Content update for UI prediction (#27214)

* Content update for UI refactor

* Big update

* Sharing

* Remaining content updates

* First big update

* Prototype updates

* AUGH

* Fix UI comp ref

* Cleanup

- Fix predicted message, fix item slots, fix interaction range check.

* Fix regressions

* Make this predictive

idk why it wasn't.

* Fix slime merge

* Merge conflict

* Fix merge

Content.Client/Administration/Components/HeadstandComponent.cs

@@ -3,7 +3,7 @@ using Robust.Shared.GameStates;
 
 namespace Content.Client.Administration.Components;
 
-[RegisterComponent, NetworkedComponent]
+[RegisterComponent]
 public sealed partial class HeadstandComponent : SharedHeadstandComponent
 {
 

Content.Client/Administration/Components/KillSignComponent.cs

@@ -3,6 +3,5 @@ using Robust.Shared.GameStates;
 
 namespace Content.Client.Administration.Components;
 
-[NetworkedComponent, RegisterComponent]
+[RegisterComponent]
-public sealed partial class KillSignComponent : SharedKillSignComponent
+public sealed partial class KillSignComponent : SharedKillSignComponent;
-{ }

Content.Client/Audio/Jukebox/JukeboxSystem.cs

@@ -11,6 +11,7 @@ public sealed class JukeboxSystem : SharedJukeboxSystem
     [Dependency] private readonly IPrototypeManager _protoManager = default!;
     [Dependency] private readonly AnimationPlayerSystem _animationPlayer = default!;
     [Dependency] private readonly SharedAppearanceSystem _appearanceSystem = default!;
+    [Dependency] private readonly SharedUserInterfaceSystem _uiSystem = default!;
 
     public override void Initialize()
     {
@@ -35,13 +36,10 @@ public sealed class JukeboxSystem : SharedJukeboxSystem
 
         var query = AllEntityQuery<JukeboxComponent, UserInterfaceComponent>();
 
-        while (query.MoveNext(out _, out var ui))
+        while (query.MoveNext(out var uid, out _, out var ui))
         {
-            if (!ui.OpenInterfaces.TryGetValue(JukeboxUiKey.Key, out var baseBui) ||
+            if (!_uiSystem.TryGetOpenUi<JukeboxBoundUserInterface>((uid, ui), JukeboxUiKey.Key, out var bui))
-                baseBui is not JukeboxBoundUserInterface bui)
-            {
                 continue;
-            }
 
             bui.PopulateMusic();
         }
@@ -49,15 +47,9 @@ public sealed class JukeboxSystem : SharedJukeboxSystem
 
     private void OnJukeboxAfterState(Entity<JukeboxComponent> ent, ref AfterAutoHandleStateEvent args)
     {
-        if (!TryComp(ent, out UserInterfaceComponent? ui))
+        if (!_uiSystem.TryGetOpenUi<JukeboxBoundUserInterface>(ent.Owner, JukeboxUiKey.Key, out var bui))
             return;
 
-        if (!ui.OpenInterfaces.TryGetValue(JukeboxUiKey.Key, out var baseBui) ||
-            baseBui is not JukeboxBoundUserInterface bui)
-        {
-            return;
-        }
-
         bui.Reload();
     }
 

Content.Client/Extinguisher/FireExtinguisherComponent.cs

@@ -3,7 +3,5 @@ using Robust.Shared.GameStates;
 
 namespace Content.Client.Extinguisher;
 
-[NetworkedComponent, RegisterComponent]
+[RegisterComponent]
-public sealed partial class FireExtinguisherComponent : SharedFireExtinguisherComponent
+public sealed partial class FireExtinguisherComponent : SharedFireExtinguisherComponent;
-{
-}

Content.Client/PDA/PdaBoundUserInterface.cs

@@ -21,7 +21,6 @@ namespace Content.Client.PDA
         protected override void Open()
         {
             base.Open();
-            SendMessage(new PdaRequestUpdateInterfaceMessage());
             _menu = new PdaMenu();
             _menu.OpenCenteredLeft();
             _menu.OnClose += Close;
@@ -32,17 +31,17 @@ namespace Content.Client.PDA
 
             _menu.EjectIdButton.OnPressed += _ =>
             {
-                SendMessage(new ItemSlotButtonPressedEvent(PdaComponent.PdaIdSlotId));
+                SendPredictedMessage(new ItemSlotButtonPressedEvent(PdaComponent.PdaIdSlotId));
             };
 
             _menu.EjectPenButton.OnPressed += _ =>
             {
-                SendMessage(new ItemSlotButtonPressedEvent(PdaComponent.PdaPenSlotId));
+                SendPredictedMessage(new ItemSlotButtonPressedEvent(PdaComponent.PdaPenSlotId));
             };
 
             _menu.EjectPaiButton.OnPressed += _ =>
             {
-                SendMessage(new ItemSlotButtonPressedEvent(PdaComponent.PdaPaiSlotId));
+                SendPredictedMessage(new ItemSlotButtonPressedEvent(PdaComponent.PdaPaiSlotId));
             };
 
             _menu.ActivateMusicButton.OnPressed += _ =>

Content.Client/Paper/PaperComponent.cs

@@ -1,9 +1,6 @@
 using Content.Shared.Paper;
-using Robust.Shared.GameStates;
 
 namespace Content.Client.Paper;
 
-[NetworkedComponent, RegisterComponent]
+[RegisterComponent]
-public sealed partial class PaperComponent : SharedPaperComponent
+public sealed partial class PaperComponent : SharedPaperComponent;
-{
-}

Content.Client/Power/ActivatableUIRequiresPowerSystem.cs

@@ -0,0 +1,21 @@
+using Content.Shared.Power.Components;
+using Content.Shared.UserInterface;
+using Content.Shared.Wires;
+
+namespace Content.Client.Power;
+
+public sealed class ActivatableUIRequiresPowerSystem : EntitySystem
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<ActivatableUIRequiresPowerComponent, ActivatableUIOpenAttemptEvent>(OnActivate);
+    }
+
+    private void OnActivate(EntityUid uid, ActivatableUIRequiresPowerComponent component, ActivatableUIOpenAttemptEvent args)
+    {
+        // Client can't predict the power properly at the moment so rely upon the server to do it.
+        args.Cancel();
+    }
+}

Content.Client/Storage/StorageBoundUserInterface.cs

@@ -17,6 +17,14 @@ public sealed class StorageBoundUserInterface : BoundUserInterface
         _storage = _entManager.System<StorageSystem>();
     }
 
+    protected override void Open()
+    {
+        base.Open();
+
+        if (_entManager.TryGetComponent<StorageComponent>(Owner, out var comp))
+            _storage.OpenStorageWindow((Owner, comp));
+    }
+
     protected override void Dispose(bool disposing)
     {
         base.Dispose(disposing);
@@ -25,16 +33,5 @@ public sealed class StorageBoundUserInterface : BoundUserInterface
 
         _storage.CloseStorageWindow(Owner);
     }
-
-    protected override void ReceiveMessage(BoundUserInterfaceMessage message)
-    {
-        base.ReceiveMessage(message);
-
-        if (message is StorageModifyWindowMessage)
-        {
-            if (_entManager.TryGetComponent<StorageComponent>(Owner, out var comp))
-                _storage.OpenStorageWindow((Owner, comp));
-        }
-    }
 }
 

Content.Client/Storage/Systems/StorageSystem.cs

@@ -111,7 +111,7 @@ public sealed class StorageSystem : SharedStorageSystem
         if (!Resolve(entity, ref entity.Comp, false))
             return;
 
-        if (entity.Comp.OpenInterfaces.GetValueOrDefault(StorageComponent.StorageUiKey.Key) is not { } bui)
+        if (entity.Comp.ClientOpenInterfaces.GetValueOrDefault(StorageComponent.StorageUiKey.Key) is not { } bui)
             return;
 
         bui.Close();

Content.Client/Strip/StrippableSystem.cs

@@ -35,7 +35,7 @@ public sealed class StrippableSystem : SharedStrippableSystem
         if (!TryComp(uid, out UserInterfaceComponent? uiComp))
             return;
 
-        foreach (var ui in uiComp.OpenInterfaces.Values)
+        foreach (var ui in uiComp.ClientOpenInterfaces.Values)
         {
             if (ui is StrippableBoundUserInterface stripUi)
                 stripUi.DirtyMenu();

Content.Client/UserInterface/Systems/Storage/StorageUIController.cs

@@ -262,7 +262,7 @@ public sealed class StorageUIController : UIController, IOnSystemChanged<Storage
         }
         else if (args.Function == ContentKeyFunctions.ActivateItemInWorld)
         {
-            _entity.EntityNetManager?.SendSystemNetworkMessage(
+            _entity.RaisePredictiveEvent(
                 new InteractInventorySlotEvent(_entity.GetNetEntity(control.Entity), altInteract: false));
             args.Handle();
         }

Content.IntegrationTests/Tests/Interaction/InteractionTest.Helpers.cs

@@ -820,7 +820,7 @@ public abstract partial class InteractionTest
             return false;
         }
 
-        if (!ui.OpenInterfaces.TryGetValue(key, out bui))
+        if (!ui.ClientOpenInterfaces.TryGetValue(key, out bui))
         {
             if (shouldSucceed)
                 Assert.Fail($"Entity {SEntMan.ToPrettyString(SEntMan.GetEntity(target.Value))} does not have an open bui with key {key.GetType()}.{key}.");

Content.IntegrationTests/Tests/Power/PowerTest.cs

@@ -143,8 +143,8 @@ namespace Content.IntegrationTests.Tests.Power
     anchored: true
   - type: UserInterface
     interfaces:
-    - key: enum.ApcUiKey.Key
+      enum.ApcUiKey.Key:
-      type: ApcBoundUserInterface
+        type: ApcBoundUserInterface
   - type: AccessReader
     access: [['Engineering']]
 

Content.Server/Access/Systems/AccessOverriderSystem.cs

@@ -68,16 +68,13 @@ public sealed class AccessOverriderSystem : SharedAccessOverriderSystem
 
     private void OnDoAfter(EntityUid uid, AccessOverriderComponent component, AccessOverriderDoAfterEvent args)
     {
-        if (!TryComp(args.User, out ActorComponent? actor))
-            return;
-
         if (args.Handled || args.Cancelled)
             return;
 
         if (args.Args.Target != null)
         {
             component.TargetAccessReaderId = args.Args.Target.Value;
-            _userInterface.TryOpen(uid, AccessOverriderUiKey.Key, actor.PlayerSession);
+            _userInterface.OpenUi(uid, AccessOverriderUiKey.Key, args.User);
             UpdateUserInterface(uid, component, args);
         }
 
@@ -94,7 +91,7 @@ public sealed class AccessOverriderSystem : SharedAccessOverriderSystem
 
     private void OnWriteToTargetAccessReaderIdMessage(EntityUid uid, AccessOverriderComponent component, WriteToTargetAccessReaderIdMessage args)
     {
-        if (args.Session.AttachedEntity is not { Valid: true } player)
+        if (args.Actor is not { Valid: true } player)
             return;
 
         TryWriteToTargetAccessReaderId(uid, args.AccessList, player, component);
@@ -154,22 +151,19 @@ public sealed class AccessOverriderSystem : SharedAccessOverriderSystem
             targetLabel,
             targetLabelColor);
 
-        _userInterface.TrySetUiState(uid, AccessOverriderUiKey.Key, newState);
+        _userInterface.SetUiState(uid, AccessOverriderUiKey.Key, newState);
     }
 
     private List<ProtoId<AccessLevelPrototype>> ConvertAccessHashSetsToList(List<HashSet<ProtoId<AccessLevelPrototype>>> accessHashsets)
     {
-        List<ProtoId<AccessLevelPrototype>> accessList = new List<ProtoId<AccessLevelPrototype>>();
+        var accessList = new List<ProtoId<AccessLevelPrototype>>();
 
-        if (accessHashsets != null && accessHashsets.Any())
+        if (accessHashsets.Count <= 0)
+            return accessList;
+
+        foreach (var hashSet in accessHashsets)
         {
-            foreach (HashSet<ProtoId<AccessLevelPrototype>> hashSet in accessHashsets)
+            accessList.AddRange(hashSet);
-            {
-                foreach (ProtoId<AccessLevelPrototype> hash in hashSet.ToArray())
-                {
-                    accessList.Add(hash);
-                }
-            }
         }
 
         return accessList;

Content.Server/Access/Systems/AgentIDCardSystem.cs

@@ -61,14 +61,14 @@ namespace Content.Server.Access.Systems
 
         private void AfterUIOpen(EntityUid uid, AgentIDCardComponent component, AfterActivatableUIOpenEvent args)
         {
-            if (!_uiSystem.TryGetUi(uid, AgentIDCardUiKey.Key, out var ui))
+            if (!_uiSystem.HasUi(uid, AgentIDCardUiKey.Key))
                 return;
 
             if (!TryComp<IdCardComponent>(uid, out var idCard))
                 return;
 
             var state = new AgentIDCardBoundUserInterfaceState(idCard.FullName ?? "", idCard.JobTitle ?? "", component.Icons);
-            _uiSystem.SetUiState(ui, state, args.Session);
+            _uiSystem.SetUiState(uid, AgentIDCardUiKey.Key, state);
         }
 
         private void OnJobChanged(EntityUid uid, AgentIDCardComponent comp, AgentIDCardJobChangedMessage args)

Content.Server/Access/Systems/IdCardConsoleSystem.cs

@@ -41,7 +41,7 @@ public sealed class IdCardConsoleSystem : SharedIdCardConsoleSystem
 
     private void OnWriteToTargetIdMessage(EntityUid uid, IdCardConsoleComponent component, WriteToTargetIdMessage args)
     {
-        if (args.Session.AttachedEntity is not { Valid: true } player)
+        if (args.Actor is not { Valid: true } player)
             return;
 
         TryWriteToTargetId(uid, args.FullName, args.JobTitle, args.AccessList, args.JobPrototype, player, component);
@@ -104,7 +104,7 @@ public sealed class IdCardConsoleSystem : SharedIdCardConsoleSystem
                 Name(targetId));
         }
 
-        _userInterface.TrySetUiState(uid, IdCardConsoleUiKey.Key, newState);
+        _userInterface.SetUiState(uid, IdCardConsoleUiKey.Key, newState);
     }
 
     /// <summary>

Content.Server/Administration/Components/HeadstandComponent.cs

@@ -3,7 +3,7 @@ using Robust.Shared.GameStates;
 
 namespace Content.Server.Administration.Components;
 
-[RegisterComponent, NetworkedComponent]
+[RegisterComponent]
 public sealed partial class HeadstandComponent : SharedHeadstandComponent
 {
 

Content.Server/Administration/Components/KillSignComponent.cs

@@ -3,6 +3,5 @@ using Robust.Shared.GameStates;
 
 namespace Content.Server.Administration.Components;
 
-[NetworkedComponent, RegisterComponent]
+[RegisterComponent]
-public sealed partial class KillSignComponent : SharedKillSignComponent
+public sealed partial class KillSignComponent : SharedKillSignComponent;
-{ }

Content.Server/Administration/Systems/AdminVerbSystem.cs

@@ -463,7 +463,7 @@ namespace Content.Server.Administration.Systems
                     Text = Loc.GetString("configure-verb-get-data-text"),
                     Icon = new SpriteSpecifier.Texture(new ("/Textures/Interface/VerbIcons/settings.svg.192dpi.png")),
                     Category = VerbCategory.Debug,
-                    Act = () => _uiSystem.TryOpen(args.Target, ConfigurationUiKey.Key, actor.PlayerSession)
+                    Act = () => _uiSystem.OpenUi(args.Target, ConfigurationUiKey.Key, actor.PlayerSession)
                 };
                 args.Verbs.Add(verb);
             }

Content.Server/Advertise/EntitySystems/SpeakOnUIClosedSystem.cs

@@ -4,6 +4,7 @@ using Content.Server.UserInterface;
 using Content.Shared.Advertise;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Random;
+using ActivatableUIComponent = Content.Shared.UserInterface.ActivatableUIComponent;
 
 namespace Content.Server.Advertise;
 

Content.Server/Ame/EntitySystems/AmeControllerSystem.cs

@@ -129,11 +129,11 @@ public sealed class AmeControllerSystem : EntitySystem
         if (!Resolve(uid, ref controller))
             return;
 
-        if (!_userInterfaceSystem.TryGetUi(uid, AmeControllerUiKey.Key, out var bui))
+        if (!_userInterfaceSystem.HasUi(uid, AmeControllerUiKey.Key))
             return;
 
         var state = GetUiState(uid, controller);
-        _userInterfaceSystem.SetUiState(bui, state);
+        _userInterfaceSystem.SetUiState(uid, AmeControllerUiKey.Key, state);
 
         controller.NextUIUpdate = _gameTiming.CurTime + controller.UpdateUIPeriod;
     }
@@ -324,7 +324,7 @@ public sealed class AmeControllerSystem : EntitySystem
 
     private void OnUiButtonPressed(EntityUid uid, AmeControllerComponent comp, UiButtonPressedMessage msg)
     {
-        var user = msg.Session.AttachedEntity;
+        var user = msg.Actor;
         if (!Exists(user))
             return;
 
@@ -334,7 +334,7 @@ public sealed class AmeControllerSystem : EntitySystem
             _ => true,
         };
 
-        if (!PlayerCanUseController(uid, user!.Value, needsPower, comp))
+        if (!PlayerCanUseController(uid, user, needsPower, comp))
             return;
 
         _audioSystem.PlayPvs(comp.ClickSound, uid, AudioParams.Default.WithVolume(-2f));

Content.Server/Anomaly/AnomalySystem.Generator.cs

@@ -61,7 +61,7 @@ public sealed partial class AnomalySystem
         var materialAmount = _material.GetMaterialAmount(uid, component.RequiredMaterial);
 
         var state = new AnomalyGeneratorUserInterfaceState(component.CooldownEndTime, materialAmount, component.MaterialPerAnomaly);
-        _ui.TrySetUiState(uid, AnomalyGeneratorUiKey.Key, state);
+        _ui.SetUiState(uid, AnomalyGeneratorUiKey.Key, state);
     }
 
     public void TryGeneratorCreateAnomaly(EntityUid uid, AnomalyGeneratorComponent? component = null)

Content.Server/Anomaly/AnomalySystem.Scanner.cs

@@ -31,7 +31,8 @@ public sealed partial class AnomalySystem
         {
             if (component.ScannedAnomaly != args.Anomaly)
                 continue;
-            _ui.TryCloseAll(uid, AnomalyScannerUiKey.Key);
+
+            _ui.CloseUi(uid, AnomalyScannerUiKey.Key);
         }
     }
 
@@ -108,7 +109,7 @@ public sealed partial class AnomalySystem
         Popup.PopupEntity(Loc.GetString("anomaly-scanner-component-scan-complete"), uid);
         UpdateScannerWithNewAnomaly(uid, args.Args.Target.Value, component);
 
-        if (TryComp<ActorComponent>(args.Args.User, out var actor)) _ui.TryOpen(uid, AnomalyScannerUiKey.Key, actor.PlayerSession);
+        _ui.OpenUi(uid, AnomalyScannerUiKey.Key, args.User);
 
         args.Handled = true;
     }
@@ -123,7 +124,7 @@ public sealed partial class AnomalySystem
             nextPulse = anomalyComponent.NextPulseTime;
 
         var state = new AnomalyScannerUserInterfaceState(GetScannerMessage(component), nextPulse);
-        _ui.TrySetUiState(uid, AnomalyScannerUiKey.Key, state);
+        _ui.SetUiState(uid, AnomalyScannerUiKey.Key, state);
     }
 
     public void UpdateScannerWithNewAnomaly(EntityUid scanner, EntityUid anomaly, AnomalyScannerComponent? scannerComp = null, AnomalyComponent? anomalyComp = null)

Content.Server/Arcade/BlockGame/BlockGame.Ui.cs

@@ -157,39 +157,37 @@ public sealed partial class BlockGame
     /// <param name="message">The message to broadcase to all players/spectators.</param>
     private void SendMessage(BoundUserInterfaceMessage message)
     {
-        if (_uiSystem.TryGetUi(_owner, BlockGameUiKey.Key, out var bui))
+        _uiSystem.ServerSendUiMessage(_entityManager.GetEntity(message.Entity), BlockGameUiKey.Key, message);
-            _uiSystem.SendUiMessage(bui, message);
     }
 
     /// <summary>
     /// Handles sending a message to a specific player/spectator.
     /// </summary>
     /// <param name="message">The message to send to a specific player/spectator.</param>
-    /// <param name="session">The target recipient.</param>
+    /// <param name="actor">The target recipient.</param>
-    private void SendMessage(BoundUserInterfaceMessage message, ICommonSession session)
+    private void SendMessage(BoundUserInterfaceMessage message, EntityUid actor)
     {
-        if (_uiSystem.TryGetUi(_owner, BlockGameUiKey.Key, out var bui))
+        _uiSystem.ServerSendUiMessage(_entityManager.GetEntity(message.Entity), BlockGameUiKey.Key, message, actor);
-            _uiSystem.TrySendUiMessage(bui, message, session);
     }
 
     /// <summary>
     /// Handles sending the current state of the game to a player that has just opened the UI.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    /// <param name="actor">The target recipient.</param>
-    public void UpdateNewPlayerUI(ICommonSession session)
+    public void UpdateNewPlayerUI(EntityUid actor)
     {
         if (_gameOver)
         {
-            SendMessage(new BlockGameMessages.BlockGameGameOverScreenMessage(Points, _highScorePlacement?.LocalPlacement, _highScorePlacement?.GlobalPlacement), session);
+            SendMessage(new BlockGameMessages.BlockGameGameOverScreenMessage(Points, _highScorePlacement?.LocalPlacement, _highScorePlacement?.GlobalPlacement), actor);
             return;
         }
 
         if (Paused)
-            SendMessage(new BlockGameMessages.BlockGameSetScreenMessage(BlockGameMessages.BlockGameScreen.Pause, Started), session);
+            SendMessage(new BlockGameMessages.BlockGameSetScreenMessage(BlockGameMessages.BlockGameScreen.Pause, Started), actor);
         else
-            SendMessage(new BlockGameMessages.BlockGameSetScreenMessage(BlockGameMessages.BlockGameScreen.Game, Started), session);
+            SendMessage(new BlockGameMessages.BlockGameSetScreenMessage(BlockGameMessages.BlockGameScreen.Game, Started), actor);
 
-        FullUpdate(session);
+        FullUpdate(actor);
     }
 
     /// <summary>
@@ -209,14 +207,14 @@ public sealed partial class BlockGame
     /// Handles broadcasting the full player-visible game state to a specific player/spectator.
     /// </summary>
     /// <param name="session">The target recipient.</param>
-    private void FullUpdate(ICommonSession session)
+    private void FullUpdate(EntityUid actor)
     {
-        UpdateFieldUI(session);
+        UpdateFieldUI(actor);
-        SendNextPieceUpdate(session);
+        SendNextPieceUpdate(actor);
-        SendHoldPieceUpdate(session);
+        SendHoldPieceUpdate(actor);
-        SendLevelUpdate(session);
+        SendLevelUpdate(actor);
-        SendPointsUpdate(session);
+        SendPointsUpdate(actor);
-        SendHighscoreUpdate(session);
+        SendHighscoreUpdate(actor);
     }
 
