Notify users of who is spectating them

SampleMultiplayerClient/SampleMultiplayerClient.csproj

@@ -11,7 +11,7 @@
         <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.MessagePack" Version="9.0.0" />
         <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.0" />
         <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.0" />
-        <PackageReference Include="ppy.osu.Game" Version="2025.114.0" />
+        <PackageReference Include="ppy.osu.Game" Version="2025.122.0" />
     </ItemGroup>
 
 </Project>

SampleSpectatorClient/SampleSpectatorClient.csproj

@@ -11,7 +11,7 @@
         <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.MessagePack" Version="9.0.0" />
         <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.0" />
         <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.0" />
-        <PackageReference Include="ppy.osu.Game" Version="2025.114.0" />
+        <PackageReference Include="ppy.osu.Game" Version="2025.122.0" />
     </ItemGroup>
 
 </Project>

SampleSpectatorClient/SpectatorClient.cs

@@ -64,6 +64,19 @@ Task ISpectatorClient.UserScoreProcessed(int userId, long scoreId)
             return Task.CompletedTask;
         }
 
+        Task ISpectatorClient.UserStartedWatching(SpectatorUser[] users)
+        {
+            foreach (var user in users)
+                Console.WriteLine($"{connection.ConnectionId} User {user.OnlineID} started watching you");
+            return Task.CompletedTask;
+        }
+
+        Task ISpectatorClient.UserEndedWatching(int userId)
+        {
+            Console.WriteLine($"{connection.ConnectionId} User {userId} ended watching you");
+            return Task.CompletedTask;
+        }
+
         public Task BeginPlaying(long? scoreToken, SpectatorState state) => connection.SendAsync(nameof(ISpectatorServer.BeginPlaySession), scoreToken, state);
 
         public Task SendFrames(FrameDataBundle data) => connection.SendAsync(nameof(ISpectatorServer.SendFrameData), data);

osu.Server.Spectator.Tests/SpectatorHubTest.cs

@@ -10,7 +10,6 @@
 using Moq;
 using osu.Game.Beatmaps;
 using osu.Game.Online.API;
-using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Online.Spectator;
 using osu.Game.Replays.Legacy;
 using osu.Game.Rulesets.Osu.Mods;
@@ -325,9 +324,12 @@ public async Task NewUserBeginsWatchingStream(bool ongoing)
 
             Mock<IHubCallerClients<ISpectatorClient>> mockClients = new Mock<IHubCallerClients<ISpectatorClient>>();
             Mock<ISpectatorClient> mockCaller = new Mock<ISpectatorClient>();
+            Mock<ISpectatorClient> mockStreamer = new Mock<ISpectatorClient>();
 
             mockClients.Setup(clients => clients.Caller).Returns(mockCaller.Object);
             mockClients.Setup(clients => clients.All).Returns(mockCaller.Object);
+            mockClients.Setup(clients => clients.User(streamer_id.ToString())).Returns(mockStreamer.Object);
+            mockDatabase.Setup(db => db.GetUsernameAsync(watcher_id)).ReturnsAsync("watcher");
 
             Mock<IGroupManager> mockGroups = new Mock<IGroupManager>();
 
@@ -362,6 +364,12 @@ public async Task NewUserBeginsWatchingStream(bool ongoing)
             mockGroups.Verify(groups => groups.AddToGroupAsync(connectionId, SpectatorHub.GetGroupId(streamer_id), default));
 
             mockCaller.Verify(clients => clients.UserBeganPlaying(streamer_id, It.Is<SpectatorState>(m => m.Equals(state))), Times.Exactly(ongoing ? 2 : 0));
+            mockStreamer.Verify(client => client.UserStartedWatching(It.Is<SpectatorUser[]>(users => users.Single().OnlineID == watcher_id)), Times.Once);
+
+            await hub.EndWatchingUser(streamer_id);
+
+            mockGroups.Verify(groups => groups.RemoveFromGroupAsync(connectionId, SpectatorHub.GetGroupId(streamer_id), default));
+            mockStreamer.Verify(client => client.UserEndedWatching(watcher_id), Times.Once);
         }
 
         [Fact]

osu.Server.Spectator/Hubs/Spectator/SpectatorClientState.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using Newtonsoft.Json;
 using osu.Game.Online.Spectator;
 using osu.Game.Scoring;
@@ -11,12 +12,26 @@ namespace osu.Server.Spectator.Hubs.Spectator
     [Serializable]
     public class SpectatorClientState : ClientState
     {
+        /// <summary>
+        /// When a user is in gameplay, this is the state as conveyed at the start of the play session.
+        /// </summary>
         public SpectatorState? State;
 
