage.strict(id, Some("OK"), error)