NoClassDefFoundError occurs after running embed-server or jdr.sh alongside an active JBoss EAP 7.x/8.x server

Issue

• Application error such as NoClassDefFoundError happens on JBoss EAP 7.x/8.x after starting embed-server in JBoss-CLI (or executing $JBOSS_HOME/bin/jdr.sh) beside running server
• Starting embed-server (either directly via JBoss-CLI or indirectly via $JBOSS_HOME/bin/jdr.sh with incorrect connection details) while a JBoss EAP instance is running will delete the active server's tmp/vfs directory. This action removes critical class files, causing application failures with NoClassDefFoundError.
• Your application running on JBoss EAP unexpectedly fails with NoClassDefFoundError after you use the JBoss-CLI embed-server command or run the $JBOSS_HOME/bin/jdr.sh diagnostic script.