diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7c78cd5..fff5e2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,10 +4,14 @@ All notable changes to the KoalaSync browser extension and relay server.
 
 ---
 
-## [v2.1.1] — 2026-06-04
+## [v2.1.2] — 2026-06-06
+
+### Fixed
+- **Episode guard regex**: Fixed `isDifferentEpisode()` not detecting episode changes when the MediaSession title uses `Sxx:Exx` format (colon separator, as used by Jellyfin/Emby). The regex character class `[\s\-\.]` was replaced with `[^a-zA-Z0-9]` to match **any** non-alphanumeric separator between season and episode numbers, preventing play/pause/seek commands from a different episode leaking through and incorrectly manipulating a peer's playback.
+- **Per-device storage isolation**: Migrated `username`, `roomId`, `password`, `serverUrl`, and `useCustomServer` from `chrome.storage.sync` (synced across Google account) to `chrome.storage.local` (per-device). This prevents the extension from automatically joining the same room with the same name on multiple devices. Existing user data is migrated silently on first run; all preferences (`filterNoise`, `autoSyncNextEpisode`, etc.) remain synced.
 
 ### Changed
-- Added progressive enhancement using `appearance: base-select` to support styling of country flag emojis in expanded language selectors on newer Chromium browsers.
+- Added one-time migration fallback in `getSettings()` and popup `init()` to copy existing user settings from `storage.sync` to `storage.local` on first launch after the update.
 
 ---
 
diff --git a/README.md b/README.md
index 16923e5..c12ceb3 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@
   <a href="https://chromewebstore.google.com/detail/koalasync/obbnmkmlaaddodakcbdljknjpagklifc"><img src="https://img.shields.io/badge/Chrome-Download-blue?logo=googlechrome&logoColor=white" alt="Chrome Extension"></a>
 </p>
 
-<p align="center"><a href="CHANGELOG.md"><b>New v2.1.1 Release!</b> — See what's changed</a></p>
+<p align="center"><a href="CHANGELOG.md"><b>New v2.1.2 Release!</b> — See what's changed</a></p>
 
 <p align="center"><i>KoalaSync is a lightweight Browser Extension and Relay Server for synchronized video playback on almost any website with a video element—YouTube, Twitch, Netflix, Emby, Jellyfin, and beyond. Built with a focus on <b>Data Sovereignty</b> and <b>Performance</b>.</i></p>
 
diff --git a/extension/background.js b/extension/background.js
index 46a4c33..1e372c1 100644
--- a/extension/background.js
+++ b/extension/background.js
@@ -230,35 +230,38 @@ async function getPeerId() {
 }
 
 async function getSettings() {
-    return new Promise((resolve, reject) => {
-        chrome.storage.sync.get(['serverUrl', 'useCustomServer', 'roomId', 'password', 'username'], (data) => {
-            if (chrome.runtime.lastError) {
-                reject(new Error(chrome.runtime.lastError.message));
-                return;
-            }
-            let username = data.username;
-            if (!username) {
-                username = generateUsername();
-                chrome.storage.sync.set({ username }, () => {
-                    resolve({
-                        serverUrl: data.serverUrl || '',
-                        useCustomServer: data.useCustomServer || false,
-                        roomId: data.roomId || '',
-                        password: data.password || '',
-                        username: username
-                    });
-                });
-            } else {
-                resolve({
-                    serverUrl: data.serverUrl || '',
-                    useCustomServer: data.useCustomServer || false,
-                    roomId: data.roomId || '',
-                    password: data.password || '',
-                    username: username
-                });
-            }
+    // Try local (per-device) first, fall back to sync for migration
+    let data = await chrome.storage.local.get(['serverUrl', 'useCustomServer', 'roomId', 'password', 'username']);
+    let migrated = false;
+    if (!data.username) {
+        const syncData = await chrome.storage.sync.get(['serverUrl', 'useCustomServer', 'roomId', 'password', 'username']);
+        if (syncData.username || syncData.roomId) {
+            data = syncData;
+            migrated = true;
+        }
+    }
+    let username = data.username;
+    if (!username) {
+        username = generateUsername();
+    }
+    if (migrated) {
+        await chrome.storage.local.set({ 
+            serverUrl: data.serverUrl || '',
+            useCustomServer: data.useCustomServer || false,
+            roomId: data.roomId || '',
+            password: data.password || '',
+            username
         });
-    });
+    } else if (!data.username) {
+        await chrome.storage.local.set({ username });
+    }
+    return {
+        serverUrl: data.serverUrl || '',
+        useCustomServer: data.useCustomServer || false,
+        roomId: data.roomId || '',
+        password: data.password || '',
+        username
+    };
 }
 