     /// <summary>
@@ -234,14 +232,13 @@ public sealed partial class BlockGame
     /// <summary>
     /// Handles broadcasting the current location of all of the blocks in the playfield + the active piece to a specific player/spectator.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    public void UpdateFieldUI(EntityUid actor)
-    public void UpdateFieldUI(ICommonSession session)
     {
         if (!Started)
             return;
 
         var computedField = ComputeField();
-        SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(computedField.ToArray(), BlockGameMessages.BlockGameVisualType.GameField), session);
+        SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(computedField.ToArray(), BlockGameMessages.BlockGameVisualType.GameField), actor);
     }
 
     /// <summary>
@@ -282,10 +279,9 @@ public sealed partial class BlockGame
     /// <summary>
     /// Broadcasts the state of the next queued piece to a specific viewer.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    private void SendNextPieceUpdate(EntityUid actor)
-    private void SendNextPieceUpdate(ICommonSession session)
     {
-        SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(NextPiece.BlocksForPreview(), BlockGameMessages.BlockGameVisualType.NextBlock), session);
+        SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(NextPiece.BlocksForPreview(), BlockGameMessages.BlockGameVisualType.NextBlock), actor);
     }
 
     /// <summary>
@@ -302,13 +298,12 @@ public sealed partial class BlockGame
     /// <summary>
     /// Broadcasts the state of the currently held piece to a specific viewer.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    private void SendHoldPieceUpdate(EntityUid actor)
-    private void SendHoldPieceUpdate(ICommonSession session)
     {
         if (HeldPiece.HasValue)
-            SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(HeldPiece.Value.BlocksForPreview(), BlockGameMessages.BlockGameVisualType.HoldBlock), session);
+            SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(HeldPiece.Value.BlocksForPreview(), BlockGameMessages.BlockGameVisualType.HoldBlock), actor);
         else
-            SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(Array.Empty<BlockGameBlock>(), BlockGameMessages.BlockGameVisualType.HoldBlock), session);
+            SendMessage(new BlockGameMessages.BlockGameVisualUpdateMessage(Array.Empty<BlockGameBlock>(), BlockGameMessages.BlockGameVisualType.HoldBlock), actor);
     }
 
     /// <summary>
@@ -322,10 +317,9 @@ public sealed partial class BlockGame
     /// <summary>
     /// Broadcasts the current game level to a specific viewer.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    private void SendLevelUpdate(EntityUid actor)
-    private void SendLevelUpdate(ICommonSession session)
     {
-        SendMessage(new BlockGameMessages.BlockGameLevelUpdateMessage(Level), session);
+        SendMessage(new BlockGameMessages.BlockGameLevelUpdateMessage(Level), actor);
     }
 
     /// <summary>
@@ -339,10 +333,9 @@ public sealed partial class BlockGame
     /// <summary>
     /// Broadcasts the current game score to a specific viewer.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    private void SendPointsUpdate(EntityUid actor)
-    private void SendPointsUpdate(ICommonSession session)
     {
-        SendMessage(new BlockGameMessages.BlockGameScoreUpdateMessage(Points), session);
+        SendMessage(new BlockGameMessages.BlockGameScoreUpdateMessage(Points), actor);
     }
 
     /// <summary>
@@ -356,9 +349,8 @@ public sealed partial class BlockGame
     /// <summary>
     /// Broadcasts the current game high score positions to a specific viewer.
     /// </summary>
-    /// <param name="session">The target recipient.</param>
+    private void SendHighscoreUpdate(EntityUid actor)
-    private void SendHighscoreUpdate(ICommonSession session)
     {
-        SendMessage(new BlockGameMessages.BlockGameHighScoreUpdateMessage(_arcadeSystem.GetLocalHighscores(), _arcadeSystem.GetGlobalHighscores()), session);
+        SendMessage(new BlockGameMessages.BlockGameHighScoreUpdateMessage(_arcadeSystem.GetLocalHighscores(), _arcadeSystem.GetGlobalHighscores()), actor);
     }
 }

Content.Server/Arcade/BlockGame/BlockGame.cs

@@ -9,8 +9,8 @@ public sealed partial class BlockGame
 {
     [Dependency] private readonly IEntityManager _entityManager = default!;
     [Dependency] private readonly IRobustRandom _random = default!;
-    private readonly ArcadeSystem _arcadeSystem = default!;
+    private readonly ArcadeSystem _arcadeSystem;
-    private readonly UserInterfaceSystem _uiSystem = default!;
+    private readonly UserInterfaceSystem _uiSystem;
 
     /// <summary>
     /// What entity is currently hosting this game of NT-BG.
@@ -78,7 +78,7 @@ public sealed partial class BlockGame
         _gameOver = true;
 
         if (_entityManager.TryGetComponent<BlockGameArcadeComponent>(_owner, out var cabinet)
-        && _entityManager.TryGetComponent<MetaDataComponent>(cabinet.Player?.AttachedEntity, out var meta))
+        && _entityManager.TryGetComponent<MetaDataComponent>(cabinet.Player, out var meta))
         {
             _highScorePlacement = _arcadeSystem.RegisterHighScore(meta.EntityName, Points);
             SendHighscoreUpdate();

Content.Server/Arcade/BlockGame/BlockGameArcadeComponent.cs

@@ -13,10 +13,10 @@ public sealed partial class BlockGameArcadeComponent : Component
     /// <summary>
     /// The player currently playing the active session of NT-BG.
     /// </summary>
-    public ICommonSession? Player = null;
+    public EntityUid? Player = null;
 
     /// <summary>
     /// The players currently viewing (but not playing) the active session of NT-BG.
     /// </summary>
-    public readonly List<ICommonSession> Spectators = new();
+    public readonly List<EntityUid> Spectators = new();
 }

Content.Server/Arcade/BlockGame/BlockGameArcadeSystem.cs

@@ -37,14 +37,12 @@ public sealed class BlockGameArcadeSystem : EntitySystem
         }
     }
 
-    private void UpdatePlayerStatus(EntityUid uid, ICommonSession session, PlayerBoundUserInterface? bui = null, BlockGameArcadeComponent? blockGame = null)
+    private void UpdatePlayerStatus(EntityUid uid, EntityUid actor, BlockGameArcadeComponent? blockGame = null)
     {
         if (!Resolve(uid, ref blockGame))
             return;
-        if (bui == null && !_uiSystem.TryGetUi(uid, BlockGameUiKey.Key, out bui))
-            return;
 
-        _uiSystem.TrySendUiMessage(bui, new BlockGameMessages.BlockGameUserStatusMessage(blockGame.Player == session), session);
+        _uiSystem.ServerSendUiMessage(uid, BlockGameUiKey.Key, new BlockGameMessages.BlockGameUserStatusMessage(blockGame.Player == actor), actor);
     }
 
     private void OnComponentInit(EntityUid uid, BlockGameArcadeComponent component, ComponentInit args)
@@ -54,33 +52,21 @@ public sealed class BlockGameArcadeSystem : EntitySystem
 
     private void OnAfterUIOpen(EntityUid uid, BlockGameArcadeComponent component, AfterActivatableUIOpenEvent args)
     {
-        if (!TryComp<ActorComponent>(args.User, out var actor))
-            return;
-        if (!_uiSystem.TryGetUi(uid, BlockGameUiKey.Key, out var bui))
-            return;
-
-        var session = actor.PlayerSession;
-        if (!bui.SubscribedSessions.Contains(session))
-            return;
-
         if (component.Player == null)
-            component.Player = session;
+            component.Player = args.Actor;
         else
-            component.Spectators.Add(session);
+            component.Spectators.Add(args.Actor);
 
-        UpdatePlayerStatus(uid, session, bui, component);
+        UpdatePlayerStatus(uid, args.Actor, component);
-        component.Game?.UpdateNewPlayerUI(session);
+        component.Game?.UpdateNewPlayerUI(args.Actor);
     }
 
     private void OnAfterUiClose(EntityUid uid, BlockGameArcadeComponent component, BoundUIClosedEvent args)
     {
-        if (args.Session is not { } session)
+        if (component.Player != args.Actor)
-            return;
-
-        if (component.Player != session)
         {
-            component.Spectators.Remove(session);
+            component.Spectators.Remove(args.Actor);
-            UpdatePlayerStatus(uid, session, blockGame: component);
+            UpdatePlayerStatus(uid, args.Actor, blockGame: component);
             return;
         }
 
@@ -88,11 +74,11 @@ public sealed class BlockGameArcadeSystem : EntitySystem
         if (component.Spectators.Count > 0)
         {
             component.Player = component.Spectators[0];
-            component.Spectators.Remove(component.Player);
+            component.Spectators.Remove(component.Player.Value);
-            UpdatePlayerStatus(uid, component.Player, blockGame: component);
+            UpdatePlayerStatus(uid, component.Player.Value, blockGame: component);
         }
 
-        UpdatePlayerStatus(uid, temp, blockGame: component);
+        UpdatePlayerStatus(uid, temp.Value, blockGame: component);
     }
 
     private void OnBlockPowerChanged(EntityUid uid, BlockGameArcadeComponent component, ref PowerChangedEvent args)
@@ -100,8 +86,7 @@ public sealed class BlockGameArcadeSystem : EntitySystem
         if (args.Powered)
             return;
 
-        if (_uiSystem.TryGetUi(uid, BlockGameUiKey.Key, out var bui))
+        _uiSystem.CloseUi(uid, BlockGameUiKey.Key);
-            _uiSystem.CloseAll(bui);
         component.Player = null;
         component.Spectators.Clear();
     }
@@ -112,7 +97,7 @@ public sealed class BlockGameArcadeSystem : EntitySystem
             return;
         if (!BlockGameUiKey.Key.Equals(msg.UiKey))
             return;
-        if (msg.Session != component.Player)
+        if (msg.Actor != component.Player)
             return;
 
         if (msg.PlayerAction == BlockGamePlayerAction.NewGame)

Content.Server/Arcade/SpaceVillainGame/SpaceVillainArcadeSystem.cs

@@ -90,12 +90,10 @@ public sealed partial class SpaceVillainArcadeSystem : EntitySystem
                 _audioSystem.PlayPvs(component.NewGameSound, uid, AudioParams.Default.WithVolume(-4f));
 
                 component.Game = new SpaceVillainGame(uid, component, this);
-                if (_uiSystem.TryGetUi(uid, SpaceVillainArcadeUiKey.Key, out var bui))
+                _uiSystem.ServerSendUiMessage(uid, SpaceVillainArcadeUiKey.Key, component.Game.GenerateMetaDataMessage());
-                    _uiSystem.SendUiMessage(bui, component.Game.GenerateMetaDataMessage());
                 break;
             case PlayerAction.RequestData:
-                if (_uiSystem.TryGetUi(uid, SpaceVillainArcadeUiKey.Key, out bui))
+                _uiSystem.ServerSendUiMessage(uid, SpaceVillainArcadeUiKey.Key, component.Game.GenerateMetaDataMessage());
-                    _uiSystem.SendUiMessage(bui, component.Game.GenerateMetaDataMessage());
                 break;
         }
     }
@@ -110,7 +108,6 @@ public sealed partial class SpaceVillainArcadeSystem : EntitySystem
         if (TryComp<ApcPowerReceiverComponent>(uid, out var power) && power.Powered)
             return;
 
-        if (_uiSystem.TryGetUi(uid, SpaceVillainArcadeUiKey.Key, out var bui))
+        _uiSystem.CloseUi(uid, SpaceVillainArcadeUiKey.Key);
-            _uiSystem.CloseAll(bui);
     }
 }

Content.Server/Arcade/SpaceVillainGame/SpaceVillainGame.Ui.cs

@@ -9,8 +9,7 @@ public sealed partial class SpaceVillainGame
     /// </summary>
     private void UpdateUi(EntityUid uid, bool metadata = false)
     {
-        if (_uiSystem.TryGetUi(uid, SpaceVillainArcadeUiKey.Key, out var bui))
+        _uiSystem.ServerSendUiMessage(uid, SpaceVillainArcadeUiKey.Key, metadata ? GenerateMetaDataMessage() : GenerateUpdateMessage());
-            _uiSystem.SendUiMessage(bui, metadata ? GenerateMetaDataMessage() : GenerateUpdateMessage());
     }
 
     private void UpdateUi(EntityUid uid, string message1, string message2, bool metadata = false)

Content.Server/Atmos/EntitySystems/GasAnalyzerSystem.cs

@@ -118,8 +118,7 @@ namespace Content.Server.Atmos.EntitySystems
             if (!Resolve(uid, ref component))
                 return;
 
-            if (user != null && TryComp<ActorComponent>(user, out var actor))
+            _userInterface.CloseUi(uid, GasAnalyzerUiKey.Key, user);
-                _userInterface.TryClose(uid, GasAnalyzerUiKey.Key, actor.PlayerSession);
 
             component.Enabled = false;
             Dirty(uid, component);
@@ -132,8 +131,6 @@ namespace Content.Server.Atmos.EntitySystems
         /// </summary>
         private void OnDisabledMessage(EntityUid uid, GasAnalyzerComponent component, GasAnalyzerDisableMessage message)
         {
-            if (message.Session.AttachedEntity is not { Valid: true })
-                return;
             DisableAnalyzer(uid, component);
         }
 
@@ -142,10 +139,7 @@ namespace Content.Server.Atmos.EntitySystems
             if (!Resolve(uid, ref component, false))
                 return;
 
-            if (!TryComp<ActorComponent>(user, out var actor))
+            _userInterface.OpenUi(uid, GasAnalyzerUiKey.Key, user);
-                return;
-
-            _userInterface.TryOpen(uid, GasAnalyzerUiKey.Key, actor.PlayerSession);
         }
 
         /// <summary>
@@ -242,7 +236,7 @@ namespace Content.Server.Atmos.EntitySystems
             if (gasMixList.Count == 0)
                 return false;
 
-            _userInterface.TrySendUiMessage(uid, GasAnalyzerUiKey.Key,
+            _userInterface.ServerSendUiMessage(uid, GasAnalyzerUiKey.Key,
                 new GasAnalyzerUserMessage(gasMixList.ToArray(),
                     component.Target != null ? Name(component.Target.Value) : string.Empty,
                     GetNetEntity(component.Target) ?? NetEntity.Invalid,

Content.Server/Atmos/EntitySystems/GasTankSystem.cs

@@ -75,7 +75,7 @@ namespace Content.Server.Atmos.EntitySystems
         public void UpdateUserInterface(Entity<GasTankComponent> ent, bool initialUpdate = false)
         {
             var (owner, component) = ent;
-            _ui.TrySetUiState(owner, SharedGasTankUiKey.Key,
+            _ui.SetUiState(owner, SharedGasTankUiKey.Key,
                 new GasTankBoundUserInterfaceState
                 {
                     TankPressure = component.Air?.Pressure ?? 0,

Content.Server/Atmos/Monitor/Components/AirAlarmComponent.cs

@@ -24,8 +24,6 @@ public sealed partial class AirAlarmComponent : Component
     public readonly Dictionary<string, GasVentScrubberData> ScrubberData = new();
     public readonly Dictionary<string, AtmosSensorData> SensorData = new();
 
-    public HashSet<NetUserId> ActivePlayers = new();
-
     public bool CanSync = true;
 
     /// <summary>

Content.Server/Atmos/Monitor/Systems/AirAlarmSystem.cs

@@ -223,8 +223,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnClose(EntityUid uid, AirAlarmComponent component, BoundUIClosedEvent args)
     {
-        component.ActivePlayers.Remove(args.Session.UserId);
+        if (!_ui.IsUiOpen(uid, SharedAirAlarmInterfaceKey.Key))
-        if (component.ActivePlayers.Count == 0)
             RemoveActiveInterface(uid);
     }
 
@@ -247,9 +246,6 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnActivate(EntityUid uid, AirAlarmComponent component, ActivateInWorldEvent args)
     {
-        if (!TryComp<ActorComponent>(args.User, out var actor))
-            return;
-
         if (TryComp<WiresPanelComponent>(uid, out var panel) && panel.Open)
         {
             args.Handled = false;
@@ -259,10 +255,7 @@ public sealed class AirAlarmSystem : EntitySystem
         if (!this.IsPowered(uid, EntityManager))
             return;
 
-        var ui = _ui.GetUiOrNull(uid, SharedAirAlarmInterfaceKey.Key);
+        _ui.OpenUi(uid, SharedAirAlarmInterfaceKey.Key, args.User);
-        if (ui != null)
-            _ui.OpenUi(ui, actor.PlayerSession);
-        component.ActivePlayers.Add(actor.PlayerSession.UserId);
         AddActiveInterface(uid);
         SyncAllDevices(uid);
         UpdateUI(uid, component);
@@ -270,7 +263,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnResyncAll(EntityUid uid, AirAlarmComponent component, AirAlarmResyncAllDevicesMessage args)
     {
-        if (!AccessCheck(uid, args.Session.AttachedEntity, component))
+        if (!AccessCheck(uid, args.Actor, component))
         {
             return;
         }
@@ -285,7 +278,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnUpdateAlarmMode(EntityUid uid, AirAlarmComponent component, AirAlarmUpdateAlarmModeMessage args)
     {
-        if (AccessCheck(uid, args.Session.AttachedEntity, component))
+        if (AccessCheck(uid, args.Actor, component))
         {
             var addr = string.Empty;
             if (TryComp<DeviceNetworkComponent>(uid, out var netConn))
@@ -309,7 +302,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnUpdateThreshold(EntityUid uid, AirAlarmComponent component, AirAlarmUpdateAlarmThresholdMessage args)
     {
-        if (AccessCheck(uid, args.Session.AttachedEntity, component))
+        if (AccessCheck(uid, args.Actor, component))
             SetThreshold(uid, args.Address, args.Type, args.Threshold, args.Gas);
         else
             UpdateUI(uid, component);
@@ -317,7 +310,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnUpdateDeviceData(EntityUid uid, AirAlarmComponent component, AirAlarmUpdateDeviceDataMessage args)
     {
-        if (AccessCheck(uid, args.Session.AttachedEntity, component)
+        if (AccessCheck(uid, args.Actor, component)
             && _deviceList.ExistsInDeviceList(uid, args.Address))
         {
             SetDeviceData(uid, args.Address, args.Data);
@@ -330,7 +323,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnCopyDeviceData(EntityUid uid, AirAlarmComponent component, AirAlarmCopyDeviceDataMessage args)
     {
-        if (!AccessCheck(uid, args.Session.AttachedEntity, component))
+        if (!AccessCheck(uid, args.Actor, component))
         {
            UpdateUI(uid, component);
             return;
@@ -377,7 +370,7 @@ public sealed class AirAlarmSystem : EntitySystem
 
     private void OnAtmosAlarm(EntityUid uid, AirAlarmComponent component, AtmosAlarmEvent args)
     {
-        if (component.ActivePlayers.Count != 0)
+        if (_ui.IsUiOpen(uid, SharedAirAlarmInterfaceKey.Key))
         {
             SyncAllDevices(uid);
         }
@@ -571,7 +564,7 @@ public sealed class AirAlarmSystem : EntitySystem
     /// </summary>
     private void ForceCloseAllInterfaces(EntityUid uid)
     {
-        _ui.TryCloseAll(uid, SharedAirAlarmInterfaceKey.Key);
+        _ui.CloseUi(uid, SharedAirAlarmInterfaceKey.Key);
     }
 
     private void OnAtmosUpdate(EntityUid uid, AirAlarmComponent alarm, ref AtmosDeviceUpdateEvent args)
@@ -639,7 +632,7 @@ public sealed class AirAlarmSystem : EntitySystem
             highestAlarm = AtmosAlarmType.Normal;
         }
 
-        _ui.TrySetUiState(
+        _ui.SetUiState(
             uid,
             SharedAirAlarmInterfaceKey.Key,
             new AirAlarmUIState(devNet.Address, deviceCount, pressure, temperature, dataToSend, alarm.CurrentMode, alarm.CurrentTab, highestAlarm.Value, alarm.AutoMode));

Content.Server/Atmos/Piping/Binary/EntitySystems/GasPressurePumpSystem.cs

@@ -98,7 +98,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
             UpdateAppearance(uid, pump);
 
             DirtyUI(uid, pump);
-            _userInterfaceSystem.TryCloseAll(uid, GasPressurePumpUiKey.Key);
+            _userInterfaceSystem.CloseUi(uid, GasPressurePumpUiKey.Key);
         }
 
         private void OnPumpActivate(EntityUid uid, GasPressurePumpComponent pump, ActivateInWorldEvent args)
@@ -108,7 +108,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
 
             if (Transform(uid).Anchored)
             {
-                _userInterfaceSystem.TryOpen(uid, GasPressurePumpUiKey.Key, actor.PlayerSession);
+                _userInterfaceSystem.OpenUi(uid, GasPressurePumpUiKey.Key, actor.PlayerSession);
                 DirtyUI(uid, pump);
             }
             else
@@ -123,7 +123,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
         {
             pump.Enabled = args.Enabled;
             _adminLogger.Add(LogType.AtmosPowerChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
+                $"{ToPrettyString(args.Actor):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
             DirtyUI(uid, pump);
             UpdateAppearance(uid, pump);
         }
@@ -132,7 +132,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
         {
             pump.TargetPressure = Math.Clamp(args.Pressure, 0f, Atmospherics.MaxOutputPressure);
             _adminLogger.Add(LogType.AtmosPressureChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the pressure on {ToPrettyString(uid):device} to {args.Pressure}kPa");
+                $"{ToPrettyString(args.Actor):player} set the pressure on {ToPrettyString(uid):device} to {args.Pressure}kPa");
             DirtyUI(uid, pump);
 
         }
@@ -142,7 +142,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
             if (!Resolve(uid, ref pump))
                 return;
 
-            _userInterfaceSystem.TrySetUiState(uid, GasPressurePumpUiKey.Key,
+            _userInterfaceSystem.SetUiState(uid, GasPressurePumpUiKey.Key,
                 new GasPressurePumpBoundUserInterfaceState(EntityManager.GetComponent<MetaDataComponent>(uid).EntityName, pump.TargetPressure, pump.Enabled));
         }
 

Content.Server/Atmos/Piping/Binary/EntitySystems/GasVolumePumpSystem.cs

@@ -128,7 +128,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
             UpdateAppearance(uid, pump);
 
             DirtyUI(uid, pump);
-            _userInterfaceSystem.TryCloseAll(uid, GasVolumePumpUiKey.Key);
+            _userInterfaceSystem.CloseUi(uid, GasVolumePumpUiKey.Key);
         }
 
         private void OnPumpActivate(EntityUid uid, GasVolumePumpComponent pump, ActivateInWorldEvent args)
@@ -138,7 +138,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
 
             if (Transform(uid).Anchored)
             {
-                _userInterfaceSystem.TryOpen(uid, GasVolumePumpUiKey.Key, actor.PlayerSession);
+                _userInterfaceSystem.OpenUi(uid, GasVolumePumpUiKey.Key, actor.PlayerSession);
                 DirtyUI(uid, pump);
             }
             else
@@ -153,7 +153,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
         {
             pump.Enabled = args.Enabled;
             _adminLogger.Add(LogType.AtmosPowerChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
+                $"{ToPrettyString(args.Actor):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
             DirtyUI(uid, pump);
             UpdateAppearance(uid, pump);
         }
@@ -162,7 +162,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
         {
             pump.TransferRate = Math.Clamp(args.TransferRate, 0f, pump.MaxTransferRate);
             _adminLogger.Add(LogType.AtmosVolumeChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the transfer rate on {ToPrettyString(uid):device} to {args.TransferRate}");
+                $"{ToPrettyString(args.Actor):player} set the transfer rate on {ToPrettyString(uid):device} to {args.TransferRate}");
             DirtyUI(uid, pump);
         }
 
