* Remove handling of out-of-spec 'notification/stderr' messages. It's not a thing. See https://github.com/modelcontextprotocol/servers/pull/2469

* Inspect the stderr output of STDIO servers and attempt to assign an appropriate RFC 5424 Syslog Protocol level before sending a leveled logging message to the client

client/src/lib/hooks/useConnection.ts

@@ -36,7 +36,7 @@ import { useEffect, useState } from "react";
 import { useToast } from "@/lib/hooks/useToast";
 import { z } from "zod";
 import { ConnectionStatus } from "../constants";
-import { Notification, StdErrNotificationSchema } from "../notificationTypes";
+import { Notification } from "../notificationTypes";
 import {
   auth,
   discoverOAuthProtectedResourceMetadata,
@@ -92,7 +92,6 @@ export function useConnection({
   oauthScope,
   config,
   onNotification,
-  onStdErrNotification,
   onPendingRequest,
   onElicitationRequest,
   getRoots,
@@ -505,13 +504,6 @@ export function useConnection({
         };
       }
 
-      if (onStdErrNotification) {
-        client.setNotificationHandler(
-          StdErrNotificationSchema,
-          onStdErrNotification,
-        );
-      }
-
       let capabilities;
       try {
         const transport =