The packaged native app (Capacitor) serves the bundled SPA from a localhost scheme, so its Connect calls to erudit-game.ru are cross-origin. The gateway had no CORS handling, so the preflight OPTIONS returned 405 with no Access-Control-Allow-Origin and the WebView blocked every RPC — a native build could never reach the gateway and stayed stuck offline (the native online path was never exercised on-device; on-device D was airplane-mode only). Add a CORS middleware that answers the preflight and sets the response headers for the native localhost origins (https/http/capacitor://localhost); web is same-origin and untouched. Fixes the native emulator 'starts offline, can't go online' report.
Ilia Denisov