@@ -171,7 +171,7 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
             if (!Resolve(uid, ref pump))
                 return;
 
-            _userInterfaceSystem.TrySetUiState(uid, GasVolumePumpUiKey.Key,
+            _userInterfaceSystem.SetUiState(uid, GasVolumePumpUiKey.Key,
                 new GasVolumePumpBoundUserInterfaceState(Name(uid), pump.TransferRate, pump.Enabled));
         }
 

Content.Server/Atmos/Piping/Trinary/EntitySystems/GasFilterSystem.cs

@@ -94,7 +94,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
             _ambientSoundSystem.SetAmbience(uid, false);
 
             DirtyUI(uid, filter);
-            _userInterfaceSystem.TryCloseAll(uid, GasFilterUiKey.Key);
+            _userInterfaceSystem.CloseUi(uid, GasFilterUiKey.Key);
         }
 
         private void OnFilterActivate(EntityUid uid, GasFilterComponent filter, ActivateInWorldEvent args)
@@ -104,7 +104,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
 
             if (EntityManager.GetComponent<TransformComponent>(uid).Anchored)
             {
-                _userInterfaceSystem.TryOpen(uid, GasFilterUiKey.Key, actor.PlayerSession);
+                _userInterfaceSystem.OpenUi(uid, GasFilterUiKey.Key, actor.PlayerSession);
                 DirtyUI(uid, filter);
             }
             else
@@ -120,7 +120,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
             if (!Resolve(uid, ref filter))
                 return;
 
-            _userInterfaceSystem.TrySetUiState(uid, GasFilterUiKey.Key,
+            _userInterfaceSystem.SetUiState(uid, GasFilterUiKey.Key,
                 new GasFilterBoundUserInterfaceState(MetaData(uid).EntityName, filter.TransferRate, filter.Enabled, filter.FilteredGas));
         }
 
@@ -136,7 +136,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
         {
             filter.Enabled = args.Enabled;
             _adminLogger.Add(LogType.AtmosPowerChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
+                $"{ToPrettyString(args.Actor):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
             DirtyUI(uid, filter);
             UpdateAppearance(uid, filter);
         }
@@ -145,7 +145,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
         {
             filter.TransferRate = Math.Clamp(args.Rate, 0f, filter.MaxTransferRate);
             _adminLogger.Add(LogType.AtmosVolumeChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the transfer rate on {ToPrettyString(uid):device} to {args.Rate}");
+                $"{ToPrettyString(args.Actor):player} set the transfer rate on {ToPrettyString(uid):device} to {args.Rate}");
             DirtyUI(uid, filter);
 
         }
@@ -158,7 +158,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
                 {
                     filter.FilteredGas = parsedGas;
                     _adminLogger.Add(LogType.AtmosFilterChanged, LogImpact.Medium,
-                        $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the filter on {ToPrettyString(uid):device} to {parsedGas.ToString()}");
+                        $"{ToPrettyString(args.Actor):player} set the filter on {ToPrettyString(uid):device} to {parsedGas.ToString()}");
                     DirtyUI(uid, filter);
                 }
                 else
@@ -170,7 +170,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
             {
                 filter.FilteredGas = null;
                 _adminLogger.Add(LogType.AtmosFilterChanged, LogImpact.Medium,
-                    $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the filter on {ToPrettyString(uid):device} to none");
+                    $"{ToPrettyString(args.Actor):player} set the filter on {ToPrettyString(uid):device} to none");
                 DirtyUI(uid, filter);
             }
         }

Content.Server/Atmos/Piping/Trinary/EntitySystems/GasMixerSystem.cs

@@ -134,7 +134,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
 
             DirtyUI(uid, mixer);
             UpdateAppearance(uid, mixer);
-            _userInterfaceSystem.TryCloseAll(uid, GasFilterUiKey.Key);
+            _userInterfaceSystem.CloseUi(uid, GasFilterUiKey.Key);
         }
 
         private void OnMixerActivate(EntityUid uid, GasMixerComponent mixer, ActivateInWorldEvent args)
@@ -144,7 +144,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
 
             if (Transform(uid).Anchored)
             {
-                _userInterfaceSystem.TryOpen(uid, GasMixerUiKey.Key, actor.PlayerSession);
+                _userInterfaceSystem.OpenUi(uid, GasMixerUiKey.Key, actor.PlayerSession);
                 DirtyUI(uid, mixer);
             }
             else
@@ -160,7 +160,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
             if (!Resolve(uid, ref mixer))
                 return;
 
-            _userInterfaceSystem.TrySetUiState(uid, GasMixerUiKey.Key,
+            _userInterfaceSystem.SetUiState(uid, GasMixerUiKey.Key,
                 new GasMixerBoundUserInterfaceState(EntityManager.GetComponent<MetaDataComponent>(uid).EntityName, mixer.TargetPressure, mixer.Enabled, mixer.InletOneConcentration));
         }
 
@@ -176,7 +176,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
         {
             mixer.Enabled = args.Enabled;
             _adminLogger.Add(LogType.AtmosPowerChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
+                $"{ToPrettyString(args.Actor):player} set the power on {ToPrettyString(uid):device} to {args.Enabled}");
             DirtyUI(uid, mixer);
             UpdateAppearance(uid, mixer);
         }
@@ -185,7 +185,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
         {
             mixer.TargetPressure = Math.Clamp(args.Pressure, 0f, mixer.MaxTargetPressure);
             _adminLogger.Add(LogType.AtmosPressureChanged, LogImpact.Medium,
-                $"{ToPrettyString(args.Session.AttachedEntity!.Value):player} set the pressure on {ToPrettyString(uid):device} to {args.Pressure}kPa");
+                $"{ToPrettyString(args.Actor):player} set the pressure on {ToPrettyString(uid):device} to {args.Pressure}kPa");
             DirtyUI(uid, mixer);
         }
 
@@ -196,7 +196,7 @@ namespace Content.Server.Atmos.Piping.Trinary.EntitySystems
             mixer.InletOneConcentration = nodeOne;
             mixer.InletTwoConcentration = 1.0f - mixer.InletOneConcentration;
             _adminLogger.Add(LogType.AtmosRatioChanged, LogImpact.Medium,
-                $"{EntityManager.ToPrettyString(args.Session.AttachedEntity!.Value):player} set the ratio on {EntityManager.ToPrettyString(uid):device} to {mixer.InletOneConcentration}:{mixer.InletTwoConcentration}");
+                $"{EntityManager.ToPrettyString(args.Actor):player} set the ratio on {EntityManager.ToPrettyString(uid):device} to {mixer.InletOneConcentration}:{mixer.InletTwoConcentration}");
             DirtyUI(uid, mixer);
         }
 

Content.Server/Atmos/Piping/Unary/EntitySystems/GasCanisterSystem.cs

@@ -96,7 +96,7 @@ public sealed class GasCanisterSystem : EntitySystem
             tankPressure = tankComponent.Air.Pressure;
         }
 
-        _ui.TrySetUiState(uid, GasCanisterUiKey.Key,
+        _ui.SetUiState(uid, GasCanisterUiKey.Key,
             new GasCanisterBoundUserInterfaceState(Name(uid),
                 canister.Air.Pressure, portStatus, tankLabel, tankPressure, canister.ReleasePressure,
                 canister.ReleaseValve, canister.MinReleasePressure, canister.MaxReleasePressure));
@@ -104,19 +104,19 @@ public sealed class GasCanisterSystem : EntitySystem
 
     private void OnHoldingTankEjectMessage(EntityUid uid, GasCanisterComponent canister, GasCanisterHoldingTankEjectMessage args)
     {
-        if (canister.GasTankSlot.Item == null || args.Session.AttachedEntity == null)
+        if (canister.GasTankSlot.Item == null)
             return;
 
         var item = canister.GasTankSlot.Item;
-        _slots.TryEjectToHands(uid, canister.GasTankSlot, args.Session.AttachedEntity);
+        _slots.TryEjectToHands(uid, canister.GasTankSlot, args.Actor);
-        _adminLogger.Add(LogType.CanisterTankEjected, LogImpact.Medium, $"Player {ToPrettyString(args.Session.AttachedEntity.GetValueOrDefault()):player} ejected tank {ToPrettyString(item):tank} from {ToPrettyString(uid):canister}");
+        _adminLogger.Add(LogType.CanisterTankEjected, LogImpact.Medium, $"Player {ToPrettyString(args.Actor):player} ejected tank {ToPrettyString(item):tank} from {ToPrettyString(uid):canister}");
     }
 
     private void OnCanisterChangeReleasePressure(EntityUid uid, GasCanisterComponent canister, GasCanisterChangeReleasePressureMessage args)
     {
         var pressure = Math.Clamp(args.Pressure, canister.MinReleasePressure, canister.MaxReleasePressure);
 
-        _adminLogger.Add(LogType.CanisterPressure, LogImpact.Medium, $"{ToPrettyString(args.Session.AttachedEntity.GetValueOrDefault()):player} set the release pressure on {ToPrettyString(uid):canister} to {args.Pressure}");
+        _adminLogger.Add(LogType.CanisterPressure, LogImpact.Medium, $"{ToPrettyString(args.Actor):player} set the release pressure on {ToPrettyString(uid):canister} to {args.Pressure}");
 
         canister.ReleasePressure = pressure;
         DirtyUI(uid, canister);
@@ -129,14 +129,14 @@ public sealed class GasCanisterSystem : EntitySystem
         impact = canister.GasTankSlot.HasItem ? LogImpact.Medium : LogImpact.High;
 
         var containedGasDict = new Dictionary<Gas, float>();
-        var containedGasArray = Gas.GetValues(typeof(Gas));
+        var containedGasArray = Enum.GetValues(typeof(Gas));
 
         for (int i = 0; i < containedGasArray.Length; i++)
         {
             containedGasDict.Add((Gas)i, canister.Air[i]);
         }
 
-        _adminLogger.Add(LogType.CanisterValve, impact, $"{ToPrettyString(args.Session.AttachedEntity.GetValueOrDefault()):player} set the valve on {ToPrettyString(uid):canister} to {args.Valve:valveState} while it contained [{string.Join(", ", containedGasDict)}]");
+        _adminLogger.Add(LogType.CanisterValve, impact, $"{ToPrettyString(args.Actor):player} set the valve on {ToPrettyString(uid):canister} to {args.Valve:valveState} while it contained [{string.Join(", ", containedGasDict)}]");
 
         canister.ReleaseValve = args.Valve;
         DirtyUI(uid, canister);
@@ -212,7 +212,7 @@ public sealed class GasCanisterSystem : EntitySystem
         if (args.Handled)
             return;
 
-        _ui.TryOpen(uid, GasCanisterUiKey.Key, actor.PlayerSession);
+        _ui.OpenUi(uid, GasCanisterUiKey.Key, actor.PlayerSession);
         args.Handled = true;
     }
 
@@ -224,7 +224,7 @@ public sealed class GasCanisterSystem : EntitySystem
         if (CheckLocked(uid, component, args.User))
             return;
 
-        _ui.TryOpen(uid, GasCanisterUiKey.Key, actor.PlayerSession);
+        _ui.OpenUi(uid, GasCanisterUiKey.Key, actor.PlayerSession);
         args.Handled = true;
     }
 

Content.Server/Atmos/Piping/Unary/EntitySystems/GasThermoMachineSystem.cs

@@ -144,7 +144,7 @@ namespace Content.Server.Atmos.Piping.Unary.EntitySystems
         private void OnToggleMessage(EntityUid uid, GasThermoMachineComponent thermoMachine, GasThermomachineToggleMessage args)
         {
             var powerState = _power.TogglePower(uid);
-            _adminLogger.Add(LogType.AtmosPowerChanged, $"{ToPrettyString(args.Session.AttachedEntity)} turned {(powerState ? "On" : "Off")} {ToPrettyString(uid)}");
+            _adminLogger.Add(LogType.AtmosPowerChanged, $"{ToPrettyString(args.Actor)} turned {(powerState ? "On" : "Off")} {ToPrettyString(uid)}");
             DirtyUI(uid, thermoMachine);
         }
 
@@ -155,7 +155,7 @@ namespace Content.Server.Atmos.Piping.Unary.EntitySystems
             else
                 thermoMachine.TargetTemperature = MathF.Max(args.Temperature, thermoMachine.MinTemperature);
             thermoMachine.TargetTemperature = MathF.Max(thermoMachine.TargetTemperature, Atmospherics.TCMB);
-            _adminLogger.Add(LogType.AtmosTemperatureChanged, $"{ToPrettyString(args.Session.AttachedEntity)} set temperature on {ToPrettyString(uid)} to {thermoMachine.TargetTemperature}");
+            _adminLogger.Add(LogType.AtmosTemperatureChanged, $"{ToPrettyString(args.Actor)} set temperature on {ToPrettyString(uid)} to {thermoMachine.TargetTemperature}");
             DirtyUI(uid, thermoMachine);
         }
 
@@ -168,8 +168,8 @@ namespace Content.Server.Atmos.Piping.Unary.EntitySystems
             if (!Resolve(uid, ref powerReceiver))
                 return;
 
-            _userInterfaceSystem.TrySetUiState(uid, ThermomachineUiKey.Key,
+            _userInterfaceSystem.SetUiState(uid, ThermomachineUiKey.Key,
-                new GasThermomachineBoundUserInterfaceState(thermoMachine.MinTemperature, thermoMachine.MaxTemperature, thermoMachine.TargetTemperature, !powerReceiver.PowerDisabled, IsHeater(thermoMachine)), null, ui);
+                new GasThermomachineBoundUserInterfaceState(thermoMachine.MinTemperature, thermoMachine.MaxTemperature, thermoMachine.TargetTemperature, !powerReceiver.PowerDisabled, IsHeater(thermoMachine)));
         }
 
         private void OnExamined(EntityUid uid, GasThermoMachineComponent thermoMachine, ExaminedEvent args)

Content.Server/Atmos/Portable/SpaceHeaterSystem.cs

@@ -163,7 +163,7 @@ public sealed class SpaceHeaterSystem : EntitySystem
         {
             return;
         }
-        _userInterfaceSystem.TrySetUiState(uid, SpaceHeaterUiKey.Key,
+        _userInterfaceSystem.SetUiState(uid, SpaceHeaterUiKey.Key,
             new SpaceHeaterBoundUserInterfaceState(spaceHeater.MinTemperature, spaceHeater.MaxTemperature, thermoMachine.TargetTemperature, !powerReceiver.PowerDisabled, spaceHeater.Mode, spaceHeater.PowerLevel));
     }
 

Content.Server/Audio/Jukebox/JukeboxSystem.cs

@@ -5,6 +5,7 @@ using Robust.Server.GameObjects;
 using Robust.Shared.Audio;
 using Robust.Shared.Audio.Components;
 using Robust.Shared.Audio.Systems;
+using Robust.Shared.Player;
 using Robust.Shared.Prototypes;
 using JukeboxComponent = Content.Shared.Audio.Jukebox.JukeboxComponent;
 
@@ -66,8 +67,11 @@ public sealed class JukeboxSystem : SharedJukeboxSystem
 
     private void OnJukeboxSetTime(EntityUid uid, JukeboxComponent component, JukeboxSetTimeMessage args)
     {
-        var offset = (args.Session.Channel.Ping * 1.5f) / 1000f;
+        if (TryComp(args.Actor, out ActorComponent? actorComp))
-        Audio.SetPlaybackPosition(component.AudioStream, args.SongTime + offset);
+        {
+            var offset = actorComp.PlayerSession.Channel.Ping * 1.5f / 1000f;
+            Audio.SetPlaybackPosition(component.AudioStream, args.SongTime + offset);
+        }
     }
 
     private void OnPowerChanged(Entity<JukeboxComponent> entity, ref PowerChangedEvent args)

Content.Server/Bed/Cryostorage/CryostorageSystem.cs

@@ -79,9 +79,7 @@ public sealed class CryostorageSystem : SharedCryostorageSystem
     private void OnRemoveItemBuiMessage(Entity<CryostorageComponent> ent, ref CryostorageRemoveItemBuiMessage args)
     {
         var (_, comp) = ent;
-        if (args.Session.AttachedEntity is not { } attachedEntity)
+        var attachedEntity = args.Actor;
-            return;
-
         var cryoContained = GetEntity(args.StoredEntity);
 
         if (!comp.StoredPlayers.Contains(cryoContained) || !IsInPausedMap(cryoContained))
@@ -114,6 +112,7 @@ public sealed class CryostorageSystem : SharedCryostorageSystem
         AdminLog.Add(LogType.Action, LogImpact.High,
             $"{ToPrettyString(attachedEntity):player} removed item {ToPrettyString(entity)} from cryostorage-contained player " +
             $"{ToPrettyString(cryoContained):player}, stored in cryostorage {ToPrettyString(ent)}");
+
         _container.TryRemoveFromContainer(entity.Value);
         _transform.SetCoordinates(entity.Value, Transform(attachedEntity).Coordinates);
         _hands.PickupOrDrop(attachedEntity, entity.Value);
@@ -122,8 +121,8 @@ public sealed class CryostorageSystem : SharedCryostorageSystem
 
     private void UpdateCryostorageUIState(Entity<CryostorageComponent> ent)
     {
-        var state = new CryostorageBuiState(GetAllContainedData(ent).ToList());
+        var state = new CryostorageBuiState(GetAllContainedData(ent));
-        _ui.TrySetUiState(ent, CryostorageUIKey.Key, state);
+        _ui.SetUiState(ent.Owner, CryostorageUIKey.Key, state);
     }
 
     private void OnPlayerSpawned(Entity<CryostorageContainedComponent> ent, ref PlayerSpawnCompleteEvent args)
@@ -293,12 +292,17 @@ public sealed class CryostorageSystem : SharedCryostorageSystem
             _chatManager.ChatMessageToOne(ChatChannel.Server, msg, msg, uid, false, actor.PlayerSession.Channel);
     }
 
-    private IEnumerable<CryostorageContainedPlayerData> GetAllContainedData(Entity<CryostorageComponent> ent)
+    private List<CryostorageContainedPlayerData> GetAllContainedData(Entity<CryostorageComponent> ent)
     {
+        var data = new List<CryostorageContainedPlayerData>();
+        data.EnsureCapacity(ent.Comp.StoredPlayers.Count);
+
         foreach (var contained in ent.Comp.StoredPlayers)
         {
-            yield return GetContainedData(contained);
+            data.Add(GetContainedData(contained));
         }
+
+        return data;
     }
 
     private CryostorageContainedPlayerData GetContainedData(EntityUid uid)

Content.Server/Cargo/Systems/CargoSystem.Bounty.cs

@@ -52,7 +52,7 @@ public sealed partial class CargoSystem
             return;
 
         var untilNextSkip = bountyDb.NextSkipTime - _timing.CurTime;
-        _uiSystem.TrySetUiState(uid, CargoConsoleUiKey.Bounty, new CargoBountyConsoleState(bountyDb.Bounties, untilNextSkip));
+        _uiSystem.SetUiState(uid, CargoConsoleUiKey.Bounty, new CargoBountyConsoleState(bountyDb.Bounties, untilNextSkip));
     }
 
     private void OnPrintLabelMessage(EntityUid uid, CargoBountyConsoleComponent component, BountyPrintLabelMessage args)
@@ -83,7 +83,7 @@ public sealed partial class CargoSystem
         if (!TryGetBountyFromId(station, args.BountyId, out var bounty))
             return;
 
-        if (args.Session.AttachedEntity is not { Valid: true } mob)
+        if (args.Actor is not { Valid: true } mob)
             return;
 
         if (TryComp<AccessReaderComponent>(uid, out var accessReaderComponent) &&
@@ -99,7 +99,7 @@ public sealed partial class CargoSystem
         FillBountyDatabase(station);
         db.NextSkipTime = _timing.CurTime + db.SkipDelay;
         var untilNextSkip = db.NextSkipTime - _timing.CurTime;
-        _uiSystem.TrySetUiState(uid, CargoConsoleUiKey.Bounty, new CargoBountyConsoleState(db.Bounties, untilNextSkip));
+        _uiSystem.SetUiState(uid, CargoConsoleUiKey.Bounty, new CargoBountyConsoleState(db.Bounties, untilNextSkip));
         _audio.PlayPvs(component.SkipSound, uid);
     }
 
@@ -462,10 +462,12 @@ public sealed partial class CargoSystem
         {
             if (_station.GetOwningStation(uid) is not { } station ||
                 !TryComp<StationCargoBountyDatabaseComponent>(station, out var db))
+            {
                 continue;
+            }
 
             var untilNextSkip = db.NextSkipTime - _timing.CurTime;
-            _uiSystem.TrySetUiState(uid, CargoConsoleUiKey.Bounty, new CargoBountyConsoleState(db.Bounties, untilNextSkip), ui: ui);
+            _uiSystem.SetUiState((uid, ui), CargoConsoleUiKey.Bounty, new CargoBountyConsoleState(db.Bounties, untilNextSkip));
         }
     }
 

Content.Server/Cargo/Systems/CargoSystem.Orders.cs

@@ -102,12 +102,12 @@ namespace Content.Server.Cargo.Systems
 
         private void OnApproveOrderMessage(EntityUid uid, CargoOrderConsoleComponent component, CargoConsoleApproveOrderMessage args)
         {
-            if (args.Session.AttachedEntity is not { Valid: true } player)
+            if (args.Actor is not { Valid: true } player)
                 return;
 
             if (!_accessReaderSystem.IsAllowed(player, uid))
             {
-                ConsolePopup(args.Session, Loc.GetString("cargo-console-order-not-allowed"));
+                ConsolePopup(args.Actor, Loc.GetString("cargo-console-order-not-allowed"));
                 PlayDenySound(uid, component);
                 return;
             }
@@ -119,7 +119,7 @@ namespace Content.Server.Cargo.Systems
                 !TryComp(station, out StationDataComponent? stationData) ||
                 !TryGetOrderDatabase(station, out var orderDatabase))
             {
-                ConsolePopup(args.Session, Loc.GetString("cargo-console-station-not-found"));
+                ConsolePopup(args.Actor, Loc.GetString("cargo-console-station-not-found"));
                 PlayDenySound(uid, component);
                 return;
             }
@@ -134,7 +134,7 @@ namespace Content.Server.Cargo.Systems
             // Invalid order
             if (!_protoMan.HasIndex<EntityPrototype>(order.ProductId))
             {
-                ConsolePopup(args.Session, Loc.GetString("cargo-console-invalid-product"));
+                ConsolePopup(args.Actor, Loc.GetString("cargo-console-invalid-product"));
                 PlayDenySound(uid, component);
                 return;
             }
@@ -145,7 +145,7 @@ namespace Content.Server.Cargo.Systems
             // Too many orders, avoid them getting spammed in the UI.
             if (amount >= capacity)
             {
-                ConsolePopup(args.Session, Loc.GetString("cargo-console-too-many"));
+                ConsolePopup(args.Actor, Loc.GetString("cargo-console-too-many"));
                 PlayDenySound(uid, component);
                 return;
             }
@@ -156,7 +156,7 @@ namespace Content.Server.Cargo.Systems
             if (cappedAmount != order.OrderQuantity)
             {
                 order.OrderQuantity = cappedAmount;
-                ConsolePopup(args.Session, Loc.GetString("cargo-console-snip-snip"));
+                ConsolePopup(args.Actor, Loc.GetString("cargo-console-snip-snip"));
                 PlayDenySound(uid, component);
             }
 