+        /// <summary>
+        /// When a user is in gameplay, this is the imminent score. It will be updated throughout a play session.
+        /// </summary>
         public Score? Score;
 
+        /// <summary>
+        /// The score token as conveyed by the client at the beginning of a play session.
+        /// </summary>
         public long? ScoreToken;
 
+        /// <summary>
+        /// The list of IDs of users that this client is currently watching.
+        /// </summary>
+        public HashSet<int> WatchedUsers = new HashSet<int>();
+
         [JsonConstructor]
         public SpectatorClientState(in string connectionId, in int userId)
             : base(connectionId, userId)

osu.Server.Spectator/Hubs/Spectator/SpectatorHub.cs

@@ -154,7 +154,12 @@ public async Task EndPlaySession(SpectatorState state)
                 }
                 finally
                 {
-                    usage.Destroy();
+                    if (usage.Item != null)
+                    {
+                        usage.Item.State = null;
+                        usage.Item.Score = null;
+                        usage.Item.ScoreToken = null;
+                    }
                 }
             }
 
@@ -202,12 +207,44 @@ public async Task StartWatchingUser(int userId)
                 // user isn't tracked.
             }
 
+            using (var state = await GetOrCreateLocalUserState())
+            {
+                var clientState = state.Item ??= new SpectatorClientState(Context.ConnectionId, Context.GetUserId());
+                clientState.WatchedUsers.Add(userId);
+            }
+
             await Groups.AddToGroupAsync(Context.ConnectionId, GetGroupId(userId));
+
+            int watcherId = Context.GetUserId();
+            string? watcherUsername;
+            using (var db = databaseFactory.GetInstance())
+                watcherUsername = await db.GetUsernameAsync(watcherId);
+
+            if (watcherUsername == null)
+                return;
+
+            var watcher = new SpectatorUser
+            {
+                OnlineID = watcherId,
+                Username = watcherUsername,
+            };
+
+            await Clients.User(userId.ToString()).UserStartedWatching([watcher]);
         }
 
         public async Task EndWatchingUser(int userId)
         {
             await Groups.RemoveFromGroupAsync(Context.ConnectionId, GetGroupId(userId));
+
+            using (var state = await GetOrCreateLocalUserState())
+            {
+                var clientState = state.Item ??= new SpectatorClientState(Context.ConnectionId, Context.GetUserId());
+                clientState.WatchedUsers.Remove(userId);
+            }
+
+            int watcherId = Context.GetUserId();
+
+            await Clients.User(userId.ToString()).UserEndedWatching(watcherId);
         }
 
         public override async Task OnConnectedAsync()
@@ -225,6 +262,9 @@ protected override async Task CleanUpState(SpectatorClientState state)
             if (state.State != null)
                 await endPlaySession(state.UserId, state.State);
 
+            foreach (int watchedUserId in state.WatchedUsers)
+                await Clients.User(watchedUserId.ToString()).UserEndedWatching(state.UserId);
+
             await base.CleanUpState(state);
         }
 

osu.Server.Spectator/osu.Server.Spectator.csproj

@@ -15,11 +15,11 @@
         <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.0" />
         <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="8.0.10" />
         <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="8.0.1" />
-        <PackageReference Include="ppy.osu.Game" Version="2025.114.0" />
-        <PackageReference Include="ppy.osu.Game.Rulesets.Catch" Version="2025.114.0" />
-        <PackageReference Include="ppy.osu.Game.Rulesets.Mania" Version="2025.114.0" />
-        <PackageReference Include="ppy.osu.Game.Rulesets.Osu" Version="2025.114.0" />
-        <PackageReference Include="ppy.osu.Game.Rulesets.Taiko" Version="2025.114.0" />
+        <PackageReference Include="ppy.osu.Game" Version="2025.122.0" />
+        <PackageReference Include="ppy.osu.Game.Rulesets.Catch" Version="2025.122.0" />
+        <PackageReference Include="ppy.osu.Game.Rulesets.Mania" Version="2025.122.0" />
+        <PackageReference Include="ppy.osu.Game.Rulesets.Osu" Version="2025.122.0" />
+        <PackageReference Include="ppy.osu.Game.Rulesets.Taiko" Version="2025.122.0" />
         <PackageReference Include="ppy.osu.Server.OsuQueueProcessor" Version="2024.507.0" />
         <PackageReference Include="Sentry.AspNetCore" Version="5.0.1" />
     </ItemGroup>