ppy/osu · error · InvalidOperationException

Cannot create a multiplayer room while already in one.

Error message

Cannot create a multiplayer room while already in one.

What it means

Thrown by MultiplayerClient.CreateRoom when the Room property is already non-null. The client models the user as being in at most one room at a time, so a second create is a logic error.

Source

Thrown at osu.Game/Online/Multiplayer/MultiplayerClient.cs:240

                        LeaveRoom().FireAndForget();

                    MatchmakingQueueLeft?.Invoke();
                }
            }));
        }

        private readonly TaskChain joinOrLeaveTaskChain = new TaskChain();
        private CancellationTokenSource? joinCancellationSource;

        /// <summary>
        /// Creates and joins a <see cref="MultiplayerRoom"/> described by an API <see cref="Room"/>.
        /// </summary>
        /// <param name="room">The API <see cref="Room"/> describing the room to create.</param>
        /// <exception cref="InvalidOperationException">If the current user is already in another room.</exception>
        public async Task CreateRoom(Room room)
        {
            if (Room != null)
                throw new InvalidOperationException("Cannot create a multiplayer room while already in one.");

            var cancellationSource = joinCancellationSource = new CancellationTokenSource();

            await joinOrLeaveTaskChain.Add(async () =>
            {
                await runOnUpdateThreadAsync(() => pendingRequests.Clear(), cancellationSource.Token).ConfigureAwait(false);
                var multiplayerRoom = await CreateRoomInternal(new MultiplayerRoom(room)).ConfigureAwait(false);
                await setupJoinedRoom(room, multiplayerRoom, cancellationSource.Token).ConfigureAwait(false);
            }, cancellationSource.Token).ConfigureAwait(false);
        }

        /// <summary>
        /// Joins the <see cref="MultiplayerRoom"/> for a given API <see cref="Room"/>.
        /// </summary>
        /// <param name="room">The API <see cref="Room"/>.</param>
        /// <param name="password">An optional password to use for the join operation.</param>
        /// <exception cref="InvalidOperationException">If the current user is already in another room, or <paramref name="room"/> does not represent an active room.</exception>
        public async Task JoinRoom(Room room, string? password = null)

View on GitHub (pinned to d9c73e12ad)

Solutions

1. Call LeaveRoom() (and await its completion) before invoking CreateRoom.
2. Guard the call: if (client.Room != null) await client.LeaveRoom().
3. Disable the create-room control while client.Room != null and re-enable only after LeaveRoom resolves.

Example fix

// before
await client.CreateRoom(room);

// after
if (client.Room != null)
    await client.LeaveRoom();
await client.CreateRoom(room);

if (client.Room != null)
    await client.LeaveRoom();
await client.CreateRoom(room);

try { await client.CreateRoom(room); }
catch (InvalidOperationException) { /* already in a room: leave then retry once */ }

When it happens

Trigger: Calling CreateRoom(room) while already joined to a room (Room != null) without first calling LeaveRoom(). Common in UI flows where the create button can be triggered twice or before a prior join fully tears down.

Common situations: Double-click on the create-room button; create invoked immediately after joining a room without leaving; stale room state after an unclean disconnect where Room was not cleared.

Related errors

• Cannot join a multiplayer room while already in one.
• Cannot join an inactive room.
• Must be joined to a match to change settings.
• Cannot toggle ready when in {localUser.State}
• Cannot toggle spectate when in {localUser.State}

AI-assisted analysis of ppy/osu@d9c73e12ad (2026-08-13). Data as JSON: /api/errors/5a4ce968b16adf5a. Report an issue: GitHub.