 function addLog(message, type = 'info') {
@@ -382,7 +385,7 @@ async function leaveRoomAfterIdleGrace(reason) {
         lastContentHeartbeatAt: null,
         episodeLobby: null
     }).catch(() => {});
-    await chrome.storage.sync.set({ roomId: '', password: '' }).catch(() => {});
+    await chrome.storage.local.set({ roomId: '', password: '' }).catch(() => {});
     addLog(reason, 'info');
     chrome.runtime.sendMessage({ type: 'PEER_UPDATE', peers: [] }).catch(() => {});
     updateBadgeStatus();
@@ -1396,7 +1399,7 @@ async function handleAsyncMessage(message, sender, sendResponse) {
     } else if (message.type === 'WEB_JOIN_REQUEST') {
         const { roomId: rawRoomId, password, useCustomServer, serverUrl } = message;
         const roomId = typeof rawRoomId === 'string' ? rawRoomId.replace(/[^a-zA-Z0-9\-]/g, '') : '';
-        chrome.storage.sync.set({ 
+        chrome.storage.local.set({ 
             roomId, 
             password,
             useCustomServer: !!useCustomServer,
diff --git a/extension/content.js b/extension/content.js
index 1d0824d..8ef655c 100644
--- a/extension/content.js
+++ b/extension/content.js
@@ -126,8 +126,8 @@
     // Returns null if no episode pattern found.
     function extractEpisodeId(title) {
         if (!title || typeof title !== 'string') return null;
-        // S01E01 patterns (with optional spaces, dashes, dots between S and E)
-        const se = title.match(/S(?:eason\s*)?(\d+)[\s\-\.]*E(?:pisode\s*)?(\d+)/i);
+        // S01E01 patterns (with any non-alphanumeric separator between season and E)
+        const se = title.match(/S(?:eason\s*)?(\d+)[^a-zA-Z0-9]*E(?:pisode\s*)?(\d+)/i);
         if (se) return `S${String(se[1]).padStart(2, '0')}E${String(se[2]).padStart(2, '0')}`;
         // "Episode X", "Folge X", "Ep. X", "#X"
         const ep = title.match(/(?:Episode|Folge|Ep\.?|#)\s*(\d+)/i);
diff --git a/extension/popup.js b/extension/popup.js
index 020fd0d..014452f 100644
--- a/extension/popup.js
+++ b/extension/popup.js
@@ -108,10 +108,28 @@ function setRoomRefreshCooldown() {
 
 // --- Initialization ---
 async function init() {
-    // Load Settings
-    const data = await chrome.storage.sync.get(['serverUrl', 'useCustomServer', 'roomId', 'password', 'filterNoise', 'username', 'autoSyncNextEpisode', 'forceSyncMode', 'browserNotifications', 'autoCopyInvite', 'locale']);
+    // Load per-device settings (local) + synced preferences (sync)
+    const [localData, syncData] = await Promise.all([
+        chrome.storage.local.get(['serverUrl', 'useCustomServer', 'roomId', 'password', 'username']),
+        chrome.storage.sync.get(['filterNoise', 'autoSyncNextEpisode', 'forceSyncMode', 'browserNotifications', 'autoCopyInvite', 'locale'])
+    ]);
 
