diff --git a/muxplex/frontend/terminal.js b/muxplex/frontend/terminal.js
index 3fc4109..ba50478 100644
--- a/muxplex/frontend/terminal.js
+++ b/muxplex/frontend/terminal.js
@@ -661,20 +661,32 @@ function switchTerminal(sessionName, remoteId, fontSize) {
     }
   }
 
-  // 3. If target is in cache — instant switch, no network
+  // 3. If target is in cache — check WebSocket liveness before the fast path
   if (_terminalCache.has(key)) {
     var entry = _terminalCache.get(key);
-    if (entry.container) {
-      entry.container.style.display = '';
+    var wsIsLive = entry.ws &&
+                   (entry.ws.readyState === WebSocket.OPEN ||
+                    entry.ws.readyState === WebSocket.CONNECTING);
+    if (wsIsLive) {
+      // Fast path: live connection — swap containers, no network round-trip
+      if (entry.container) {
+        entry.container.style.display = '';
+      }
+      _syncModuleState(entry);
+      _activeSessionKey = key;
+      _touchCacheOrder(key);
+      if (_fitAddon) {
+        try { _fitAddon.fit(); } catch (_) {}
+      }
+      if (_term) _term.focus();
+      return;
     }
-    _syncModuleState(entry);
-    _activeSessionKey = key;
-    _touchCacheOrder(key);
-    if (_fitAddon) {
-      try { _fitAddon.fit(); } catch (_) {}
-    }
-    if (_term) _term.focus();
-    return;
+    // WebSocket died while this session was in the background.
+    // The close handler's stale-guard (ws !== _ws) suppresses reconnects for
+    // non-active sessions, so the entry is left with a dead socket.
+    // Destroy the stale entry and fall through to create a fresh terminal.
+    // openSession() already POST'd /connect so the backend ttyd is ready.
+    destroyCachedEntry(key);
   }
 
   // 4. Not in cache — create new entry
@@ -698,7 +710,12 @@ function switchTerminal(sessionName, remoteId, fontSize) {
   subContainer.style.height = '100%';
   parentContainer.appendChild(subContainer);
 
-  // Reset module-level state for fresh creation
+  // Reset module-level state for fresh creation.
+  // Null _term/_fitAddon BEFORE createTerminal() so it does NOT dispose the
+  // previously-active session's terminal — that terminal lives on in its own
+  // cache entry and must stay alive for instant switching later.
+  _term = null;
+  _fitAddon = null;
   _currentSession = null;
   _reconnectAttempts = 0;
   _reconnectTimer = null;