@@ -165,7 +165,7 @@ namespace Content.Server.Cargo.Systems
             // Not enough balance
             if (cost > bank.Balance)
             {
-                ConsolePopup(args.Session, Loc.GetString("cargo-console-insufficient-funds", ("cost", cost)));
+                ConsolePopup(args.Actor, Loc.GetString("cargo-console-insufficient-funds", ("cost", cost)));
                 PlayDenySound(uid, component);
                 return;
             }
@@ -180,7 +180,7 @@ namespace Content.Server.Cargo.Systems
 
                 if (ev.FulfillmentEntity == null)
                 {
-                    ConsolePopup(args.Session, Loc.GetString("cargo-console-unfulfilled"));
+                    ConsolePopup(args.Actor, Loc.GetString("cargo-console-unfulfilled"));
                     PlayDenySound(uid, component);
                     return;
                 }
@@ -200,7 +200,7 @@ namespace Content.Server.Cargo.Systems
                 ("approverJob", approverJob),
                 ("cost", cost));
             _radio.SendRadioMessage(uid, message, component.AnnouncementChannel, uid, escapeMarkup: false);
-            ConsolePopup(args.Session, Loc.GetString("cargo-console-trade-station", ("destination", MetaData(ev.FulfillmentEntity.Value).EntityName)));
+            ConsolePopup(args.Actor, Loc.GetString("cargo-console-trade-station", ("destination", MetaData(ev.FulfillmentEntity.Value).EntityName)));
 
             // Log order approval
             _adminLogger.Add(LogType.Action, LogImpact.Low,
@@ -271,7 +271,7 @@ namespace Content.Server.Cargo.Systems
 
         private void OnAddOrderMessage(EntityUid uid, CargoOrderConsoleComponent component, CargoConsoleAddOrderMessage args)
         {
-            if (args.Session.AttachedEntity is not { Valid: true } player)
+            if (args.Actor is not { Valid: true } player)
                 return;
 
             if (args.Amount <= 0)
@@ -319,9 +319,9 @@ namespace Content.Server.Cargo.Systems
                 !TryComp<StationCargoOrderDatabaseComponent>(station, out var orderDatabase) ||
                 !TryComp<StationBankAccountComponent>(station, out var bankAccount)) return;
 
-            if (_uiSystem.TryGetUi(consoleUid, CargoConsoleUiKey.Orders, out var bui))
+            if (_uiSystem.HasUi(consoleUid, CargoConsoleUiKey.Orders))
             {
-                _uiSystem.SetUiState(bui, new CargoConsoleInterfaceState(
+                _uiSystem.SetUiState(consoleUid, CargoConsoleUiKey.Orders, new CargoConsoleInterfaceState(
                     MetaData(station.Value).EntityName,
                     GetOutstandingOrderCount(orderDatabase),
                     orderDatabase.Capacity,
@@ -331,9 +331,9 @@ namespace Content.Server.Cargo.Systems
             }
         }
 
-        private void ConsolePopup(ICommonSession session, string text)
+        private void ConsolePopup(EntityUid actor, string text)
         {
-            _popup.PopupCursor(text, session);
+            _popup.PopupCursor(text, actor);
         }
 
         private void PlayDenySound(EntityUid uid, CargoOrderConsoleComponent component)

Content.Server/Cargo/Systems/CargoSystem.Shuttle.cs

@@ -54,21 +54,20 @@ public sealed partial class CargoSystem
 
     private void UpdatePalletConsoleInterface(EntityUid uid)
     {
-        var bui = _uiSystem.GetUi(uid, CargoPalletConsoleUiKey.Sale);
         if (Transform(uid).GridUid is not EntityUid gridUid)
         {
-            _uiSystem.SetUiState(bui,
+            _uiSystem.SetUiState(uid, CargoPalletConsoleUiKey.Sale,
             new CargoPalletConsoleInterfaceState(0, 0, false));
             return;
         }
         GetPalletGoods(gridUid, out var toSell, out var amount);
-        _uiSystem.SetUiState(bui,
+        _uiSystem.SetUiState(uid, CargoPalletConsoleUiKey.Sale,
             new CargoPalletConsoleInterfaceState((int) amount, toSell.Count, true));
     }
 
     private void OnPalletUIOpen(EntityUid uid, CargoPalletConsoleComponent component, BoundUIOpenedEvent args)
     {
-        var player = args.Session.AttachedEntity;
+        var player = args.Actor;
 
         if (player == null)
             return;
@@ -86,7 +85,7 @@ public sealed partial class CargoSystem
 
     private void OnPalletAppraise(EntityUid uid, CargoPalletConsoleComponent component, CargoPalletAppraiseMessage args)
     {
-        var player = args.Session.AttachedEntity;
+        var player = args.Actor;
 
         if (player == null)
             return;
@@ -108,8 +107,8 @@ public sealed partial class CargoSystem
         var orders = GetProjectedOrders(station ?? EntityUid.Invalid, orderDatabase, shuttle);
         var shuttleName = orderDatabase?.Shuttle != null ? MetaData(orderDatabase.Shuttle.Value).EntityName : string.Empty;
 
-        if (_uiSystem.TryGetUi(uid, CargoConsoleUiKey.Shuttle, out var bui))
+        if (_uiSystem.HasUi(uid, CargoConsoleUiKey.Shuttle))
-            _uiSystem.SetUiState(bui, new CargoShuttleConsoleBoundUserInterfaceState(
+            _uiSystem.SetUiState(uid, CargoConsoleUiKey.Shuttle, new CargoShuttleConsoleBoundUserInterfaceState(
                 station != null ? MetaData(station.Value).EntityName : Loc.GetString("cargo-shuttle-console-station-unknown"),
                 string.IsNullOrEmpty(shuttleName) ? Loc.GetString("cargo-shuttle-console-shuttle-not-found") : shuttleName,
                 orders
@@ -314,17 +313,16 @@ public sealed partial class CargoSystem
 
     private void OnPalletSale(EntityUid uid, CargoPalletConsoleComponent component, CargoPalletSellMessage args)
     {
-        var player = args.Session.AttachedEntity;
+        var player = args.Actor;
 
         if (player == null)
             return;
 
-        var bui = _uiSystem.GetUi(uid, CargoPalletConsoleUiKey.Sale);
         var xform = Transform(uid);
 
         if (xform.GridUid is not EntityUid gridUid)
         {
-            _uiSystem.SetUiState(bui,
+            _uiSystem.SetUiState(uid, CargoPalletConsoleUiKey.Sale,
             new CargoPalletConsoleInterfaceState(0, 0, false));
             return;
         }

Content.Server/CartridgeLoader/CartridgeLoaderSystem.cs

@@ -103,12 +103,12 @@ public sealed class CartridgeLoaderSystem : SharedCartridgeLoaderSystem
         if (!Resolve(loaderUid, ref loader))
             return;
 
-        if (!_userInterfaceSystem.TryGetUi(loaderUid, loader.UiKey, out var ui))
+        if (!_userInterfaceSystem.HasUi(loaderUid, loader.UiKey))
             return;
 
         var programs = GetAvailablePrograms(loaderUid, loader);
         var state = new CartridgeLoaderUiState(programs, GetNetEntity(loader.ActiveProgram));
-        _userInterfaceSystem.SetUiState(ui, state, session);
+        _userInterfaceSystem.SetUiState(loaderUid, loader.UiKey, state);
     }
 
     /// <summary>
@@ -127,8 +127,8 @@ public sealed class CartridgeLoaderSystem : SharedCartridgeLoaderSystem
         if (!Resolve(loaderUid, ref loader))
             return;
 
-        if (_userInterfaceSystem.TryGetUi(loaderUid, loader.UiKey, out var ui))
+        if (_userInterfaceSystem.HasUi(loaderUid, loader.UiKey))
-            _userInterfaceSystem.SetUiState(ui, state, session);
+            _userInterfaceSystem.SetUiState(loaderUid, loader.UiKey, state);
     }
 
     /// <summary>

Content.Server/Chemistry/EntitySystems/ChemMasterSystem.cs

@@ -80,7 +80,7 @@ namespace Content.Server.Chemistry.EntitySystems
                 chemMaster.Mode, BuildInputContainerInfo(inputContainer), BuildOutputContainerInfo(outputContainer),
                 bufferReagents, bufferCurrentVolume, chemMaster.PillType, chemMaster.PillDosageLimit, updateLabel);
 
-            _userInterfaceSystem.TrySetUiState(owner, ChemMasterUiKey.Key, state);
+            _userInterfaceSystem.SetUiState(owner, ChemMasterUiKey.Key, state);
         }
 
         private void OnSetModeMessage(Entity<ChemMasterComponent> chemMaster, ref ChemMasterSetModeMessage message)
@@ -179,7 +179,7 @@ namespace Content.Server.Chemistry.EntitySystems
 
         private void OnCreatePillsMessage(Entity<ChemMasterComponent> chemMaster, ref ChemMasterCreatePillsMessage message)
         {
-            var user = message.Session.AttachedEntity;
+            var user = message.Actor;
             var maybeContainer = _itemSlotsSystem.GetItemOrNull(chemMaster, SharedChemMaster.OutputSlotName);
             if (maybeContainer is not { Valid: true } container
                 || !TryComp(container, out StorageComponent? storage))
@@ -218,18 +218,9 @@ namespace Content.Server.Chemistry.EntitySystems
                 pill.PillType = chemMaster.Comp.PillType;
                 Dirty(item, pill);
 
-                if (user.HasValue)
+                // Log pill creation by a user
-                {
+                _adminLogger.Add(LogType.Action, LogImpact.Low,
-                    // Log pill creation by a user
+                    $"{ToPrettyString(user):user} printed {ToPrettyString(item):pill} {SharedSolutionContainerSystem.ToPrettyString(itemSolution.Comp.Solution)}");
-                    _adminLogger.Add(LogType.Action, LogImpact.Low,
-                        $"{ToPrettyString(user.Value):user} printed {ToPrettyString(item):pill} {SolutionContainerSystem.ToPrettyString(itemSolution.Comp.Solution)}");
-                }
-                else
-                {
-                    // Log pill creation by magic? This should never happen... right?
-                    _adminLogger.Add(LogType.Action, LogImpact.Low,
-                        $"Unknown printed {ToPrettyString(item):pill} {SolutionContainerSystem.ToPrettyString(itemSolution.Comp.Solution)}");
-                }
             }
 
             UpdateUiState(chemMaster);
@@ -238,7 +229,7 @@ namespace Content.Server.Chemistry.EntitySystems
 
         private void OnOutputToBottleMessage(Entity<ChemMasterComponent> chemMaster, ref ChemMasterOutputToBottleMessage message)
         {
-            var user = message.Session.AttachedEntity;
+            var user = message.Actor;
             var maybeContainer = _itemSlotsSystem.GetItemOrNull(chemMaster, SharedChemMaster.OutputSlotName);
             if (maybeContainer is not { Valid: true } container
                 || !_solutionContainerSystem.TryGetSolution(container, SharedChemMaster.BottleSolutionName, out var soln, out var solution))
@@ -260,18 +251,9 @@ namespace Content.Server.Chemistry.EntitySystems
             _labelSystem.Label(container, message.Label);
             _solutionContainerSystem.TryAddSolution(soln.Value, withdrawal);
 
-            if (user.HasValue)
+            // Log bottle creation by a user
-            {
+            _adminLogger.Add(LogType.Action, LogImpact.Low,
-                // Log bottle creation by a user
+                $"{ToPrettyString(user):user} bottled {ToPrettyString(container):bottle} {SharedSolutionContainerSystem.ToPrettyString(solution)}");
-                _adminLogger.Add(LogType.Action, LogImpact.Low,
-                    $"{ToPrettyString(user.Value):user} bottled {ToPrettyString(container):bottle} {SolutionContainerSystem.ToPrettyString(solution)}");
-            }
-            else
-            {
-                // Log bottle creation by magic? This should never happen... right?
-                _adminLogger.Add(LogType.Action, LogImpact.Low,
-                    $"Unknown bottled {ToPrettyString(container):bottle} {SolutionContainerSystem.ToPrettyString(solution)}");
-            }
 
             UpdateUiState(chemMaster);
             ClickSound(chemMaster);

Content.Server/Chemistry/EntitySystems/ReagentDispenserSystem.cs

@@ -62,7 +62,7 @@ namespace Content.Server.Chemistry.EntitySystems
             var inventory = GetInventory(reagentDispenser);
 
             var state = new ReagentDispenserBoundUserInterfaceState(outputContainerInfo, GetNetEntity(outputContainer), inventory, reagentDispenser.Comp.DispenseAmount);
-            _userInterfaceSystem.TrySetUiState(reagentDispenser, ReagentDispenserUiKey.Key, state);
+            _userInterfaceSystem.SetUiState(reagentDispenser.Owner, ReagentDispenserUiKey.Key, state);
         }
 
         private ContainerInfo? BuildOutputContainerInfo(EntityUid? container)

Content.Server/Cloning/CloningConsoleSystem.cs

@@ -135,17 +135,17 @@ namespace Content.Server.Cloning
 
         public void UpdateUserInterface(EntityUid consoleUid, CloningConsoleComponent consoleComponent)
         {
-            if (!_uiSystem.TryGetUi(consoleUid, CloningConsoleUiKey.Key, out var ui))
+            if (!_uiSystem.HasUi(consoleUid, CloningConsoleUiKey.Key))
                 return;
 
             if (!_powerReceiverSystem.IsPowered(consoleUid))
             {
-                _uiSystem.CloseAll(ui);
+                _uiSystem.CloseUis(consoleUid);
                 return;
             }
 
             var newState = GetUserInterfaceState(consoleComponent);
-            _uiSystem.SetUiState(ui, newState);
+            _uiSystem.SetUiState(consoleUid, CloningConsoleUiKey.Key, newState);
         }
 
         public void TryClone(EntityUid uid, EntityUid cloningPodUid, EntityUid scannerUid, CloningPodComponent? cloningPod = null, MedicalScannerComponent? scannerComp = null, CloningConsoleComponent? consoleComponent = null)

Content.Server/Clothing/Systems/ChameleonClothingSystem.cs

@@ -64,7 +64,7 @@ public sealed class ChameleonClothingSystem : SharedChameleonClothingSystem
             return;
 
         var state = new ChameleonBoundUserInterfaceState(component.Slot, component.Default);
-        _uiSystem.TrySetUiState(uid, ChameleonUiKey.Key, state);
+        _uiSystem.SetUiState(uid, ChameleonUiKey.Key, state);
     }
 
     /// <summary>

Content.Server/Communications/CommunicationsConsoleSystem.cs

@@ -82,8 +82,8 @@ namespace Content.Server.Communications
 
                 comp.UIUpdateAccumulator -= UIUpdateInterval;
 
-                if (_uiSystem.TryGetUi(uid, CommunicationsConsoleUiKey.Key, out var ui) && ui.SubscribedSessions.Count > 0)
+                if (_uiSystem.IsUiOpen(uid, CommunicationsConsoleUiKey.Key))
-                    UpdateCommsConsoleInterface(uid, comp, ui);
+                    UpdateCommsConsoleInterface(uid, comp);
             }
 
             base.Update(frameTime);
@@ -136,11 +136,8 @@ namespace Content.Server.Communications
         /// <summary>
         /// Updates the UI for a particular comms console.
         /// </summary>
-        public void UpdateCommsConsoleInterface(EntityUid uid, CommunicationsConsoleComponent comp, PlayerBoundUserInterface? ui = null)
+        public void UpdateCommsConsoleInterface(EntityUid uid, CommunicationsConsoleComponent comp)
         {
-            if (ui == null && !_uiSystem.TryGetUi(uid, CommunicationsConsoleUiKey.Key, out ui))
-                return;
-
             var stationUid = _stationSystem.GetOwningStation(uid);
             List<string>? levels = null;
             string currentLevel = default!;
@@ -168,7 +165,7 @@ namespace Content.Server.Communications
                 }
             }
 
-            _uiSystem.SetUiState(ui, new CommunicationsConsoleInterfaceState(
+            _uiSystem.SetUiState(uid, CommunicationsConsoleUiKey.Key, new CommunicationsConsoleInterfaceState(
                 CanAnnounce(comp),
                 CanCallOrRecall(comp),
                 levels,
@@ -219,12 +216,12 @@ namespace Content.Server.Communications
 
         private void OnSelectAlertLevelMessage(EntityUid uid, CommunicationsConsoleComponent comp, CommunicationsConsoleSelectAlertLevelMessage message)
         {
-            if (message.Session.AttachedEntity is not { Valid: true } mob)
+            if (message.Actor is not { Valid: true } mob)
                 return;
 
             if (!CanUse(mob, uid))
             {
-                _popupSystem.PopupCursor(Loc.GetString("comms-console-permission-denied"), message.Session, PopupType.Medium);
+                _popupSystem.PopupCursor(Loc.GetString("comms-console-permission-denied"), message.Actor, PopupType.Medium);
                 return;
             }
 
@@ -241,7 +238,7 @@ namespace Content.Server.Communications
             var maxLength = _cfg.GetCVar(CCVars.ChatMaxAnnouncementLength);
             var msg = SharedChatSystem.SanitizeAnnouncement(message.Message, maxLength);
             var author = Loc.GetString("comms-console-announcement-unknown-sender");
-            if (message.Session.AttachedEntity is { Valid: true } mob)
+            if (message.Actor is { Valid: true } mob)
             {
                 if (!CanAnnounce(comp))
                 {
@@ -250,7 +247,7 @@ namespace Content.Server.Communications
 
                 if (!CanUse(mob, uid))
                 {
-                    _popupSystem.PopupEntity(Loc.GetString("comms-console-permission-denied"), uid, message.Session);
+                    _popupSystem.PopupEntity(Loc.GetString("comms-console-permission-denied"), uid, message.Actor);
                     return;
                 }
 
@@ -263,7 +260,7 @@ namespace Content.Server.Communications
             comp.AnnouncementCooldownRemaining = comp.Delay;
             UpdateCommsConsoleInterface(uid, comp);
 
-            var ev = new CommunicationConsoleAnnouncementEvent(uid, comp, msg, message.Session.AttachedEntity);
+            var ev = new CommunicationConsoleAnnouncementEvent(uid, comp, msg, message.Actor);
             RaiseLocalEvent(ref ev);
 
             // allow admemes with vv
@@ -275,15 +272,14 @@ namespace Content.Server.Communications
             {
                 _chatSystem.DispatchGlobalAnnouncement(msg, title, announcementSound: comp.Sound, colorOverride: comp.Color);
 
-                if (message.Session.AttachedEntity != null)
+                _adminLogger.Add(LogType.Chat, LogImpact.Low, $"{ToPrettyString(message.Actor):player} has sent the following global announcement: {msg}");
-                    _adminLogger.Add(LogType.Chat, LogImpact.Low, $"{ToPrettyString(message.Session.AttachedEntity.Value):player} has sent the following global announcement: {msg}");
-
                 return;
             }
+
             _chatSystem.DispatchStationAnnouncement(uid, msg, title, colorOverride: comp.Color);
 
-            if (message.Session.AttachedEntity != null)
+            _adminLogger.Add(LogType.Chat, LogImpact.Low, $"{ToPrettyString(message.Actor):player} has sent the following station announcement: {msg}");
-                _adminLogger.Add(LogType.Chat, LogImpact.Low, $"{ToPrettyString(message.Session.AttachedEntity.Value):player} has sent the following station announcement: {msg}");
+
         }
 
         private void OnBroadcastMessage(EntityUid uid, CommunicationsConsoleComponent component, CommunicationsConsoleBroadcastMessage message)
@@ -298,8 +294,7 @@ namespace Content.Server.Communications
 
             _deviceNetworkSystem.QueuePacket(uid, null, payload, net.TransmitFrequency);
 
-            if (message.Session.AttachedEntity != null)
+            _adminLogger.Add(LogType.DeviceNetwork, LogImpact.Low, $"{ToPrettyString(message.Actor):player} has sent the following broadcast: {message.Message:msg}");
-                _adminLogger.Add(LogType.DeviceNetwork, LogImpact.Low, $"{ToPrettyString(message.Session.AttachedEntity.Value):player} has sent the following broadcast: {message.Message:msg}");
         }
 
         private void OnCallShuttleMessage(EntityUid uid, CommunicationsConsoleComponent comp, CommunicationsConsoleCallEmergencyShuttleMessage message)
@@ -307,12 +302,11 @@ namespace Content.Server.Communications
             if (!CanCallOrRecall(comp))
                 return;
 
-            if (message.Session.AttachedEntity is not { Valid: true } mob)
+            var mob = message.Actor;
-                return;
 
             if (!CanUse(mob, uid))
             {
-                _popupSystem.PopupEntity(Loc.GetString("comms-console-permission-denied"), uid, message.Session);
+                _popupSystem.PopupEntity(Loc.GetString("comms-console-permission-denied"), uid, message.Actor);
                 return;
             }
 
@@ -320,7 +314,7 @@ namespace Content.Server.Communications
             RaiseLocalEvent(ref ev);
             if (ev.Cancelled)
             {
-                _popupSystem.PopupEntity(ev.Reason ?? Loc.GetString("comms-console-shuttle-unavailable"), uid, message.Session);
+                _popupSystem.PopupEntity(ev.Reason ?? Loc.GetString("comms-console-shuttle-unavailable"), uid, message.Actor);
                 return;
             }
 
@@ -333,17 +327,14 @@ namespace Content.Server.Communications
             if (!CanCallOrRecall(comp))
                 return;
 
-            if (message.Session.AttachedEntity is not { Valid: true } mob)
+            if (!CanUse(message.Actor, uid))
-                return;
-
-            if (!CanUse(mob, uid))
             {
-                _popupSystem.PopupEntity(Loc.GetString("comms-console-permission-denied"), uid, message.Session);
+                _popupSystem.PopupEntity(Loc.GetString("comms-console-permission-denied"), uid, message.Actor);
                 return;
             }
 
             _roundEndSystem.CancelRoundEndCountdown(uid);
-            _adminLogger.Add(LogType.Action, LogImpact.Extreme, $"{ToPrettyString(mob):player} has recalled the shuttle.");
+            _adminLogger.Add(LogType.Action, LogImpact.Extreme, $"{ToPrettyString(message.Actor):player} has recalled the shuttle.");
         }
     }
 