-    let activeLang = data.locale;
+    // Migrate from sync → local for existing users
+    const hadLocalData = !!(localData.username || localData.roomId);
+    let syncHadData = false;
+    if (!hadLocalData) {
+        const oldSync = await chrome.storage.sync.get(['serverUrl', 'useCustomServer', 'roomId', 'password', 'username']);
+        syncHadData = !!(oldSync.username || oldSync.roomId);
+        if (syncHadData) {
+            localData.serverUrl = oldSync.serverUrl;
+            localData.useCustomServer = oldSync.useCustomServer;
+            localData.roomId = oldSync.roomId;
+            localData.password = oldSync.password;
+            localData.username = oldSync.username;
+        }
+    }
+
+    let activeLang = syncData.locale;
     if (!activeLang) {
         activeLang = getSystemLanguage();
         chrome.storage.sync.set({ locale: activeLang });
@@ -122,21 +140,31 @@ async function init() {
     
     if (elements.langSelector) elements.langSelector.value = activeLang;
     
-    let username = data.username;
+    let username = localData.username;
     if (!username) {
         username = generateUsername();
-        chrome.storage.sync.set({ username });
+        await chrome.storage.local.set({ username });
+    }
+    if (syncHadData) {
+        // Persist migrated room data to local (one-time migration)
+        await chrome.storage.local.set({
+            serverUrl: localData.serverUrl || '',
+            useCustomServer: localData.useCustomServer || false,
+            roomId: localData.roomId || '',
+            password: localData.password || '',
+            username
+        });
     }
     
-    elements.serverUrl.value = data.serverUrl || '';
-    elements.roomId.value = data.roomId || '';
-    elements.password.value = data.password || '';
+    elements.serverUrl.value = localData.serverUrl || '';
+    elements.roomId.value = localData.roomId || '';
+    elements.password.value = localData.password || '';
     elements.username.value = username;
-    if (elements.filterNoise) elements.filterNoise.checked = data.filterNoise !== false;
-    if (elements.autoSyncNextEpisode) elements.autoSyncNextEpisode.checked = data.autoSyncNextEpisode !== false;
-    if (elements.forceSyncMode) elements.forceSyncMode.value = data.forceSyncMode || 'jump-to-others';
-    if (elements.browserNotifications) elements.browserNotifications.checked = data.browserNotifications === true;
-    if (elements.autoCopyInvite) elements.autoCopyInvite.checked = data.autoCopyInvite !== false;
+    if (elements.filterNoise) elements.filterNoise.checked = syncData.filterNoise !== false;
+    if (elements.autoSyncNextEpisode) elements.autoSyncNextEpisode.checked = syncData.autoSyncNextEpisode !== false;
+    if (elements.forceSyncMode) elements.forceSyncMode.value = syncData.forceSyncMode || 'jump-to-others';
+    if (elements.browserNotifications) elements.browserNotifications.checked = syncData.browserNotifications === true;
+    if (elements.autoCopyInvite) elements.autoCopyInvite.checked = syncData.autoCopyInvite !== false;
     
     // Set Version Info
     const versionTxt = `v${chrome.runtime.getManifest().version}`;
@@ -145,14 +173,14 @@ async function init() {
     const popupVerEl = document.getElementById('popupVersion');
     if (popupVerEl) popupVerEl.textContent = versionTxt;
 
-    if (data.useCustomServer) {
+    if (localData.useCustomServer) {
         setServerMode(true);
     } else {
         setServerMode(false);
     }
 
-    toggleUIState(!!data.roomId);
-    updateUI(data.roomId, data.password, data.useCustomServer, data.serverUrl);
+    toggleUIState(!!localData.roomId);
+    updateUI(localData.roomId, localData.password, localData.useCustomServer, localData.serverUrl);
     refreshLogs();
     refreshHistory();
 
@@ -881,7 +909,7 @@ function checkInviteLink() {
                     if (serverUrl || useCustomServer) {
                         elements.serverUrl.value = serverUrl;
                         setServerMode(useCustomServer);
-                        chrome.storage.sync.set({ serverUrl, useCustomServer });
+                        chrome.storage.local.set({ serverUrl, useCustomServer });
                     }
 
