diff --git a/lib/watch_together/services/watch_together_peer_service.dart b/lib/watch_together/services/watch_together_peer_service.dart
index c225d4ccf..c0d08e586 100644
--- a/lib/watch_together/services/watch_together_peer_service.dart
+++ b/lib/watch_together/services/watch_together_peer_service.dart
@@ -67,7 +67,7 @@ class WatchTogetherPeerService with KeepaliveMixin {
   final Set<String> _connectedPeers = {};
   String? _sessionId;
   String? _myPeerId;
-  bool _isHost = false;
+  bool _announcedAsHost = false;
   String? _reconnectToken;
   String? _hostPeerId;
 
@@ -135,7 +135,15 @@ class WatchTogetherPeerService with KeepaliveMixin {
   /// Relay-declared peer ID whose messages carry host authority.
   String? get hostPeerId => _hostPeerId;
 
-  /// Whether this peer is the host
+  /// Whether this peer is the host.
+  ///
+  /// Derived, never stored: the relay is the authority on host identity and
+  /// names it in every admission and every `hostChanged`. Before it has
+  /// admitted us there is no authority yet, so the role is the one we
+  /// announced — which is what a release of a possibly-committed setup has to
+  /// go by.
+  bool get _isHost => _hostPeerId == null ? _announcedAsHost : _hostPeerId == _myPeerId;
+
   bool get isHost => _isHost;
 
   /// Whether currently connected to a session
@@ -269,7 +277,7 @@ class WatchTogetherPeerService with KeepaliveMixin {
         responseSessionId != _sessionId ||
         hostPeerId is! String ||
         !RelayProtocol.isValidPeerId(hostPeerId) ||
-        (_isHost && hostPeerId != _myPeerId) ||
+        (type == RelayProtocol.created && hostPeerId != _myPeerId) ||
         reconnectToken is! String ||
         reconnectToken != _reconnectToken ||
         !RelayProtocol.isValidReconnectToken(reconnectToken) ||
@@ -453,7 +461,6 @@ class WatchTogetherPeerService with KeepaliveMixin {
           if (newHostPeerId == _hostPeerId) break; // Duplicate delivery.
           appLogger.d('WatchTogether: Host authority moved to $newHostPeerId');
           _hostPeerId = newHostPeerId;
-          _isHost = newHostPeerId == _myPeerId;
           _safeAdd(_hostChangedController, newHostPeerId);
 
         case RelayProtocol.error:
@@ -664,7 +671,7 @@ class WatchTogetherPeerService with KeepaliveMixin {
         'Must be 1–${RelayProtocol.maxSessionIdLength} letters, digits, _ or -',
       );
     }
-    _isHost = true;
+    _announcedAsHost = true;
     _sessionId = resolvedSessionId;
     _myPeerId = const Uuid().v4();
     _reconnectToken = _mintReconnectToken();
@@ -702,7 +709,7 @@ class WatchTogetherPeerService with KeepaliveMixin {
         'Must be 1–${RelayProtocol.maxSessionIdLength} letters, digits, _ or -',
       );
     }
-    _isHost = false;
+    _announcedAsHost = false;
     _sessionId = resolvedSessionId;
     _myPeerId = const Uuid().v4();
     _reconnectToken = _mintReconnectToken();
@@ -833,7 +840,7 @@ class WatchTogetherPeerService with KeepaliveMixin {
     _myPeerId = null;
     _reconnectToken = null;
     _hostPeerId = null;
-    _isHost = false;
+    _announcedAsHost = false;
     _reconnectAttempts = 0;
     _teardownInProgress = false;
 