Content.Server/Configurable/ConfigurationSystem.cs

@@ -30,10 +30,7 @@ public sealed class ConfigurationSystem : EntitySystem
         if (!TryComp(args.Used, out ToolComponent? tool) || !tool.Qualities.Contains(component.QualityNeeded))
             return;
 
-        if (!TryComp(args.User, out ActorComponent? actor))
+        args.Handled = _uiSystem.TryOpenUi(uid, ConfigurationUiKey.Key, args.User);
-            return;
-
-        args.Handled = _uiSystem.TryOpen(uid, ConfigurationUiKey.Key, actor.PlayerSession);
     }
 
     private void OnStartup(EntityUid uid, ConfigurationComponent component, ComponentStartup args)
@@ -43,8 +40,8 @@ public sealed class ConfigurationSystem : EntitySystem
 
     private void UpdateUi(EntityUid uid, ConfigurationComponent component)
     {
-        if (_uiSystem.TryGetUi(uid, ConfigurationUiKey.Key, out var ui))
+        if (_uiSystem.HasUi(uid, ConfigurationUiKey.Key))
-            _uiSystem.SetUiState(ui, new ConfigurationBoundUserInterfaceState(component.Config));
+            _uiSystem.SetUiState(uid, ConfigurationUiKey.Key, new ConfigurationBoundUserInterfaceState(component.Config));
     }
 
     private void OnUpdate(EntityUid uid, ConfigurationComponent component, ConfigurationUpdatedMessage args)

Content.Server/Crayon/CrayonSystem.cs

@@ -90,19 +90,14 @@ public sealed class CrayonSystem : SharedCrayonSystem
         if (args.Handled)
             return;
 
-        if (!TryComp<ActorComponent>(args.User, out var actor) ||
+        if (!_uiSystem.HasUi(uid, SharedCrayonComponent.CrayonUiKey.Key))
-            !_uiSystem.TryGetUi(uid, SharedCrayonComponent.CrayonUiKey.Key, out var ui))
         {
             return;
         }
 
-        _uiSystem.ToggleUi(ui, actor.PlayerSession);
+        _uiSystem.TryToggleUi(uid, SharedCrayonComponent.CrayonUiKey.Key, args.User);
-        if (ui.SubscribedSessions.Contains(actor.PlayerSession))
-        {
-            // Tell the user interface the selected stuff
-            _uiSystem.SetUiState(ui, new CrayonBoundUserInterfaceState(component.SelectedState, component.SelectableColor, component.Color));
-        }
 
+        _uiSystem.SetUiState(uid, SharedCrayonComponent.CrayonUiKey.Key, new CrayonBoundUserInterfaceState(component.SelectedState, component.SelectableColor, component.Color));
         args.Handled = true;
     }
 
@@ -140,8 +135,8 @@ public sealed class CrayonSystem : SharedCrayonSystem
 
     private void OnCrayonDropped(EntityUid uid, CrayonComponent component, DroppedEvent args)
     {
-        if (TryComp<ActorComponent>(args.User, out var actor))
+        // TODO: Use the existing event.
-            _uiSystem.TryClose(uid, SharedCrayonComponent.CrayonUiKey.Key, actor.PlayerSession);
+        _uiSystem.CloseUi(uid, SharedCrayonComponent.CrayonUiKey.Key, args.User);
     }
 
     private void UseUpCrayon(EntityUid uid, EntityUid user)

Content.Server/CrewManifest/CrewManifestSystem.cs

@@ -100,12 +100,12 @@ public sealed class CrewManifestSystem : EntitySystem
             return;
 
         var owningStation = _stationSystem.GetOwningStation(uid);
-        if (owningStation == null || ev.Session is not { } session)
+        if (owningStation == null || !TryComp(ev.Actor, out ActorComponent? actorComp))
         {
             return;
         }
 
-        CloseEui(owningStation.Value, session, uid);
+        CloseEui(owningStation.Value, actorComp.PlayerSession, uid);
     }
 
     /// <summary>
@@ -136,12 +136,12 @@ public sealed class CrewManifestSystem : EntitySystem
         {
             Log.Error(
                 "{User} tried to open crew manifest from wrong UI: {Key}. Correct owned is {ExpectedKey}",
-                msg.Session, msg.UiKey, component.OwnerKey);
+                msg.Actor, msg.UiKey, component.OwnerKey);
             return;
         }
 
         var owningStation = _stationSystem.GetOwningStation(uid);
-        if (owningStation == null || msg.Session is not { } session)
+        if (owningStation == null || !TryComp(msg.Actor, out ActorComponent? actorComp))
         {
             return;
         }
@@ -151,7 +151,7 @@ public sealed class CrewManifestSystem : EntitySystem
             return;
         }
 
-        OpenEui(owningStation.Value, session, uid);
+        OpenEui(owningStation.Value, actorComp.PlayerSession, uid);
     }
 
     /// <summary>

Content.Server/CriminalRecords/Systems/CriminalRecordsConsoleSystem.cs

@@ -77,7 +77,7 @@ public sealed class CriminalRecordsConsoleSystem : SharedCriminalRecordsConsoleS
             msg.Status == SecurityStatus.Suspected != (msg.Reason != null))
             return;
 
-        if (!CheckSelected(ent, msg.Session, out var mob, out var key))
+        if (!CheckSelected(ent, msg.Actor, out var mob, out var key))
             return;
 
         if (!_stationRecords.TryGetRecord<CriminalRecord>(key.Value, out var record) || record.Status == msg.Status)
@@ -150,7 +150,7 @@ public sealed class CriminalRecordsConsoleSystem : SharedCriminalRecordsConsoleS
 
     private void OnAddHistory(Entity<CriminalRecordsConsoleComponent> ent, ref CriminalRecordAddHistory msg)
     {
-        if (!CheckSelected(ent, msg.Session, out _, out var key))
+        if (!CheckSelected(ent, msg.Actor, out _, out var key))
             return;
 
         var line = msg.Line.Trim();
@@ -167,7 +167,7 @@ public sealed class CriminalRecordsConsoleSystem : SharedCriminalRecordsConsoleS
 
     private void OnDeleteHistory(Entity<CriminalRecordsConsoleComponent> ent, ref CriminalRecordDeleteHistory msg)
     {
-        if (!CheckSelected(ent, msg.Session, out _, out var key))
+        if (!CheckSelected(ent, msg.Actor, out _, out var key))
             return;
 
         if (!_criminalRecords.TryDeleteHistory(key.Value, msg.Index))
@@ -185,7 +185,7 @@ public sealed class CriminalRecordsConsoleSystem : SharedCriminalRecordsConsoleS
 
         if (!TryComp<StationRecordsComponent>(owningStation, out var stationRecords))
         {
-            _ui.TrySetUiState(uid, CriminalRecordsConsoleKey.Key, new CriminalRecordsConsoleState());
+            _ui.SetUiState(uid, CriminalRecordsConsoleKey.Key, new CriminalRecordsConsoleState());
             return;
         }
 
@@ -201,24 +201,22 @@ public sealed class CriminalRecordsConsoleSystem : SharedCriminalRecordsConsoleS
             state.SelectedKey = id;
         }
 
-        _ui.TrySetUiState(uid, CriminalRecordsConsoleKey.Key, state);
+        _ui.SetUiState(uid, CriminalRecordsConsoleKey.Key, state);
     }
 
     /// <summary>
     /// Boilerplate that most actions use, if they require that a record be selected.
     /// Obviously shouldn't be used for selecting records.
     /// </summary>
-    private bool CheckSelected(Entity<CriminalRecordsConsoleComponent> ent, ICommonSession session,
+    private bool CheckSelected(Entity<CriminalRecordsConsoleComponent> ent, EntityUid user,
         [NotNullWhen(true)] out EntityUid? mob, [NotNullWhen(true)] out StationRecordKey? key)
     {
         key = null;
         mob = null;
-        if (session.AttachedEntity is not { } user)
-            return false;
 
         if (!_access.IsAllowed(user, ent))
         {
-            _popup.PopupEntity(Loc.GetString("criminal-records-permission-denied"), ent, session);
+            _popup.PopupEntity(Loc.GetString("criminal-records-permission-denied"), ent, user);
             return false;
         }
 

Content.Server/DeviceLinking/Systems/SignalTimerSystem.cs

@@ -48,9 +48,9 @@ public sealed class SignalTimerSystem : EntitySystem
     {
         var time = TryComp<ActiveSignalTimerComponent>(uid, out var active) ? active.TriggerTime : TimeSpan.Zero;
 
-        if (_ui.TryGetUi(uid, SignalTimerUiKey.Key, out var bui))
+        if (_ui.HasUi(uid, SignalTimerUiKey.Key))
         {
-            _ui.SetUiState(bui, new SignalTimerBoundUserInterfaceState(component.Label,
+            _ui.SetUiState(uid, SignalTimerUiKey.Key, new SignalTimerBoundUserInterfaceState(component.Label,
                 TimeSpan.FromSeconds(component.Delay).Minutes.ToString("D2"),
                 TimeSpan.FromSeconds(component.Delay).Seconds.ToString("D2"),
                 component.CanEditLabel,
@@ -70,9 +70,9 @@ public sealed class SignalTimerSystem : EntitySystem
         _audio.PlayPvs(signalTimer.DoneSound, uid);
         _signalSystem.InvokePort(uid, signalTimer.TriggerPort);
 
-        if (_ui.TryGetUi(uid, SignalTimerUiKey.Key, out var bui))
+        if (_ui.HasUi(uid, SignalTimerUiKey.Key))
         {
-            _ui.SetUiState(bui, new SignalTimerBoundUserInterfaceState(signalTimer.Label,
+            _ui.SetUiState(uid, SignalTimerUiKey.Key, new SignalTimerBoundUserInterfaceState(signalTimer.Label,
                 TimeSpan.FromSeconds(signalTimer.Delay).Minutes.ToString("D2"),
                 TimeSpan.FromSeconds(signalTimer.Delay).Seconds.ToString("D2"),
                 signalTimer.CanEditLabel,
@@ -117,10 +117,7 @@ public sealed class SignalTimerSystem : EntitySystem
     /// <param name="uid">The entity that is interacted with.</param>
     private bool IsMessageValid(EntityUid uid, BoundUserInterfaceMessage message)
     {
-        if (message.Session.AttachedEntity is not { Valid: true } mob)
+        if (!_accessReader.IsAllowed(message.Actor, uid))
-            return false;
-
-        if (!_accessReader.IsAllowed(mob, uid))
             return false;
 
         return true;

Content.Server/DeviceNetwork/Systems/NetworkConfiguratorSystem.cs

@@ -89,7 +89,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
                 continue;
 
             //The network configurator is a handheld device. There can only ever be an ui session open for the player holding the device.
-            _uiSystem.TryCloseAll(uid, NetworkConfiguratorUiKey.Configure);
+            _uiSystem.CloseUi(uid, NetworkConfiguratorUiKey.Configure);
         }
     }
 
@@ -215,7 +215,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
 
     private void OnComponentRemoved(EntityUid uid, DeviceListComponent component, ComponentRemove args)
     {
-        _uiSystem.TryCloseAll(uid, NetworkConfiguratorUiKey.Configure);
+        _uiSystem.CloseUi(uid, NetworkConfiguratorUiKey.Configure);
     }
 
     /// <summary>
@@ -433,7 +433,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
             return;
 
 
-        _uiSystem.TryOpen(configuratorUid, NetworkConfiguratorUiKey.Link, actor.PlayerSession);
+        _uiSystem.OpenUi(configuratorUid, NetworkConfiguratorUiKey.Link, actor.PlayerSession);
         configurator.DeviceLinkTarget = targetUid;
 
 
@@ -464,7 +464,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         var sinkAddress = Resolve(sinkUid, ref sinkNetworkComponent, false) ? sinkNetworkComponent.Address : "";
 
         var state = new DeviceLinkUserInterfaceState(sources, sinks, links, sourceAddress, sinkAddress, defaults);
-        _uiSystem.TrySetUiState(configuratorUid, NetworkConfiguratorUiKey.Link, state);
+        _uiSystem.SetUiState(configuratorUid, NetworkConfiguratorUiKey.Link, state);
     }
 
     /// <summary>
@@ -478,7 +478,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         if (Delay(configurator))
             return;
 
-        if (!targetUid.HasValue || !TryComp(userUid, out ActorComponent? actor) || !AccessCheck(targetUid.Value, userUid, configurator))
+        if (!targetUid.HasValue || !AccessCheck(targetUid.Value, userUid, configurator))
             return;
 
         if (!TryComp(targetUid, out DeviceListComponent? list))
@@ -488,14 +488,13 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         configurator.ActiveDeviceList = targetUid;
         Dirty(configuratorUid, configurator);
 
-        if (!_uiSystem.TryGetUi(configuratorUid, NetworkConfiguratorUiKey.Configure, out var bui))
+        if (_uiSystem.TryOpenUi(configuratorUid, NetworkConfiguratorUiKey.Configure, userUid))
-            return;
+        {
-
+            _uiSystem.SetUiState(configuratorUid, NetworkConfiguratorUiKey.Configure, new DeviceListUserInterfaceState(
-        if (_uiSystem.OpenUi(bui, actor.PlayerSession))
-            _uiSystem.SetUiState(bui, new DeviceListUserInterfaceState(
                 _deviceListSystem.GetDeviceList(configurator.ActiveDeviceList.Value)
                     .Select(v => (v.Key, MetaData(v.Value).EntityName)).ToHashSet()
             ));
+        }
     }
 
     /// <summary>
@@ -523,8 +522,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
             component.Devices.Remove(invalidDevice);
         }
 
-        if (_uiSystem.TryGetUi(uid, NetworkConfiguratorUiKey.List, out var bui))
+        _uiSystem.SetUiState(uid, NetworkConfiguratorUiKey.List, new NetworkConfiguratorUserInterfaceState(devices));
-            _uiSystem.SetUiState(bui, new NetworkConfiguratorUserInterfaceState(devices));
     }
 
     /// <summary>
@@ -565,10 +563,10 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
     /// </summary>
     private void OnRemoveDevice(EntityUid uid, NetworkConfiguratorComponent component, NetworkConfiguratorRemoveDeviceMessage args)
     {
-        if (component.Devices.TryGetValue(args.Address, out var removedDevice) && args.Session.AttachedEntity != null)
+        if (component.Devices.TryGetValue(args.Address, out var removedDevice))
         {
             _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-                $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} removed buffered device {ToPrettyString(removedDevice):subject} from {ToPrettyString(uid):tool}");
+                $"{ToPrettyString(args.Actor):actor} removed buffered device {ToPrettyString(removedDevice):subject} from {ToPrettyString(uid):tool}");
         }
 
         component.Devices.Remove(args.Address);
@@ -583,10 +581,8 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
     /// </summary>
     private void OnClearDevice(EntityUid uid, NetworkConfiguratorComponent component, NetworkConfiguratorClearDevicesMessage args)
     {
-        if (args.Session.AttachedEntity != null)
+        _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-            _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
+            $"{ToPrettyString(args.Actor):actor} cleared buffered devices from {ToPrettyString(uid):tool}");
-                $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} cleared buffered devices from {ToPrettyString(uid):tool}");
-
 
         ClearDevices(uid, component);
         UpdateListUiState(uid, component);
@@ -609,9 +605,8 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         if (!configurator.ActiveDeviceLink.HasValue || !configurator.DeviceLinkTarget.HasValue)
             return;
 
-        if (args.Session.AttachedEntity != null)
+        _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-            _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
+            $"{ToPrettyString(args.Actor):actor} cleared links between {ToPrettyString(configurator.ActiveDeviceLink.Value):subject} and {ToPrettyString(configurator.DeviceLinkTarget.Value):subject2} with {ToPrettyString(uid):tool}");
-                $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} cleared links between {ToPrettyString(configurator.ActiveDeviceLink.Value):subject} and {ToPrettyString(configurator.DeviceLinkTarget.Value):subject2} with {ToPrettyString(uid):tool}");
 
         if (HasComp<DeviceLinkSourceComponent>(configurator.ActiveDeviceLink) && HasComp<DeviceLinkSinkComponent>(configurator.DeviceLinkTarget))
         {
@@ -649,7 +644,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         if (TryComp(configurator.ActiveDeviceLink, out DeviceLinkSourceComponent? activeSource) && TryComp(configurator.DeviceLinkTarget, out DeviceLinkSinkComponent? targetSink))
         {
             _deviceLinkSystem.ToggleLink(
-                args.Session.AttachedEntity,
+                args.Actor,
                 configurator.ActiveDeviceLink.Value,
                 configurator.DeviceLinkTarget.Value,
                 args.Source, args.Sink,
@@ -660,7 +655,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         else if (TryComp(configurator.DeviceLinkTarget, out DeviceLinkSourceComponent? targetSource) && TryComp(configurator.ActiveDeviceLink, out DeviceLinkSinkComponent? activeSink))
         {
             _deviceLinkSystem.ToggleLink(
-                args.Session.AttachedEntity,
+                args.Actor,
                 configurator.DeviceLinkTarget.Value,
                 configurator.ActiveDeviceLink.Value,
                 args.Source, args.Sink,
@@ -687,7 +682,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         if (TryComp(configurator.ActiveDeviceLink, out DeviceLinkSourceComponent? activeSource) && TryComp(configurator.DeviceLinkTarget, out DeviceLinkSinkComponent? targetSink))
         {
             _deviceLinkSystem.SaveLinks(
-                args.Session.AttachedEntity,
+                args.Actor,
                 configurator.ActiveDeviceLink.Value,
                 configurator.DeviceLinkTarget.Value,
                 args.Links,
@@ -705,7 +700,7 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         else if (TryComp(configurator.DeviceLinkTarget, out DeviceLinkSourceComponent? targetSource) && TryComp(configurator.ActiveDeviceLink, out DeviceLinkSinkComponent? activeSink))
         {
             _deviceLinkSystem.SaveLinks(
-                args.Session.AttachedEntity,
+                args.Actor,
                 configurator.DeviceLinkTarget.Value,
                 configurator.ActiveDeviceLink.Value,
                 args.Links,
@@ -735,29 +730,25 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
         switch (args.ButtonKey)
         {
             case NetworkConfiguratorButtonKey.Set:
-                if (args.Session.AttachedEntity != null)
+                _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-                    _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
+                    $"{ToPrettyString(args.Actor):actor} set device links to {ToPrettyString(component.ActiveDeviceList.Value):subject} with {ToPrettyString(uid):tool}");
-                        $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} set device links to {ToPrettyString(component.ActiveDeviceList.Value):subject} with {ToPrettyString(uid):tool}");
 
                 result = _deviceListSystem.UpdateDeviceList(component.ActiveDeviceList.Value, new HashSet<EntityUid>(component.Devices.Values));
                 break;
             case NetworkConfiguratorButtonKey.Add:
-                if (args.Session.AttachedEntity != null)
+                _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-                    _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
+                    $"{ToPrettyString(args.Actor):actor} added device links to {ToPrettyString(component.ActiveDeviceList.Value):subject} with {ToPrettyString(uid):tool}");
-                        $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} added device links to {ToPrettyString(component.ActiveDeviceList.Value):subject} with {ToPrettyString(uid):tool}");
 
                 result = _deviceListSystem.UpdateDeviceList(component.ActiveDeviceList.Value, new HashSet<EntityUid>(component.Devices.Values), true);
                 break;
             case NetworkConfiguratorButtonKey.Clear:
-                if (args.Session.AttachedEntity != null)
+                _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-                    _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
+                    $"{ToPrettyString(args.Actor):actor} cleared device links from {ToPrettyString(component.ActiveDeviceList.Value):subject} with {ToPrettyString(uid):tool}");
-                        $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} cleared device links from {ToPrettyString(component.ActiveDeviceList.Value):subject} with {ToPrettyString(uid):tool}");
                 result = _deviceListSystem.UpdateDeviceList(component.ActiveDeviceList.Value, new HashSet<EntityUid>());
                 break;
             case NetworkConfiguratorButtonKey.Copy:
-                if (args.Session.AttachedEntity != null)
+                _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
-                    _adminLogger.Add(LogType.DeviceLinking, LogImpact.Low,
+                    $"{ToPrettyString(args.Actor):actor} copied devices from {ToPrettyString(component.ActiveDeviceList.Value):subject} to {ToPrettyString(uid):tool}");
-                        $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} copied devices from {ToPrettyString(component.ActiveDeviceList.Value):subject} to {ToPrettyString(uid):tool}");
 
                 ClearDevices(uid, component);
 
@@ -783,8 +774,8 @@ public sealed class NetworkConfiguratorSystem : SharedNetworkConfiguratorSystem
             _ => "error"
         };
 
-        _popupSystem.PopupCursor(Loc.GetString(resultText), args.Session, PopupType.Medium);
+        _popupSystem.PopupCursor(Loc.GetString(resultText), args.Actor, PopupType.Medium);
-        _uiSystem.TrySetUiState(
+        _uiSystem.SetUiState(
             uid,
             NetworkConfiguratorUiKey.Configure,
             new DeviceListUserInterfaceState(

Content.Server/Disposal/Mailing/MailingUnitSystem.cs

@@ -159,8 +159,7 @@ public sealed class MailingUnitSystem : EntitySystem
 
         args.Handled = true;
         UpdateTargetList(uid, component);
-        if (_userInterfaceSystem.TryGetUi(uid, MailingUnitUiKey.Key, out var bui))
+        _userInterfaceSystem.OpenUi(uid, MailingUnitUiKey.Key, actor.PlayerSession);
-            _userInterfaceSystem.OpenUi(bui, actor.PlayerSession);
     }
 
     /// <summary>
@@ -178,8 +177,7 @@ public sealed class MailingUnitSystem : EntitySystem
             return;
 
         var state = new MailingUnitBoundUserInterfaceState(component.DisposalUnitInterfaceState, component.Target, component.TargetList, component.Tag);
-        if (_userInterfaceSystem.TryGetUi(uid, MailingUnitUiKey.Key, out var bui))
+        _userInterfaceSystem.SetUiState(uid, MailingUnitUiKey.Key, state);
-            _userInterfaceSystem.SetUiState(bui, state);
     }
 
     private void OnTargetSelected(EntityUid uid, MailingUnitComponent component, TargetSelectedMessage args)

Content.Server/Disposal/Tube/DisposalTubeSystem.cs

@@ -101,8 +101,9 @@ namespace Content.Server.Disposal.Tube
         /// <param name="msg">A user interface message from the client.</param>
         private void OnUiAction(EntityUid uid, DisposalRouterComponent router, SharedDisposalRouterComponent.UiActionMessage msg)
         {
-            if (!EntityManager.EntityExists(msg.Session.AttachedEntity))
+            if (!EntityManager.EntityExists(msg.Actor))
                 return;
+
             if (TryComp<PhysicsComponent>(uid, out var physBody) && physBody.BodyType != BodyType.Static)
                 return;
 