                     elements.joinBtn.style.boxShadow = '0 0 15px var(--accent)';
@@ -898,9 +926,9 @@ function setServerMode(custom) {
     elements.serverOfficial.classList.toggle('active', !custom);
     elements.serverCustom.classList.toggle('active', custom);
     elements.serverUrl.style.display = custom ? 'block' : 'none';
-    chrome.storage.sync.get(['useCustomServer', 'serverUrl'], (data) => {
+    chrome.storage.local.get(['useCustomServer', 'serverUrl'], (data) => {
         if (data.useCustomServer !== custom) {
-            chrome.storage.sync.set({ useCustomServer: custom });
+            chrome.storage.local.set({ useCustomServer: custom });
             if (!custom || data.serverUrl) {
                 chrome.runtime.sendMessage({ type: 'RETRY_CONNECT' });
             }
@@ -936,11 +964,11 @@ elements.forceSyncMode.addEventListener('change', () => {
 });
 
 elements.serverUrl.addEventListener('input', () => {
-    chrome.storage.sync.set({ serverUrl: elements.serverUrl.value });
+    chrome.storage.local.set({ serverUrl: elements.serverUrl.value });
 });
 
 elements.username.addEventListener('change', () => {
-    chrome.storage.sync.set({ username: elements.username.value });
+    chrome.storage.local.set({ username: elements.username.value });
 });
 
 if (elements.langSelector) {
@@ -961,14 +989,14 @@ if (elements.langSelector) {
                 lastKnownPeers = res.peers || [];
                 if (res.lastActionState) updateLastActionUI(res.lastActionState, res.peers);
                 
-                const data = await chrome.storage.sync.get(['roomId', 'password', 'useCustomServer', 'serverUrl']);
+                const data = await chrome.storage.local.get(['roomId', 'password', 'useCustomServer', 'serverUrl']);
                 updateUI(data.roomId, data.password, data.useCustomServer, data.serverUrl);
                 
                 await populateTabs(res.peers, res.targetTabId);
                 if (res.episodeLobby) updateLobbyUI(res.episodeLobby, res.peers);
             } else {
                 applyConnectionStatus('disconnected');
-                const data = await chrome.storage.sync.get(['roomId', 'password', 'useCustomServer', 'serverUrl']);
+                const data = await chrome.storage.local.get(['roomId', 'password', 'useCustomServer', 'serverUrl']);
                 updateUI(data.roomId, data.password, data.useCustomServer, data.serverUrl);
                 await populateTabs();
             }
@@ -984,7 +1012,7 @@ elements.serverUrl.addEventListener('change', () => {
     if (url && !url.includes('://')) {
         url = 'ws://' + url;
         elements.serverUrl.value = url;
-        chrome.storage.sync.set({ serverUrl: url });
+        chrome.storage.local.set({ serverUrl: url });
     }
     if (elements.serverCustom.classList.contains('active') && url) {
         chrome.runtime.sendMessage({ type: 'RETRY_CONNECT' });
@@ -1098,7 +1126,7 @@ elements.joinBtn.addEventListener('click', async () => {
         window.justCreatedRoom = true;
     }
 
-    await chrome.storage.sync.set({ serverUrl, roomId, password, useCustomServer: useCustom });
+    await chrome.storage.local.set({ serverUrl, roomId, password, useCustomServer: useCustom });
     elements.roomId.value = roomId;
 
     // Tell background to connect
@@ -1111,7 +1139,7 @@ elements.joinBtn.addEventListener('click', async () => {
 elements.leaveBtn.addEventListener('click', async () => {
     clearConnectionErrorTimer();
     chrome.runtime.sendMessage({ type: 'LEAVE_ROOM' });
-    await chrome.storage.sync.set({ roomId: '', password: '' });
+    await chrome.storage.local.set({ roomId: '', password: '' });
     elements.roomId.value = '';
     elements.password.value = '';
     lastKnownPeers = [];
@@ -1501,7 +1529,7 @@ chrome.runtime.onMessage.addListener((msg) => {
 
         if (msg.success) {
             // Final confirmation of join from background
-            chrome.storage.sync.get(['roomId', 'password', 'useCustomServer', 'serverUrl'], (data) => {
+            chrome.storage.local.get(['roomId', 'password', 'useCustomServer', 'serverUrl'], (data) => {
                 updateUI(data.roomId, data.password, data.useCustomServer, data.serverUrl);
             });
         } else {
diff --git a/package.json b/package.json
index 6951526..2f2df48 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "koalasync",
-  "version": "2.1.1",
+  "version": "2.1.2",
   "description": "KoalaSync Build Scripts",
   "private": true,
   "scripts": {