diff --git a/lightsync/frontend/app.js b/lightsync/frontend/app.js
index 19e211b..884d605 100644
--- a/lightsync/frontend/app.js
+++ b/lightsync/frontend/app.js
@@ -2,7 +2,7 @@
 // WebSocket stub + device list loader
 // Phase 2 expands audio, transport, and WS protocol
 
-const WS_URL = `ws://${location.host}/ws`;
+const WS_URL = `${location.protocol === 'https:' ? 'wss' : 'ws'}://${location.host}/ws`;
 
 async function apiPost(path, data) {
     const res = await fetch(path, {