@@ -279,9 +280,9 @@ namespace Content.Server.Disposal.Tube
 
         private void OnOpenTaggerUI(EntityUid uid, DisposalTaggerComponent tagger, BoundUIOpenedEvent args)
         {
-            if (_uiSystem.TryGetUi(uid, DisposalTaggerUiKey.Key, out var bui))
+            if (_uiSystem.HasUi(uid, DisposalTaggerUiKey.Key))
             {
-                _uiSystem.SetUiState(bui,
+                _uiSystem.SetUiState(uid, DisposalTaggerUiKey.Key,
                     new DisposalTaggerUserInterfaceState(tagger.Tag));
             }
         }
@@ -292,13 +293,9 @@ namespace Content.Server.Disposal.Tube
         /// <returns>Returns a <see cref="SharedDisposalRouterComponent.DisposalRouterUserInterfaceState"/></returns>
         private void UpdateRouterUserInterface(EntityUid uid, DisposalRouterComponent router)
         {
-            var bui = _uiSystem.GetUiOrNull(uid, DisposalRouterUiKey.Key);
-            if (bui == null)
-                return;
-
             if (router.Tags.Count <= 0)
             {
-                _uiSystem.SetUiState(bui, new DisposalRouterUserInterfaceState(""));
+                _uiSystem.SetUiState(uid, DisposalRouterUiKey.Key, new DisposalRouterUserInterfaceState(""));
                 return;
             }
 
@@ -312,7 +309,7 @@ namespace Content.Server.Disposal.Tube
 
             taglist.Remove(taglist.Length - 2, 2);
 
-            _uiSystem.SetUiState(bui, new DisposalRouterUserInterfaceState(taglist.ToString()));
+            _uiSystem.SetUiState(uid, DisposalRouterUiKey.Key, new DisposalRouterUserInterfaceState(taglist.ToString()));
         }
 
         private void OnAnchorChange(EntityUid uid, DisposalTubeComponent component, ref AnchorStateChangedEvent args)

Content.Server/Disposal/Unit/EntitySystems/DisposalUnitSystem.cs

@@ -219,7 +219,7 @@ public sealed class DisposalUnitSystem : SharedDisposalUnitSystem
     #region UI Handlers
     private void OnUiButtonPressed(EntityUid uid, SharedDisposalUnitComponent component, SharedDisposalUnitComponent.UiButtonPressedMessage args)
     {
-        if (args.Session.AttachedEntity is not { Valid: true } player)
+        if (args.Actor is not { Valid: true } player)
         {
             return;
         }
@@ -235,7 +235,7 @@ public sealed class DisposalUnitSystem : SharedDisposalUnitSystem
                 _adminLogger.Add(LogType.Action, LogImpact.Low, $"{ToPrettyString(player):player} hit flush button on {ToPrettyString(uid)}, it's now {(component.Engaged ? "on" : "off")}");
                 break;
             case SharedDisposalUnitComponent.UiButton.Power:
-                _power.TogglePower(uid, user: args.Session.AttachedEntity);
+                _power.TogglePower(uid, user: args.Actor);
                 break;
             default:
                 throw new ArgumentOutOfRangeException($"{ToPrettyString(player):player} attempted to hit a nonexistant button on {ToPrettyString(uid)}");
@@ -268,7 +268,7 @@ public sealed class DisposalUnitSystem : SharedDisposalUnitSystem
         }
 
         args.Handled = true;
-        _ui.TryOpen(uid, SharedDisposalUnitComponent.DisposalUnitUiKey.Key, actor.PlayerSession);
+        _ui.OpenUi(uid, SharedDisposalUnitComponent.DisposalUnitUiKey.Key, actor.PlayerSession);
     }
 
     private void OnAfterInteractUsing(EntityUid uid, SharedDisposalUnitComponent component, AfterInteractUsingEvent args)
@@ -597,7 +597,7 @@ public sealed class DisposalUnitSystem : SharedDisposalUnitSystem
         var compState = GetState(uid, component);
         var stateString = Loc.GetString($"disposal-unit-state-{compState}");
         var state = new SharedDisposalUnitComponent.DisposalUnitBoundUserInterfaceState(Name(uid), stateString, EstimatedFullPressure(uid, component), powered, component.Engaged);
-        _ui.TrySetUiState(uid, SharedDisposalUnitComponent.DisposalUnitUiKey.Key, state);
+        _ui.SetUiState(uid, SharedDisposalUnitComponent.DisposalUnitUiKey.Key, state);
 
         var stateUpdatedEvent = new DisposalUnitUIStateUpdatedEvent(state);
         RaiseLocalEvent(uid, stateUpdatedEvent);
@@ -802,10 +802,7 @@ public sealed class DisposalUnitSystem : SharedDisposalUnitSystem
 
         QueueAutomaticEngage(uid, component);
 
-        if (TryComp(inserted, out ActorComponent? actor))
+        _ui.CloseUi(uid, SharedDisposalUnitComponent.DisposalUnitUiKey.Key, inserted);
-        {
-            _ui.TryClose(uid, SharedDisposalUnitComponent.DisposalUnitUiKey.Key, actor.PlayerSession);
-        }
 
         // Maybe do pullable instead? Eh still fine.
         Joints.RecursiveClearJoints(inserted);

Content.Server/Doors/Electronics/Systems/DoorElectronicsSystem.cs

@@ -39,7 +39,7 @@ public sealed class DoorElectronicsSystem : EntitySystem
         }
 
         var state = new DoorElectronicsConfigurationState(accesses);
-        _uiSystem.TrySetUiState(uid, DoorElectronicsConfigurationUiKey.Key, state);
+        _uiSystem.SetUiState(uid, DoorElectronicsConfigurationUiKey.Key, state);
     }
 
     private void OnChangeConfiguration(

Content.Server/Extinguisher/FireExtinguisherComponent.cs

@@ -3,7 +3,7 @@ using Robust.Shared.GameStates;
 
 namespace Content.Server.Extinguisher;
 
-[NetworkedComponent, RegisterComponent]
+[RegisterComponent]
 [Access(typeof(FireExtinguisherSystem))]
 public sealed partial class FireExtinguisherComponent : SharedFireExtinguisherComponent
 {

Content.Server/Eye/Blinding/ActivatableUIRequiresVisionSystem.cs

@@ -5,6 +5,7 @@ using Content.Shared.Eye.Blinding.Components;
 using Content.Shared.Eye.Blinding.Systems;
 using Robust.Shared.Player;
 using Robust.Server.GameObjects;
+using Robust.Shared.Collections;
 
 namespace Content.Server.Eye.Blinding;
 
@@ -37,24 +38,19 @@ public sealed class ActivatableUIRequiresVisionSystem : EntitySystem
         if (!args.Blind)
             return;
 
-        if (!TryComp<ActorComponent>(uid, out var actor))
+        var toClose = new ValueList<(EntityUid Entity, Enum Key)>();
-            return;
 
-        var uiList = _userInterfaceSystem.GetAllUIsForSession(actor.PlayerSession);
+        foreach (var bui in _userInterfaceSystem.GetActorUis(uid))
-        if (uiList == null)
-            return;
-
-        Queue<PlayerBoundUserInterface> closeList = new(); // foreach collection modified moment
-
-        foreach (var ui in uiList)
         {
-            if (HasComp<ActivatableUIRequiresVisionComponent>(ui.Owner))
+            if (HasComp<ActivatableUIRequiresVisionComponent>(bui.Entity))
-                closeList.Enqueue(ui);
+            {
+                toClose.Add(bui);
+            }
         }
 
-        foreach (var ui in closeList)
+        foreach (var bui in toClose)
         {
-            _userInterfaceSystem.CloseUi(ui, actor.PlayerSession);
+            _userInterfaceSystem.CloseUi(bui.Entity, bui.Key, uid);
         }
     }
 }

Content.Server/Fax/FaxSystem.cs

@@ -318,7 +318,7 @@ public sealed class FaxSystem : EntitySystem
 
     private void OnSendButtonPressed(EntityUid uid, FaxMachineComponent component, FaxSendMessage args)
     {
-        Send(uid, component, args.Session.AttachedEntity);
+        Send(uid, component, args.Actor);
     }
 
     private void OnRefreshButtonPressed(EntityUid uid, FaxMachineComponent component, FaxRefreshMessage args)
@@ -358,7 +358,7 @@ public sealed class FaxSystem : EntitySystem
                       component.SendTimeoutRemaining <= 0 &&
                       component.InsertingTimeRemaining <= 0;
         var state = new FaxUiState(component.FaxName, component.KnownFaxes, canSend, canCopy, isPaperInserted, component.DestinationFaxAddress);
-        _userInterface.TrySetUiState(uid, FaxUiKey.Key, state);
+        _userInterface.SetUiState(uid, FaxUiKey.Key, state);
     }
 
     /// <summary>
@@ -417,12 +417,8 @@ public sealed class FaxSystem : EntitySystem
 
         UpdateUserInterface(uid, component);
 
-        if (args.Session.AttachedEntity != null)
+        _adminLogger.Add(LogType.Action, LogImpact.Low,
-            _adminLogger.Add(LogType.Action, LogImpact.Low,
+            $"{ToPrettyString(args.Actor):actor} added print job to {ToPrettyString(uid):tool} with text: {args.Content}");
-                $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} added print job to {ToPrettyString(uid):tool} with text: {args.Content}");
-        else
-            _adminLogger.Add(LogType.Action, LogImpact.Low,
-                $"Someone added print job to {ToPrettyString(uid):tool} with text: {args.Content}");
     }
 
     /// <summary>
@@ -457,9 +453,8 @@ public sealed class FaxSystem : EntitySystem
 
         UpdateUserInterface(uid, component);
 
-        if (args.Session.AttachedEntity != null)
+        _adminLogger.Add(LogType.Action, LogImpact.Low,
-            _adminLogger.Add(LogType.Action, LogImpact.Low,
+            $"{ToPrettyString(args.Actor):actor} added copy job to {ToPrettyString(uid):tool} with text: {ToPrettyString(component.PaperSlot.Item):subject}");
-                $"{ToPrettyString(args.Session.AttachedEntity.Value):actor} added copy job to {ToPrettyString(uid):tool} with text: {ToPrettyString(component.PaperSlot.Item):subject}");
     }
 
     /// <summary>

Content.Server/Forensics/Systems/ForensicScannerSystem.cs

@@ -52,8 +52,7 @@ namespace Content.Server.Forensics
                 component.PrintCooldown,
                 component.PrintReadyAt);
 
-            if (!_uiSystem.TrySetUiState(uid, ForensicScannerUiKey.Key, state))
+            _uiSystem.SetUiState(uid, ForensicScannerUiKey.Key, state);
-                Log.Warning($"{ToPrettyString(uid)} was unable to set UI state.");
         }
 
         private void OnDoAfter(EntityUid uid, ForensicScannerComponent component, DoAfterEvent args)
@@ -163,23 +162,14 @@ namespace Content.Server.Forensics
 
         private void OpenUserInterface(EntityUid user, Entity<ForensicScannerComponent> scanner)
         {
-            if (!TryComp<ActorComponent>(user, out var actor))
-                return;
-
             UpdateUserInterface(scanner, scanner.Comp);
 
-            _uiSystem.TryOpen(scanner, ForensicScannerUiKey.Key, actor.PlayerSession);
+            _uiSystem.OpenUi(scanner.Owner, ForensicScannerUiKey.Key, user);
         }
 
         private void OnPrint(EntityUid uid, ForensicScannerComponent component, ForensicScannerPrintMessage args)
         {
-            if (!args.Session.AttachedEntity.HasValue)
+            var user = args.Actor;
-            {
-                Log.Warning($"{ToPrettyString(uid)} got OnPrint without Session.AttachedEntity");
-                return;
-            }
-
-            var user = args.Session.AttachedEntity.Value;
 
             if (_gameTiming.CurTime < component.PrintReadyAt)
             {
@@ -191,7 +181,7 @@ namespace Content.Server.Forensics
 
             // Spawn a piece of paper.
             var printed = EntityManager.SpawnEntity(component.MachineOutput, Transform(uid).Coordinates);
-            _handsSystem.PickupOrDrop(args.Session.AttachedEntity, printed, checkActionBlocker: false);
+            _handsSystem.PickupOrDrop(args.Actor, printed, checkActionBlocker: false);
 
             if (!HasComp<PaperComponent>(printed))
             {
@@ -240,9 +230,6 @@ namespace Content.Server.Forensics
 
         private void OnClear(EntityUid uid, ForensicScannerComponent component, ForensicScannerClearMessage args)
         {
-            if (!args.Session.AttachedEntity.HasValue)
-                return;
-
             component.Fingerprints = new();
             component.Fibers = new();
             component.DNAs = new();

Content.Server/Gateway/Systems/GatewaySystem.cs

@@ -129,7 +129,7 @@ public sealed class GatewaySystem : EntitySystem
             unlockTime
         );
 
-        _ui.TrySetUiState(uid, GatewayUiKey.Key, state);
+        _ui.SetUiState(uid, GatewayUiKey.Key, state);
     }
 
     private void UpdateAppearance(EntityUid uid)
@@ -139,12 +139,14 @@ public sealed class GatewaySystem : EntitySystem
 
     private void OnOpenPortal(EntityUid uid, GatewayComponent comp, GatewayOpenPortalMessage args)
     {
-        if (args.Session.AttachedEntity == null || GetNetEntity(uid) == args.Destination ||
+        if (GetNetEntity(uid) == args.Destination ||
             !comp.Enabled || !comp.Interactable)
+        {
             return;
+        }
 
         // if the gateway has an access reader check it before allowing opening
-        var user = args.Session.AttachedEntity.Value;
+        var user = args.Actor;
         if (CheckAccess(user, uid, comp))
             return;
 

Content.Server/Gravity/GravityGeneratorSystem.cs

@@ -131,13 +131,13 @@ namespace Content.Server.Gravity
         }
 
         private void SetSwitchedOn(EntityUid uid, GravityGeneratorComponent component, bool on,
-            ApcPowerReceiverComponent? powerReceiver = null, ICommonSession? session = null)
+            ApcPowerReceiverComponent? powerReceiver = null, EntityUid? user = null)
         {
             if (!Resolve(uid, ref powerReceiver))
                 return;
 
-            if (session is { AttachedEntity: { } })
+            if (user != null)
-                _adminLogger.Add(LogType.Action, on ? LogImpact.Medium : LogImpact.High, $"{session:player} set ${ToPrettyString(uid):target} to {(on ? "on" : "off")}");
+                _adminLogger.Add(LogType.Action, on ? LogImpact.Medium : LogImpact.High, $"{ToPrettyString(user)} set ${ToPrettyString(uid):target} to {(on ? "on" : "off")}");
 
             component.SwitchedOn = on;
             UpdatePowerState(component, powerReceiver);
@@ -154,7 +154,7 @@ namespace Content.Server.Gravity
         private void UpdateUI(Entity<GravityGeneratorComponent, ApcPowerReceiverComponent> ent, float chargeRate)
         {
             var (_, component, powerReceiver) = ent;
-            if (!_uiSystem.IsUiOpen(ent, SharedGravityGeneratorComponent.GravityGeneratorUiKey.Key))
+            if (!_uiSystem.IsUiOpen(ent.Owner, SharedGravityGeneratorComponent.GravityGeneratorUiKey.Key))
                 return;
 
             var chargeTarget = chargeRate < 0 ? 0 : component.MaxCharge;
@@ -189,8 +189,8 @@ namespace Content.Server.Gravity
                 chargeEta
             );
 
-            _uiSystem.TrySetUiState(
+            _uiSystem.SetUiState(
-                ent,
+                ent.Owner,
                 SharedGravityGeneratorComponent.GravityGeneratorUiKey.Key,
                 state);
 
@@ -209,9 +209,6 @@ namespace Content.Server.Gravity
 
         private void OnInteractHand(EntityUid uid, GravityGeneratorComponent component, InteractHandEvent args)
         {
-            if (!EntityManager.TryGetComponent(args.User, out ActorComponent? actor))
-                return;
-
             ApcPowerReceiverComponent? powerReceiver = default!;
             if (!Resolve(uid, ref powerReceiver))
                 return;
@@ -220,7 +217,7 @@ namespace Content.Server.Gravity
             if (!component.Intact || powerReceiver.PowerReceived < component.IdlePowerUse)
                 return;
 
-            _uiSystem.TryOpen(uid, SharedGravityGeneratorComponent.GravityGeneratorUiKey.Key, actor.PlayerSession);
+            _uiSystem.OpenUi(uid, SharedGravityGeneratorComponent.GravityGeneratorUiKey.Key, args.User);
             component.NeedUIUpdate = true;
         }
 
@@ -287,7 +284,7 @@ namespace Content.Server.Gravity
             GravityGeneratorComponent component,
             SharedGravityGeneratorComponent.SwitchGeneratorMessage args)
         {
-            SetSwitchedOn(uid, component, args.On, session:args.Session);
+            SetSwitchedOn(uid, component, args.On, user: args.Actor);
         }
     }
 }

Content.Server/Humanoid/Systems/HumanoidAppearanceSystem.Modifier.cs

@@ -32,8 +32,8 @@ public sealed partial class HumanoidAppearanceSystem
             Icon = new SpriteSpecifier.Rsi(new("/Textures/Mobs/Customization/reptilian_parts.rsi"), "tail_smooth"),
             Act = () =>
             {
-                _uiSystem.TryOpen(uid, HumanoidMarkingModifierKey.Key, actor.PlayerSession);
+                _uiSystem.OpenUi(uid, HumanoidMarkingModifierKey.Key, actor.PlayerSession);
-                _uiSystem.TrySetUiState(
+                _uiSystem.SetUiState(
                     uid,
                     HumanoidMarkingModifierKey.Key,
                     new HumanoidMarkingModifierState(component.MarkingSet, component.Species,
@@ -48,8 +48,7 @@ public sealed partial class HumanoidAppearanceSystem
     private void OnBaseLayersSet(EntityUid uid, HumanoidAppearanceComponent component,
         HumanoidMarkingModifierBaseLayersSetMessage message)
     {
-        if (message.Session is not { } player
+        if (!_adminManager.HasAdminFlag(message.Actor, AdminFlags.Fun))
-            || !_adminManager.HasAdminFlag(player, AdminFlags.Fun))
         {
             return;
         }
@@ -67,7 +66,7 @@ public sealed partial class HumanoidAppearanceSystem
 
         if (message.ResendState)
         {
-            _uiSystem.TrySetUiState(
+            _uiSystem.SetUiState(
                 uid,
                 HumanoidMarkingModifierKey.Key,
                 new HumanoidMarkingModifierState(component.MarkingSet, component.Species,
@@ -81,8 +80,7 @@ public sealed partial class HumanoidAppearanceSystem
     private void OnMarkingsSet(EntityUid uid, HumanoidAppearanceComponent component,
         HumanoidMarkingModifierMarkingSetMessage message)
     {
-        if (message.Session is not { } player
+        if (!_adminManager.HasAdminFlag(message.Actor, AdminFlags.Fun))
-            || !_adminManager.HasAdminFlag(player, AdminFlags.Fun))
         {
             return;
         }
@@ -92,7 +90,7 @@ public sealed partial class HumanoidAppearanceSystem
 
         if (message.ResendState)
         {
-            _uiSystem.TrySetUiState(
+            _uiSystem.SetUiState(
                 uid,
                 HumanoidMarkingModifierKey.Key,
                 new HumanoidMarkingModifierState(component.MarkingSet, component.Species,

Content.Server/Instruments/InstrumentComponent.cs

@@ -1,6 +1,7 @@
 using Content.Server.UserInterface;
 using Content.Shared.Instruments;
 using Robust.Shared.Player;
+using ActivatableUIComponent = Content.Shared.UserInterface.ActivatableUIComponent;
 
 namespace Content.Server.Instruments;
 
@@ -16,9 +17,9 @@ public sealed partial class InstrumentComponent : SharedInstrumentComponent
     [ViewVariables] public uint LastSequencerTick = 0;
 
     // TODO Instruments: Make this ECS
-    public ICommonSession? InstrumentPlayer =>
+    public EntityUid? InstrumentPlayer =>
         _entMan.GetComponentOrNull<ActivatableUIComponent>(Owner)?.CurrentSingleUser
-        ?? _entMan.GetComponentOrNull<ActorComponent>(Owner)?.PlayerSession;
+        ?? _entMan.GetComponentOrNull<ActorComponent>(Owner)?.PlayerSession.AttachedEntity;
 }
 
 [RegisterComponent]

Content.Server/Instruments/InstrumentSystem.cs

@@ -111,7 +111,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
         if (!TryComp(uid, out InstrumentComponent? instrument))
             return;
 
-        if (args.SenderSession != instrument.InstrumentPlayer)
+        if (args.SenderSession.AttachedEntity != instrument.InstrumentPlayer)
             return;
 
         instrument.Playing = true;
@@ -125,7 +125,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
         if (!TryComp(uid, out InstrumentComponent? instrument))
             return;
 
-        if (args.SenderSession != instrument.InstrumentPlayer)
+        if (args.SenderSession.AttachedEntity != instrument.InstrumentPlayer)
             return;
 
         Clean(uid, instrument);
@@ -142,7 +142,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
         if (!TryComp(uid, out InstrumentComponent? instrument))
             return;
 
-        if (args.SenderSession != instrument.InstrumentPlayer)
+        if (args.SenderSession.AttachedEntity != instrument.InstrumentPlayer)
             return;
 
         if (master != null)
@@ -174,7 +174,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
         if (!TryComp(uid, out InstrumentComponent? instrument))
             return;
 
-        if (args.SenderSession != instrument.InstrumentPlayer)
+        if (args.SenderSession.AttachedEntity != instrument.InstrumentPlayer)
             return;
 
         if (msg.Channel == RobustMidiEvent.PercussionChannel && !instrument.AllowPercussion)
@@ -194,8 +194,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
     private void OnBoundUIClosed(EntityUid uid, InstrumentComponent component, BoundUIClosedEvent args)
     {
         if (HasComp<ActiveInstrumentComponent>(uid)
-            && _bui.TryGetUi(uid, args.UiKey, out var bui)
+            && !_bui.IsUiOpen(uid, args.UiKey))
-            && bui.SubscribedSessions.Count == 0)
         {
             RemComp<ActiveInstrumentComponent>(uid);
         }
@@ -232,7 +231,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
         var instrumentQuery = EntityManager.GetEntityQuery<InstrumentComponent>();
 
         if (!TryComp(uid, out InstrumentComponent? originInstrument)
-            || originInstrument.InstrumentPlayer?.AttachedEntity is not {} originPlayer)
+            || originInstrument.InstrumentPlayer is not {} originPlayer)
             return Array.Empty<(NetEntity, string)>();
 
         // It's probably faster to get all possible active instruments than all entities in range
@@ -247,7 +246,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
                 continue;
 
             // We want to use the instrument player's name.
-            if (instrument.InstrumentPlayer?.AttachedEntity is not {} playerUid)
+            if (instrument.InstrumentPlayer is not {} playerUid)
                 continue;
 
             // Maybe a bit expensive but oh well GetBands is queued and has a timer anyway.
@@ -298,7 +297,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
             return;
 
         if (!instrument.Playing
-            || args.SenderSession != instrument.InstrumentPlayer
+            || args.SenderSession.AttachedEntity != instrument.InstrumentPlayer
             || instrument.InstrumentPlayer == null
             || args.SenderSession.AttachedEntity is not { } attached)
         {
@@ -374,8 +373,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
                 var entity = GetEntity(request.Entity);
 
                 var nearby = GetBands(entity);
-                _bui.TrySendUiMessage(entity, request.UiKey, new InstrumentBandResponseBuiMessage(nearby),
+                _bui.ServerSendUiMessage(entity, request.UiKey, new InstrumentBandResponseBuiMessage(nearby), request.Actor);
-                    request.Session);
             }
 
