Calling firmware/install on an already-installed os-net-snmp plugin triggers an async reinstall that overwrites the config with factory defaults a few minutes later — causing SNMP to stop working again. Now checks /api/netsnmp/general/get first and only installs if the plugin is genuinely absent. Also adds a lightweight UDP/161 probe to verify SNMP is actually reachable after the fix (falls back to API config check if the socket probe is unavailable). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>