* 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/components/Sidebar.tsx

@@ -24,7 +24,6 @@ import {
   SelectTrigger,
   SelectValue,
 } from "@/components/ui/select";
-import { StdErrNotification } from "@/lib/notificationTypes";
 import {
   LoggingLevel,
   LoggingLevelSchema,
@@ -62,8 +61,6 @@ interface SidebarProps {
   setOauthScope: (scope: string) => void;
   onConnect: () => void;
   onDisconnect: () => void;
-  stdErrNotifications: StdErrNotification[];
-  clearStdErrNotifications: () => void;
   logLevel: LoggingLevel;
   sendLogLevelRequest: (level: LoggingLevel) => void;
   loggingSupported: boolean;
@@ -93,8 +90,6 @@ const Sidebar = ({
   setOauthScope,
   onConnect,
   onDisconnect,
-  stdErrNotifications,
-  clearStdErrNotifications,
   logLevel,
   sendLogLevelRequest,
   loggingSupported,
@@ -760,36 +755,6 @@ const Sidebar = ({
                 </Select>
               </div>
             )}
-
-            {stdErrNotifications.length > 0 && (
-              <>
-                <div className="mt-4 border-t border-gray-200 pt-4">
-                  <div className="flex justify-between items-center">
-                    <h3 className="text-sm font-medium">
-                      Error output from MCP server
-                    </h3>
-                    <Button
-                      variant="outline"
-                      size="sm"
-                      onClick={clearStdErrNotifications}
-                      className="h-8 px-2"
-                    >
-                      Clear
-                    </Button>
-                  </div>
-                  <div className="mt-2 max-h-80 overflow-y-auto">
-                    {stdErrNotifications.map((notification, index) => (
-                      <div
-                        key={index}
-                        className="text-sm text-red-500 font-mono py-2 border-b border-gray-200 last:border-b-0"
-                      >
-                        {notification.params.content}
-                      </div>
-                    ))}
-                  </div>
-                </div>
-              </>
-            )}
           </div>
         </div>
       </div>