             _bandRequestQueue.Clear();
@@ -413,7 +411,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
                 (instrument.BatchesDropped >= MaxMidiBatchesDropped
                  || instrument.LaggedBatches >= MaxMidiLaggedBatches))
             {
-                if (instrument.InstrumentPlayer?.AttachedEntity is {Valid: true} mob)
+                if (instrument.InstrumentPlayer is {Valid: true} mob)
                 {
                     _stuns.TryParalyze(mob, TimeSpan.FromSeconds(1), true);
 
@@ -423,7 +421,7 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
 
                 // Just in case
                 Clean(uid);
-                _bui.TryCloseAll(uid, InstrumentUiKey.Key);
+                _bui.CloseUi(uid, InstrumentUiKey.Key);
             }
 
             instrument.Timer += frameTime;
@@ -437,13 +435,12 @@ public sealed partial class InstrumentSystem : SharedInstrumentSystem
         }
     }
 
-    public void ToggleInstrumentUi(EntityUid uid, ICommonSession session, InstrumentComponent? component = null)
+    public void ToggleInstrumentUi(EntityUid uid, EntityUid actor, InstrumentComponent? component = null)
     {
         if (!Resolve(uid, ref component))
             return;
 
-        if (_bui.TryGetUi(uid, InstrumentUiKey.Key, out var bui))
+        _bui.TryToggleUi(uid, InstrumentUiKey.Key, actor);
-            _bui.ToggleUi(bui, session);
     }
 
     public override bool ResolveInstrument(EntityUid uid, ref SharedInstrumentComponent? component)

Content.Server/Interaction/InteractionSystem.cs

@@ -16,13 +16,6 @@ namespace Content.Server.Interaction
         [Dependency] private readonly SharedContainerSystem _container = default!;
         [Dependency] private readonly UserInterfaceSystem _uiSystem = default!;
 
-        public override void Initialize()
-        {
-            base.Initialize();
-
-            SubscribeLocalEvent<BoundUserInterfaceCheckRangeEvent>(HandleUserInterfaceRangeCheck);
-        }
-
         public override bool CanAccessViaStorage(EntityUid user, EntityUid target)
         {
             if (Deleted(target))
@@ -37,26 +30,8 @@ namespace Content.Server.Interaction
             if (storage.Container?.ID != container.ID)
                 return false;
 
-            if (!TryComp(user, out ActorComponent? actor))
-                return false;
-
             // we don't check if the user can access the storage entity itself. This should be handed by the UI system.
-            return _uiSystem.SessionHasOpenUi(container.Owner, StorageComponent.StorageUiKey.Key, actor.PlayerSession);
+            return _uiSystem.IsUiOpen(container.Owner, StorageComponent.StorageUiKey.Key, user);
-        }
-
-        private void HandleUserInterfaceRangeCheck(ref BoundUserInterfaceCheckRangeEvent ev)
-        {
-            if (ev.Player.AttachedEntity is not { } user || ev.Result == BoundUserInterfaceRangeResult.Fail)
-                return;
-
-            if (InRangeUnobstructed(user, ev.Target, ev.UserInterface.InteractionRange))
-            {
-                ev.Result = BoundUserInterfaceRangeResult.Pass;
-            }
-            else
-            {
-                ev.Result = BoundUserInterfaceRangeResult.Fail;
-            }
         }
     }
 }

Content.Server/Kitchen/EntitySystems/MicrowaveSystem.cs

@@ -79,7 +79,7 @@ namespace Content.Server.Kitchen.EntitySystems
 
             SubscribeLocalEvent<MicrowaveComponent, SignalReceivedEvent>(OnSignalReceived);
 
-            SubscribeLocalEvent<MicrowaveComponent, MicrowaveStartCookMessage>((u, c, m) => Wzhzhzh(u, c, m.Session.AttachedEntity));
+            SubscribeLocalEvent<MicrowaveComponent, MicrowaveStartCookMessage>((u, c, m) => Wzhzhzh(u, c, m.Actor));
             SubscribeLocalEvent<MicrowaveComponent, MicrowaveEjectMessage>(OnEjectMessage);
             SubscribeLocalEvent<MicrowaveComponent, MicrowaveEjectSolidIndexedMessage>(OnEjectIndex);
             SubscribeLocalEvent<MicrowaveComponent, MicrowaveSelectCookTimeMessage>(OnSelectTime);
@@ -355,11 +355,7 @@ namespace Content.Server.Kitchen.EntitySystems
 
         public void UpdateUserInterfaceState(EntityUid uid, MicrowaveComponent component)
         {
-            var ui = _userInterface.GetUiOrNull(uid, MicrowaveUiKey.Key);
+            _userInterface.SetUiState(uid, MicrowaveUiKey.Key, new MicrowaveUpdateUserInterfaceState(
-            if (ui == null)
-                return;
-
-            _userInterface.SetUiState(ui, new MicrowaveUpdateUserInterfaceState(
                 GetNetEntityArray(component.Storage.ContainedEntities.ToArray()),
                 HasComp<ActiveMicrowaveComponent>(uid),
                 component.CurrentCookTimeButtonIndex,

Content.Server/Kitchen/EntitySystems/ReagentGrinderSystem.cs

@@ -127,7 +127,7 @@ namespace Content.Server.Kitchen.EntitySystems
                     _solutionContainersSystem.TryAddSolution(containerSoln.Value, solution);
                 }
 
-                _userInterfaceSystem.TrySendUiMessage(uid, ReagentGrinderUiKey.Key,
+                _userInterfaceSystem.ServerSendUiMessage(uid, ReagentGrinderUiKey.Key,
                     new ReagentGrinderWorkCompleteMessage());
 
                 UpdateUiState(uid);
@@ -228,7 +228,7 @@ namespace Content.Server.Kitchen.EntitySystems
                 GetNetEntityArray(inputContainer.ContainedEntities.ToArray()),
                 containerSolution?.Contents.ToArray()
             );
-            _userInterfaceSystem.TrySetUiState(uid, ReagentGrinderUiKey.Key, state);
+            _userInterfaceSystem.SetUiState(uid, ReagentGrinderUiKey.Key, state);
         }
 
         private void OnStartMessage(Entity<ReagentGrinderComponent> entity, ref ReagentGrinderStartMessage message)
@@ -305,7 +305,7 @@ namespace Content.Server.Kitchen.EntitySystems
 
             reagentGrinder.AudioStream = _audioSystem.PlayPvs(sound, uid,
                 AudioParams.Default.WithPitchScale(1 / reagentGrinder.WorkTimeMultiplier)).Value.Entity; //slightly higher pitched
-            _userInterfaceSystem.TrySendUiMessage(uid, ReagentGrinderUiKey.Key,
+            _userInterfaceSystem.ServerSendUiMessage(uid, ReagentGrinderUiKey.Key,
                 new ReagentGrinderWorkStartedMessage(program));
         }
 

Content.Server/Labels/Label/HandLabelerSystem.cs

@@ -90,7 +90,7 @@ namespace Content.Server.Labels
 
         private void OnHandLabelerLabelChanged(EntityUid uid, HandLabelerComponent handLabeler, HandLabelerLabelChangedMessage args)
         {
-            if (args.Session.AttachedEntity is not {Valid: true} player)
+            if (args.Actor is not {Valid: true} player)
                 return;
 
             var label = args.Label.Trim();
@@ -109,7 +109,7 @@ namespace Content.Server.Labels
             if (!Resolve(uid, ref handLabeler))
                 return;
 
-            _userInterfaceSystem.TrySetUiState(uid, HandLabelerUiKey.Key,
+            _userInterfaceSystem.SetUiState(uid, HandLabelerUiKey.Key,
                 new HandLabelerBoundUserInterfaceState(handLabeler.AssignedLabel));
         }
     }

Content.Server/Lathe/LatheSystem.cs

@@ -226,11 +226,10 @@ namespace Content.Server.Lathe
             if (!Resolve(uid, ref component))
                 return;
 
-            var ui = _uiSys.GetUi(uid, LatheUiKey.Key);
             var producing = component.CurrentRecipe ?? component.Queue.FirstOrDefault();
 
             var state = new LatheUpdateState(GetAvailableRecipes(uid, component), component.Queue, producing);
-            _uiSys.SetUiState(ui, state);
+            _uiSys.SetUiState(uid, LatheUiKey.Key, state);
         }
 
         private void OnGetRecipes(EntityUid uid, TechnologyDatabaseComponent component, LatheGetRecipesEvent args)
@@ -337,10 +336,10 @@ namespace Content.Server.Lathe
                     else
                         break;
                 }
-                if (count > 0 && args.Session.AttachedEntity != null)
+                if (count > 0)
                 {
                     _adminLogger.Add(LogType.Action, LogImpact.Low,
-                        $"{ToPrettyString(args.Session.AttachedEntity.Value):player} queued {count} {recipe.Name} at {ToPrettyString(uid):lathe}");
+                        $"{ToPrettyString(args.Actor):player} queued {count} {recipe.Name} at {ToPrettyString(uid):lathe}");
                 }
             }
             TryStartProducing(uid, component);

Content.Server/Lock/EntitySystems/ActivatableUIRequiresLockSystem.cs

@@ -3,6 +3,7 @@ using Content.Server.Popups;
 using Content.Shared.UserInterface;
 using Content.Shared.Lock;
 using Content.Server.UserInterface;
+using ActivatableUISystem = Content.Shared.UserInterface.ActivatableUISystem;
 
 namespace Content.Server.Lock.EntitySystems;
 public sealed class ActivatableUIRequiresLockSystem : EntitySystem

Content.Server/MagicMirror/MagicMirrorSystem.cs

@@ -32,7 +32,7 @@ public sealed class MagicMirrorSystem : EntitySystem
 
         Subs.BuiEvents<MagicMirrorComponent>(MagicMirrorUiKey.Key, subs =>
         {
-            subs.Event<BoundUIClosedEvent>(OnUIClosed);
+            subs.Event<BoundUIClosedEvent>(OnUiClosed);
             subs.Event<MagicMirrorSelectMessage>(OnMagicMirrorSelect);
             subs.Event<MagicMirrorChangeColorMessage>(OnTryMagicMirrorChangeColor);
             subs.Event<MagicMirrorAddSlotMessage>(OnTryMagicMirrorAddSlot);
@@ -62,10 +62,7 @@ public sealed class MagicMirrorSystem : EntitySystem
         if (!args.CanReach || args.Target == null)
             return;
 
-        if (!TryComp<ActorComponent>(args.User, out var actor))
+        if (!_uiSystem.TryOpenUi(mirror.Owner, MagicMirrorUiKey.Key, args.User))
-            return;
-
-        if (!_uiSystem.TryOpen(mirror.Owner, MagicMirrorUiKey.Key, actor.PlayerSession))
             return;
 
         UpdateInterface(mirror.Owner, args.Target.Value, mirror.Comp);
@@ -79,7 +76,7 @@ public sealed class MagicMirrorSystem : EntitySystem
 
     private void OnMagicMirrorSelect(EntityUid uid, MagicMirrorComponent component, MagicMirrorSelectMessage message)
     {
-        if (component.Target is not { } target || message.Session.AttachedEntity is not { } user)
+        if (component.Target is not { } target)
             return;
 
         _doAfterSystem.Cancel(component.DoAfter);
@@ -92,7 +89,7 @@ public sealed class MagicMirrorSystem : EntitySystem
             Marking = message.Marking,
         };
 
-        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, user, component.SelectSlotTime, doAfter, uid, target: target, used: uid)
+        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, message.Actor, component.SelectSlotTime, doAfter, uid, target: target, used: uid)
         {
             DistanceThreshold = SharedInteractionSystem.InteractionRange,
             BreakOnDamage = true,
@@ -134,7 +131,7 @@ public sealed class MagicMirrorSystem : EntitySystem
 
     private void OnTryMagicMirrorChangeColor(EntityUid uid, MagicMirrorComponent component, MagicMirrorChangeColorMessage message)
     {
-        if (component.Target is not { } target || message.Session.AttachedEntity is not { } user)
+        if (component.Target is not { } target)
             return;
 
         _doAfterSystem.Cancel(component.DoAfter);
@@ -147,7 +144,7 @@ public sealed class MagicMirrorSystem : EntitySystem
             Colors = message.Colors,
         };
 
-        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, user, component.ChangeSlotTime, doAfter, uid, target: target, used: uid)
+        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, message.Actor, component.ChangeSlotTime, doAfter, uid, target: target, used: uid)
         {
             BreakOnDamage = true,
             BreakOnMove = true,
@@ -187,7 +184,7 @@ public sealed class MagicMirrorSystem : EntitySystem
 
     private void OnTryMagicMirrorRemoveSlot(EntityUid uid, MagicMirrorComponent component, MagicMirrorRemoveSlotMessage message)
     {
-        if (component.Target is not { } target || message.Session.AttachedEntity is not { } user)
+        if (component.Target is not { } target)
             return;
 
         _doAfterSystem.Cancel(component.DoAfter);
@@ -199,7 +196,7 @@ public sealed class MagicMirrorSystem : EntitySystem
             Slot = message.Slot,
         };
 
-        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, user, component.RemoveSlotTime, doAfter, uid, target: target, used: uid)
+        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, message.Actor, component.RemoveSlotTime, doAfter, uid, target: target, used: uid)
         {
             DistanceThreshold = SharedInteractionSystem.InteractionRange,
             BreakOnDamage = true,
@@ -243,9 +240,6 @@ public sealed class MagicMirrorSystem : EntitySystem
         if (component.Target == null)
             return;
 
-        if (message.Session.AttachedEntity == null)
-            return;
-
         _doAfterSystem.Cancel(component.DoAfter);
         component.DoAfter = null;
 
@@ -254,7 +248,7 @@ public sealed class MagicMirrorSystem : EntitySystem
             Category = message.Category,
         };
 
-        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, message.Session.AttachedEntity.Value, component.AddSlotTime, doAfter, uid, target: component.Target.Value, used: uid)
+        _doAfterSystem.TryStartDoAfter(new DoAfterArgs(EntityManager, message.Actor, component.AddSlotTime, doAfter, uid, target: component.Target.Value, used: uid)
         {
             BreakOnDamage = true,
             BreakOnMove = true,
@@ -316,10 +310,10 @@ public sealed class MagicMirrorSystem : EntitySystem
             humanoid.MarkingSet.PointsLeft(MarkingCategories.FacialHair) + facialHair.Count);
 
         component.Target = targetUid;
-        _uiSystem.TrySetUiState(mirrorUid, MagicMirrorUiKey.Key, state);
+        _uiSystem.SetUiState(mirrorUid, MagicMirrorUiKey.Key, state);
     }
 
-    private void OnUIClosed(Entity<MagicMirrorComponent> ent, ref BoundUIClosedEvent args)
+    private void OnUiClosed(Entity<MagicMirrorComponent> ent, ref BoundUIClosedEvent args)
     {
         ent.Comp.Target = null;
     }

Content.Server/MassMedia/Systems/NewsSystem.cs

@@ -92,15 +92,12 @@ public sealed class NewsSystem : SharedNewsSystem
         if (msg.ArticleNum >= articles.Count)
             return;
 
-        if (msg.Session.AttachedEntity is not { } actor)
-            return;
-
         var article = articles[msg.ArticleNum];
-        if (CheckDeleteAccess(article, ent, actor))
+        if (CheckDeleteAccess(article, ent, msg.Actor))
         {
             _adminLogger.Add(
                 LogType.Chat, LogImpact.Medium,
-                $"{ToPrettyString(actor):actor} deleted news article {article.Title} by {article.Author}: {article.Content}"
+                $"{ToPrettyString(msg.Actor):actor} deleted news article {article.Title} by {article.Author}: {article.Content}"
                 );
 
             articles.RemoveAt(msg.ArticleNum);
@@ -138,14 +135,11 @@ public sealed class NewsSystem : SharedNewsSystem
         if (!TryGetArticles(ent, out var articles))
             return;
 
-        if (msg.Session.AttachedEntity is not { } author)
+        if (!_accessReader.FindStationRecordKeys(msg.Actor, out _))
-            return;
-
-        if (!_accessReader.FindStationRecordKeys(author, out _))
             return;
 
         string? authorName = null;
-        if (_idCardSystem.TryFindIdCard(author, out var idCard))
+        if (_idCardSystem.TryFindIdCard(msg.Actor, out var idCard))
             authorName = idCard.Comp.FullName;
 
         var title = msg.Title.Trim();
@@ -164,7 +158,7 @@ public sealed class NewsSystem : SharedNewsSystem
         _adminLogger.Add(
             LogType.Chat,
             LogImpact.Medium,
-            $"{ToPrettyString(author):actor} created news article {article.Title} by {article.Author}: {article.Content}"
+            $"{ToPrettyString(msg.Actor):actor} created news article {article.Title} by {article.Author}: {article.Content}"
             );
 
         articles.Add(article);
@@ -248,14 +242,14 @@ public sealed class NewsSystem : SharedNewsSystem
 
     private void UpdateWriterUi(Entity<NewsWriterComponent> ent)
     {
-        if (!_ui.TryGetUi(ent, NewsWriterUiKey.Key, out var ui))
+        if (!_ui.HasUi(ent, NewsWriterUiKey.Key))
             return;
 
         if (!TryGetArticles(ent, out var articles))
             return;
 
         var state = new NewsWriterBoundUserInterfaceState(articles.ToArray(), ent.Comp.PublishEnabled, ent.Comp.NextPublish);
-        _ui.SetUiState(ui, state);
+        _ui.SetUiState(ent.Owner, NewsWriterUiKey.Key, state);
     }
 
     private void UpdateReaderUi(Entity<NewsReaderCartridgeComponent> ent, EntityUid loaderUid)

Content.Server/Mech/Systems/MechSystem.cs

@@ -303,15 +303,14 @@ public sealed partial class MechSystem : SharedMechSystem
         {
             EquipmentStates = ev.States
         };
-        var ui = _ui.GetUi(uid, MechUiKey.Key);
+        _ui.SetUiState(uid, MechUiKey.Key, state);
-        _ui.SetUiState(ui, state);
     }
 
     public override void BreakMech(EntityUid uid, MechComponent? component = null)
     {
         base.BreakMech(uid, component);
 
-        _ui.TryCloseAll(uid, MechUiKey.Key);
+        _ui.CloseUi(uid, MechUiKey.Key);
         _actionBlocker.UpdateCanMove(uid);
     }
 

Content.Server/Medical/CrewMonitoring/CrewMonitoringConsoleSystem.cs

@@ -58,7 +58,7 @@ public sealed class CrewMonitoringConsoleSystem : EntitySystem
         if (!Resolve(uid, ref component))
             return;
 
-        if (!_uiSystem.TryGetUi(uid, CrewMonitoringUIKey.Key, out var bui))
+        if (!_uiSystem.IsUiOpen(uid, CrewMonitoringUIKey.Key))
             return;
 
         // The grid must have a NavMapComponent to visualize the map in the UI
@@ -69,6 +69,6 @@ public sealed class CrewMonitoringConsoleSystem : EntitySystem
 
         // Update all sensors info
         var allSensors = component.ConnectedSensors.Values.ToList();
-        _uiSystem.SetUiState(bui, new CrewMonitoringState(allSensors));
+        _uiSystem.SetUiState(uid, CrewMonitoringUIKey.Key, new CrewMonitoringState(allSensors));
     }
 }

Content.Server/Medical/CryoPodSystem.cs

@@ -193,7 +193,8 @@ public sealed partial class CryoPodSystem : SharedCryoPodSystem
             healthAnalyzer.ScannedEntity = entity.Comp.BodyContainer.ContainedEntity;
         }
 
-        _userInterfaceSystem.TrySendUiMessage(
+        // TODO: This should be a state my dude
+        _userInterfaceSystem.ServerSendUiMessage(
             entity.Owner,
             HealthAnalyzerUiKey.Key,
             new HealthAnalyzerScannedUserMessage(GetNetEntity(entity.Comp.BodyContainer.ContainedEntity),
@@ -246,7 +247,7 @@ public sealed partial class CryoPodSystem : SharedCryoPodSystem
         else
         {
             RemComp<ActiveCryoPodComponent>(entity);
-            _uiSystem.TryCloseAll(entity.Owner, HealthAnalyzerUiKey.Key);
+            _uiSystem.CloseUi(entity.Owner, HealthAnalyzerUiKey.Key);
         }
         UpdateAppearance(entity.Owner, entity.Comp);
     }
@@ -297,7 +298,7 @@ public sealed partial class CryoPodSystem : SharedCryoPodSystem
         }
 
         // if body is ejected - no need to display health-analyzer
-        _uiSystem.TryCloseAll(cryoPod.Owner, HealthAnalyzerUiKey.Key);
+        _uiSystem.CloseUi(cryoPod.Owner, HealthAnalyzerUiKey.Key);
     }
 
     #endregion

Content.Server/Medical/HealthAnalyzerSystem.cs

@@ -128,10 +128,10 @@ public sealed class HealthAnalyzerSystem : EntitySystem
 
     private void OpenUserInterface(EntityUid user, EntityUid analyzer)
     {
-        if (!TryComp<ActorComponent>(user, out var actor) || !_uiSystem.TryGetUi(analyzer, HealthAnalyzerUiKey.Key, out var ui))
+        if (!_uiSystem.HasUi(analyzer, HealthAnalyzerUiKey.Key))
             return;
 
-        _uiSystem.OpenUi(ui, actor.PlayerSession);
+        _uiSystem.OpenUi(analyzer, HealthAnalyzerUiKey.Key, user);
     }
 
     /// <summary>
@@ -172,7 +172,7 @@ public sealed class HealthAnalyzerSystem : EntitySystem
     /// <param name="scanMode">True makes the UI show ACTIVE, False makes the UI show INACTIVE</param>
     public void UpdateScannedUser(EntityUid healthAnalyzer, EntityUid target, bool scanMode)
     {
-        if (!_uiSystem.TryGetUi(healthAnalyzer, HealthAnalyzerUiKey.Key, out var ui))
+        if (!_uiSystem.HasUi(healthAnalyzer, HealthAnalyzerUiKey.Key))
             return;
 
         if (!HasComp<DamageableComponent>(target))
@@ -194,9 +194,7 @@ public sealed class HealthAnalyzerSystem : EntitySystem
             bleeding = bloodstream.BleedAmount > 0;
         }
 
-
+        _uiSystem.ServerSendUiMessage(healthAnalyzer, HealthAnalyzerUiKey.Key, new HealthAnalyzerScannedUserMessage(
-
-        _uiSystem.SendUiMessage(ui, new HealthAnalyzerScannedUserMessage(
             GetNetEntity(target),
             bodyTemperature,
             bloodAmount,

Content.Server/Nuke/NukeSystem.cs

@@ -187,7 +187,7 @@ public sealed class NukeSystem : EntitySystem
                     continue;
 
                 var msg = Loc.GetString("nuke-component-cant-anchor-floor");
-                _popups.PopupEntity(msg, uid, args.Session, PopupType.MediumCaution);
+                _popups.PopupEntity(msg, uid, args.Actor, PopupType.MediumCaution);
 
                 return;
             }
@@ -243,10 +243,7 @@ public sealed class NukeSystem : EntitySystem
 
         else
         {
-            if (args.Session.AttachedEntity is not { } user)
+            DisarmBombDoafter(uid, args.Actor, component);
-                return;
-
-            DisarmBombDoafter(uid, user, component);
         }
     }
 