diff --git a/test/watch_together/watch_together_peer_service_test.dart b/test/watch_together/watch_together_peer_service_test.dart
index c829a2c7a..00355f077 100644
--- a/test/watch_together/watch_together_peer_service_test.dart
+++ b/test/watch_together/watch_together_peer_service_test.dart
@@ -1337,4 +1337,113 @@ void main() {
     expect(service.isHost, isFalse);
     expect(errors, isEmpty);
   });
+
+  test('a demoted host reconnect adopts the authority the relay names', () async {
+    // The relay only broadcasts hostChanged to peers connected at the time, so
+    // a host that handed the room over and then dropped learns of its own
+    // demotion from its re-admission. Rejecting it locks the former host out
+    // of a room that is still running.
+    late final _RelayServer relay;
+    relay = await relayWith((connection, socket, message) {
+      if (connection == 0 && message['type'] == 'create') {
+        relay.send(socket, {
+          'type': 'created',
+          'sessionId': message['sessionId'],
+          'hostPeerId': message['peerId'],
+          'reconnectToken': message['reconnectToken'],
+          'protocolVersion': 2,
+        });
+      } else if (connection >= 1 && message['type'] == 'join') {
+        relay.send(socket, {
+          'type': 'joined',
+          'sessionId': message['sessionId'],
+          'hostPeerId': 'new-host',
+          'reconnectToken': message['reconnectToken'],
+          'protocolVersion': 2,
+          'peers': const ['new-host'],
+        });
+      }
+    });
+    final service = serviceFor(relay);
+    final errors = <PeerError>[];
+    final subscription = service.onError.listen(errors.add);
+    addTearDown(subscription.cancel);
+    final changed = Completer<String>();
+    final hostChanges = service.onHostChanged.listen((peerId) {
+      if (!changed.isCompleted) changed.complete(peerId);
+    });
+    addTearDown(hostChanges.cancel);
+    final reconnected = Completer<void>();
+    service.onReconnected = reconnected.complete;
+
+    await _withShortenedTimer(
+      original: const Duration(seconds: 2),
+      replacement: const Duration(milliseconds: 10),
+      body: () => service.createSession(sessionId: 'XFER9'),
+    );
+    await relay.sockets.single.close();
+    await reconnected.future.timeout(const Duration(seconds: 6));
+
+    expect(await changed.future.timeout(const Duration(seconds: 1)), 'new-host');
+    expect(service.hostPeerId, 'new-host');
+    expect(service.isHost, isFalse);
+    expect(errors, isEmpty);
+  });
+
+  test('a promotion learned from re-admission moves the transport role too', () async {
+    late final _RelayServer relay;
+    relay = await relayWith((connection, socket, message) {
+      switch (message['type']) {
+        case 'join':
+          relay.send(socket, {
+            'type': 'joined',
+            'sessionId': message['sessionId'],
+            // The reconnect: the relay made this peer the host while it was
+            // offline, so the hostChanged broadcast never reached it.
+            'hostPeerId': connection == 0 ? _relayHostId : message['peerId'],
+            'reconnectToken': message['reconnectToken'],
+            'protocolVersion': 2,
+            'peers': const ['other-guest'],
+          });
+        case 'endSession':
+          relay.send(socket, {
+            'type': 'ended',
+            'sessionId': message['sessionId'],
+            'peerId': message['peerId'],
+            'protocolVersion': 2,
+          });
+        case 'leave':
+          relay.send(socket, {
+            'type': 'left',
+            'sessionId': message['sessionId'],
+            'peerId': message['peerId'],
+            'protocolVersion': 2,
+          });
+      }
+    });
+    final service = serviceFor(relay);
+    final changed = Completer<String>();
+    final subscription = service.onHostChanged.listen((peerId) {
+      if (!changed.isCompleted) changed.complete(peerId);
+    });
+    addTearDown(subscription.cancel);
+    final reconnected = Completer<void>();
+    service.onReconnected = reconnected.complete;
+
+    await _withShortenedTimer(
+      original: const Duration(seconds: 2),
+      replacement: const Duration(milliseconds: 10),
+      body: () => service.joinSession('xfer8'),
+    );
+    await relay.sockets.single.close();
+    await reconnected.future.timeout(const Duration(seconds: 6));
+
+    expect(await changed.future.timeout(const Duration(seconds: 1)), service.myPeerId);
+    expect(service.isHost, isTrue);
+
+    // The role the relay declared is the one the transport acts on: a host
+    // destroys the room instead of quietly leaving it behind.
+    await service.releaseSession();
+    expect(relay.messages[1].map((message) => message['type']), ['join', 'endSession']);
+  });
 }