@@ -366,8 +363,7 @@ public sealed class NukeSystem : EntitySystem
         if (!Resolve(uid, ref component))
             return;
 
-        var ui = _ui.GetUiOrNull(uid, NukeUiKey.Key);
+        if (!_ui.HasUi(uid, NukeUiKey.Key))
-        if (ui == null)
             return;
 
         var anchored = Transform(uid).Anchored;
@@ -388,7 +384,7 @@ public sealed class NukeSystem : EntitySystem
             CooldownTime = (int) component.CooldownTime
         };
 
-        _ui.SetUiState(ui, state);
+        _ui.SetUiState(uid, NukeUiKey.Key, state);
     }
 
     private void PlayNukeKeypadSound(EntityUid uid, int number, NukeComponent? component = null)

Content.Server/NukeOps/WarDeclaratorSystem.cs

@@ -55,9 +55,6 @@ public sealed class WarDeclaratorSystem : EntitySystem
 
     private void OnActivated(Entity<WarDeclaratorComponent> ent, ref WarDeclaratorActivateMessage args)
     {
-        if (args.Session.AttachedEntity is not {} playerEntity)
-            return;
-
         var ev = new WarDeclaredEvent(ent.Comp.CurrentStatus, ent);
         RaiseLocalEvent(ref ev);
 
@@ -75,7 +72,7 @@ public sealed class WarDeclaratorSystem : EntitySystem
         {
             var title = Loc.GetString(ent.Comp.SenderTitle);
             _chat.DispatchGlobalAnnouncement(ent.Comp.Message, title, true, ent.Comp.Sound, ent.Comp.Color);
-            _adminLogger.Add(LogType.Chat, LogImpact.Low, $"{ToPrettyString(playerEntity):player} has declared war with this text: {ent.Comp.Message}");
+            _adminLogger.Add(LogType.Chat, LogImpact.Low, $"{ToPrettyString(args.Actor):player} has declared war with this text: {ent.Comp.Message}");
         }
 
         UpdateUI(ent, ev.Status);
@@ -83,8 +80,8 @@ public sealed class WarDeclaratorSystem : EntitySystem
 
     private void UpdateUI(Entity<WarDeclaratorComponent> ent, WarConditionStatus? status = null)
     {
-        _userInterfaceSystem.TrySetUiState(
+        _userInterfaceSystem.SetUiState(
-            ent,
+            ent.Owner,
             WarDeclaratorUiKey.Key,
             new WarDeclaratorBoundUserInterfaceState(status, ent.Comp.DisableAt, ent.Comp.ShuttleDisabledTime));
     }

Content.Server/PAI/PAISystem.cs

@@ -102,13 +102,15 @@ public sealed class PAISystem : SharedPAISystem
     {
         //  Close the instrument interface if it was open
         //  before closing
-        if (HasComp<ActiveInstrumentComponent>(uid) && TryComp<ActorComponent>(uid, out var actor))
+        if (HasComp<ActiveInstrumentComponent>(uid))
         {
-            _instrumentSystem.ToggleInstrumentUi(uid, actor.PlayerSession);
+            _instrumentSystem.ToggleInstrumentUi(uid, uid);
         }
 
         //  Stop instrument
-        if (TryComp<InstrumentComponent>(uid, out var instrument)) _instrumentSystem.Clean(uid, instrument);
+        if (TryComp<InstrumentComponent>(uid, out var instrument))
+            _instrumentSystem.Clean(uid, instrument);
+
         if (TryComp<MetaDataComponent>(uid, out var metadata))
         {
             var proto = metadata.EntityPrototype;

Content.Server/PDA/PdaSystem.cs

@@ -41,6 +41,7 @@ namespace Content.Server.PDA
             SubscribeLocalEvent<PdaComponent, LightToggleEvent>(OnLightToggle);
 
             // UI Events:
+            SubscribeLocalEvent<PdaComponent, BoundUIOpenedEvent>(OnPdaOpen);
             SubscribeLocalEvent<PdaComponent, PdaRequestUpdateInterfaceMessage>(OnUiMessage);
             SubscribeLocalEvent<PdaComponent, PdaToggleFlashlightMessage>(OnUiMessage);
             SubscribeLocalEvent<PdaComponent, PdaShowRingtoneMessage>(OnUiMessage);
@@ -145,7 +146,7 @@ namespace Content.Server.PDA
             if (!Resolve(uid, ref pda, false))
                 return;
 
-            if (!_ui.TryGetUi(uid, PdaUiKey.Key, out var ui))
+            if (!_ui.HasUi(uid, PdaUiKey.Key))
                 return;
 
             var address = GetDeviceNetAddress(uid);
@@ -182,7 +183,15 @@ namespace Content.Server.PDA
                 hasInstrument,
                 address);
 
-            _ui.SetUiState(ui, state);
+            _ui.SetUiState(uid, PdaUiKey.Key, state);
+        }
+
+        private void OnPdaOpen(Entity<PdaComponent> ent, ref BoundUIOpenedEvent args)
+        {
+            if (!PdaUiKey.Key.Equals(args.UiKey))
+                return;
+
+            UpdatePdaUi(ent.Owner, ent.Comp);
         }
 
         private void OnUiMessage(EntityUid uid, PdaComponent pda, PdaRequestUpdateInterfaceMessage msg)
@@ -208,7 +217,7 @@ namespace Content.Server.PDA
                 return;
 
             if (HasComp<RingerComponent>(uid))
-                _ringer.ToggleRingerUI(uid, msg.Session);
+                _ringer.ToggleRingerUI(uid, msg.Actor);
         }
 
         private void OnUiMessage(EntityUid uid, PdaComponent pda, PdaShowMusicMessage msg)
@@ -217,7 +226,7 @@ namespace Content.Server.PDA
                 return;
 
             if (TryComp<InstrumentComponent>(uid, out var instrument))
-                _instrument.ToggleInstrumentUi(uid, msg.Session, instrument);
+                _instrument.ToggleInstrumentUi(uid, msg.Actor, instrument);
         }
 
         private void OnUiMessage(EntityUid uid, PdaComponent pda, PdaShowUplinkMessage msg)
@@ -227,7 +236,7 @@ namespace Content.Server.PDA
 
             // check if its locked again to prevent malicious clients opening locked uplinks
             if (TryComp<StoreComponent>(uid, out var store) && IsUnlocked(uid))
-                _store.ToggleUi(msg.Session.AttachedEntity!.Value, uid, store);
+                _store.ToggleUi(msg.Actor, uid, store);
         }
 
         private void OnUiMessage(EntityUid uid, PdaComponent pda, PdaLockUplinkMessage msg)

Content.Server/PDA/Ringer/RingerSystem.cs

@@ -81,7 +81,10 @@ namespace Content.Server.PDA.Ringer
 
         private void OnSetRingtone(EntityUid uid, RingerComponent ringer, RingerSetRingtoneMessage args)
         {
-            ref var lastSetAt = ref CollectionsMarshal.GetValueRefOrAddDefault(_lastSetRingtoneAt, args.Session.UserId, out var exists);
+            if (!TryComp(args.Actor, out ActorComponent? actorComp))
+                return;
+
+            ref var lastSetAt = ref CollectionsMarshal.GetValueRefOrAddDefault(_lastSetRingtoneAt, actorComp.PlayerSession.UserId, out var exists);
 
             // Delay on the client is 0.333, 0.25 is still enough and gives some leeway in case of small time differences
             if (exists && lastSetAt > _gameTiming.CurTime - TimeSpan.FromMilliseconds(250))
@@ -111,7 +114,7 @@ namespace Content.Server.PDA.Ringer
 
                 // can't keep store open after locking it
                 if (!uplink.Unlocked)
-                    _ui.TryCloseAll(uid, StoreUiKey.Key);
+                    _ui.CloseUi(uid, StoreUiKey.Key);
 
                 // no saving the code to prevent meta click set on sus guys pda -> wewlad
                 args.Handled = true;
@@ -130,7 +133,7 @@ namespace Content.Server.PDA.Ringer
                 return;
 
             uplink.Unlocked = false;
-            _ui.TryCloseAll(uid, StoreUiKey.Key);
+            _ui.CloseUi(uid, StoreUiKey.Key);
         }
 
         public void RandomizeRingtone(EntityUid uid, RingerComponent ringer, MapInitEvent args)
@@ -181,14 +184,12 @@ namespace Content.Server.PDA.Ringer
 
         private void UpdateRingerUserInterface(EntityUid uid, RingerComponent ringer, bool isPlaying)
         {
-            if (_ui.TryGetUi(uid, RingerUiKey.Key, out var bui))
+            _ui.SetUiState(uid, RingerUiKey.Key, new RingerUpdateState(isPlaying, ringer.Ringtone));
-                _ui.SetUiState(bui, new RingerUpdateState(isPlaying, ringer.Ringtone));
         }
 
-        public bool ToggleRingerUI(EntityUid uid, ICommonSession session)
+        public bool ToggleRingerUI(EntityUid uid, EntityUid actor)
         {
-            if (_ui.TryGetUi(uid, RingerUiKey.Key, out var bui))
+            _ui.TryToggleUi(uid, RingerUiKey.Key, actor);
-                _ui.ToggleUi(bui, session);
             return true;
         }
 

Content.Server/Paper/PaperComponent.cs

@@ -3,7 +3,7 @@ using Robust.Shared.GameStates;
 
 namespace Content.Server.Paper;
 
-[NetworkedComponent, RegisterComponent]
+[RegisterComponent]
 public sealed partial class PaperComponent : SharedPaperComponent
 {
     public PaperAction Mode;

Content.Server/Paper/PaperSystem.cs

@@ -67,11 +67,7 @@ namespace Content.Server.Paper
         private void BeforeUIOpen(EntityUid uid, PaperComponent paperComp, BeforeActivatableUIOpenEvent args)
         {
             paperComp.Mode = PaperAction.Read;
-
+            UpdateUserInterface(uid, paperComp);
-            if (!TryComp<ActorComponent>(args.User, out var actor))
-                return;
-
-            UpdateUserInterface(uid, paperComp, actor.PlayerSession);
         }
 
         private void OnExamined(EntityUid uid, PaperComponent paperComp, ExaminedEvent args)
@@ -108,12 +104,10 @@ namespace Content.Server.Paper
             {
                 var writeEvent = new PaperWriteEvent(uid, args.User);
                 RaiseLocalEvent(args.Used, ref writeEvent);
-                if (!TryComp<ActorComponent>(args.User, out var actor))
-                    return;
 
                 paperComp.Mode = PaperAction.Write;
-                _uiSystem.TryOpen(uid, PaperUiKey.Key, actor.PlayerSession);
+                _uiSystem.OpenUi(uid, PaperUiKey.Key, args.User);
-                UpdateUserInterface(uid, paperComp, actor.PlayerSession);
+                UpdateUserInterface(uid, paperComp);
                 args.Handled = true;
                 return;
             }
@@ -157,9 +151,8 @@ namespace Content.Server.Paper
                 if (TryComp<MetaDataComponent>(uid, out var meta))
                     _metaSystem.SetEntityDescription(uid, "", meta);
 
-                if (args.Session.AttachedEntity != null)
+                _adminLogger.Add(LogType.Chat, LogImpact.Low,
-                    _adminLogger.Add(LogType.Chat, LogImpact.Low,
+                    $"{ToPrettyString(args.Actor):player} has written on {ToPrettyString(uid):entity} the following text: {args.Text}");
-                        $"{ToPrettyString(args.Session.AttachedEntity.Value):player} has written on {ToPrettyString(uid):entity} the following text: {args.Text}");
 
                 _audio.PlayPvs(paperComp.Sound, uid);
             }
@@ -213,13 +206,12 @@ namespace Content.Server.Paper
             _appearance.SetData(uid, PaperVisuals.Status, status, appearance);
         }
 
-        public void UpdateUserInterface(EntityUid uid, PaperComponent? paperComp = null, ICommonSession? session = null)
+        public void UpdateUserInterface(EntityUid uid, PaperComponent? paperComp = null)
         {
             if (!Resolve(uid, ref paperComp))
                 return;
 
-            if (_uiSystem.TryGetUi(uid, PaperUiKey.Key, out var bui))
+            _uiSystem.SetUiState(uid, PaperUiKey.Key, new PaperBoundUserInterfaceState(paperComp.Content, paperComp.StampedBy, paperComp.Mode));
-                _uiSystem.SetUiState(bui, new PaperBoundUserInterfaceState(paperComp.Content, paperComp.StampedBy, paperComp.Mode), session);
         }
     }
 

Content.Server/ParticleAccelerator/EntitySystems/ParticleAcceleratorSystem.ControlBox.cs

@@ -67,7 +67,7 @@ public sealed partial class ParticleAcceleratorSystem
         FireEmitter(comp.StarboardEmitter!.Value, strength);
     }
 
-    public void SwitchOn(EntityUid uid, ICommonSession? user = null, ParticleAcceleratorControlBoxComponent? comp = null)
+    public void SwitchOn(EntityUid uid, EntityUid? user = null, ParticleAcceleratorControlBoxComponent? comp = null)
     {
         if (!Resolve(uid, ref comp))
             return;
@@ -77,7 +77,7 @@ public sealed partial class ParticleAcceleratorSystem
         if (comp.Enabled || !comp.CanBeEnabled)
             return;
 
-        if (user?.AttachedEntity is { } player)
+        if (user is { } player)
             _adminLogger.Add(LogType.Action, LogImpact.Low, $"{ToPrettyString(player):player} has turned {ToPrettyString(uid)} on");
 
         comp.Enabled = true;
@@ -90,14 +90,14 @@ public sealed partial class ParticleAcceleratorSystem
         UpdateUI(uid, comp);
     }
 
-    public void SwitchOff(EntityUid uid, ICommonSession? user = null, ParticleAcceleratorControlBoxComponent? comp = null)
+    public void SwitchOff(EntityUid uid, EntityUid? user = null, ParticleAcceleratorControlBoxComponent? comp = null)
     {
         if (!Resolve(uid, ref comp))
             return;
         if (!comp.Enabled)
             return;
 
-        if (user?.AttachedEntity is { } player)
+        if (user is { } player)
             _adminLogger.Add(LogType.Action, LogImpact.Low, $"{ToPrettyString(player):player} has turned {ToPrettyString(uid)} off");
 
         comp.Enabled = false;
@@ -138,7 +138,7 @@ public sealed partial class ParticleAcceleratorSystem
         UpdateUI(uid, comp);
     }
 
-    public void SetStrength(EntityUid uid, ParticleAcceleratorPowerState strength, ICommonSession? user = null, ParticleAcceleratorControlBoxComponent? comp = null)
+    public void SetStrength(EntityUid uid, ParticleAcceleratorPowerState strength, EntityUid? user = null, ParticleAcceleratorControlBoxComponent? comp = null)
     {
         if (!Resolve(uid, ref comp))
             return;
@@ -154,7 +154,7 @@ public sealed partial class ParticleAcceleratorSystem
         if (strength == comp.SelectedStrength)
             return;
 
-        if (user?.AttachedEntity is { } player)
+        if (user is { } player)
         {
             var impact = strength switch
             {
@@ -235,7 +235,8 @@ public sealed partial class ParticleAcceleratorSystem
     {
         if (!Resolve(uid, ref comp))
             return;
-        if (!_uiSystem.TryGetUi(uid, ParticleAcceleratorControlBoxUiKey.Key, out var bui))
+
+        if (!_uiSystem.HasUi(uid, ParticleAcceleratorControlBoxUiKey.Key))
             return;
 
         var draw = 0f;
@@ -247,7 +248,7 @@ public sealed partial class ParticleAcceleratorSystem
             receive = powerConsumer.ReceivedPower;
         }
 
-        _uiSystem.SetUiState(bui, new ParticleAcceleratorUIState(
+        _uiSystem.SetUiState(uid, ParticleAcceleratorControlBoxUiKey.Key, new ParticleAcceleratorUIState(
             comp.Assembled,
             comp.Enabled,
             comp.SelectedStrength,
@@ -346,7 +347,7 @@ public sealed partial class ParticleAcceleratorSystem
         UpdateAppearance(uid, comp);
 
         if (!args.Powered)
-            _uiSystem.TryCloseAll(uid, ParticleAcceleratorControlBoxUiKey.Key);
+            _uiSystem.CloseUi(uid, ParticleAcceleratorControlBoxUiKey.Key);
     }
 
     private void OnUISetEnableMessage(EntityUid uid, ParticleAcceleratorControlBoxComponent comp, ParticleAcceleratorSetEnableMessage msg)
@@ -361,10 +362,10 @@ public sealed partial class ParticleAcceleratorSystem
         if (msg.Enabled)
         {
             if (comp.Assembled)
-                SwitchOn(uid, msg.Session, comp);
+                SwitchOn(uid, msg.Actor, comp);
         }
         else
-            SwitchOff(uid, msg.Session, comp);
+            SwitchOff(uid, msg.Actor, comp);
 
         UpdateUI(uid, comp);
     }
@@ -378,7 +379,7 @@ public sealed partial class ParticleAcceleratorSystem
         if (TryComp<ApcPowerReceiverComponent>(uid, out var apcPower) && !apcPower.Powered)
             return;
 
-        SetStrength(uid, msg.State, msg.Session, comp);
+        SetStrength(uid, msg.State, msg.Actor, comp);
 
         UpdateUI(uid, comp);
     }
@@ -392,7 +393,7 @@ public sealed partial class ParticleAcceleratorSystem
         if (TryComp<ApcPowerReceiverComponent>(uid, out var apcPower) && !apcPower.Powered)
             return;
 
-        RescanParts(uid, msg.Session, comp);
+        RescanParts(uid, msg.Actor, comp);
 
         UpdateUI(uid, comp);
     }

Content.Server/ParticleAccelerator/EntitySystems/ParticleAcceleratorSystem.Parts.cs

@@ -18,7 +18,7 @@ public sealed partial class ParticleAcceleratorSystem
         SubscribeLocalEvent<ParticleAcceleratorPartComponent, PhysicsBodyTypeChangedEvent>(BodyTypeChanged);
     }
 
-    public void RescanParts(EntityUid uid, ICommonSession? user = null, ParticleAcceleratorControlBoxComponent? controller = null)
+    public void RescanParts(EntityUid uid, EntityUid? user = null, ParticleAcceleratorControlBoxComponent? controller = null)
     {
         if (!Resolve(uid, ref controller))
             return;

Content.Server/ParticleAccelerator/Wires/ParticleAcceleratorLimiterWireAction.cs

@@ -48,8 +48,7 @@ public sealed partial class ParticleAcceleratorLimiterWireAction : ComponentWire
         // Yes, it's a feature that mending this wire WON'T WORK if the strength wire is also cut.
         // Since that blocks SetStrength().
         var paSystem = EntityManager.System<ParticleAcceleratorSystem>();
-        var userSession = EntityManager.TryGetComponent<ActorComponent>(user, out var actor) ? actor.PlayerSession : null;
+        paSystem.SetStrength(wire.Owner, controller.MaxStrength, user, controller);
-        paSystem.SetStrength(wire.Owner, controller.MaxStrength, userSession, controller);
         return true;
     }
 

Content.Server/ParticleAccelerator/Wires/ParticleAcceleratorStrengthWireAction.cs

@@ -33,7 +33,6 @@ public sealed partial class ParticleAcceleratorStrengthWireAction : ComponentWir
     public override void Pulse(EntityUid user, Wire wire, ParticleAcceleratorControlBoxComponent controller)
     {
         var paSystem = EntityManager.System<ParticleAcceleratorSystem>();
-        var userSession = EntityManager.TryGetComponent<ActorComponent>(user, out var actor) ? actor.PlayerSession : null;
+        paSystem.SetStrength(wire.Owner, (ParticleAcceleratorPowerState) ((int) controller.SelectedStrength + 1), user, controller);
-        paSystem.SetStrength(wire.Owner, (ParticleAcceleratorPowerState) ((int) controller.SelectedStrength + 1), userSession, controller);
     }
 }

Content.Server/ParticleAccelerator/Wires/ParticleAcceleratorToggleWireAction.cs

@@ -23,10 +23,9 @@ public sealed partial class ParticleAcceleratorPowerWireAction : ComponentWireAc
     public override bool Cut(EntityUid user, Wire wire, ParticleAcceleratorControlBoxComponent controller)
     {
         var paSystem = EntityManager.System<ParticleAcceleratorSystem>();
-        var userSession = EntityManager.TryGetComponent<ActorComponent>(user, out var actor) ? actor.PlayerSession : null;
 
         controller.CanBeEnabled = false;
-        paSystem.SwitchOff(wire.Owner, userSession, controller);
+        paSystem.SwitchOff(wire.Owner, user, controller);
         return true;
     }
 
@@ -39,11 +38,10 @@ public sealed partial class ParticleAcceleratorPowerWireAction : ComponentWireAc
     public override void Pulse(EntityUid user, Wire wire, ParticleAcceleratorControlBoxComponent controller)
     {
         var paSystem = EntityManager.System<ParticleAcceleratorSystem>();
-        var userSession = EntityManager.TryGetComponent<ActorComponent>(user, out var actor) ? actor.PlayerSession : null;
 
         if (controller.Enabled)
-            paSystem.SwitchOff(wire.Owner, userSession, controller);
+            paSystem.SwitchOff(wire.Owner, user, controller);
         else if (controller.Assembled)
-            paSystem.SwitchOn(wire.Owner, userSession, controller);
+            paSystem.SwitchOn(wire.Owner, user, controller);
     }
 }

Content.Server/Pinpointer/NavMapSystem.cs

@@ -155,9 +155,6 @@ public sealed partial class NavMapSystem : SharedNavMapSystem
 
     private void OnConfigureMessage(Entity<ConfigurableNavMapBeaconComponent> ent, ref NavMapBeaconConfigureBuiMessage args)
     {
-        if (args.Session.AttachedEntity is not { } user)
-            return;
-
         if (!TryComp<NavMapBeaconComponent>(ent, out var beacon))
             return;
 
@@ -167,7 +164,7 @@ public sealed partial class NavMapSystem : SharedNavMapSystem
             return;
 
         _adminLog.Add(LogType.Action, LogImpact.Medium,
-            $"{ToPrettyString(user):player} configured NavMapBeacon \'{ToPrettyString(ent):entity}\' with text \'{args.Text}\', color {args.Color.ToHexNoAlpha()}, and {(args.Enabled ? "enabled" : "disabled")} it.");
+            $"{ToPrettyString(args.Actor):player} configured NavMapBeacon \'{ToPrettyString(ent):entity}\' with text \'{args.Text}\', color {args.Color.ToHexNoAlpha()}, and {(args.Enabled ? "enabled" : "disabled")} it.");
 
         if (TryComp<WarpPointComponent>(ent, out var warpPoint))
         {

Content.Server/Pinpointer/StationMapSystem.cs

@@ -24,29 +24,23 @@ public sealed class StationMapSystem : EntitySystem
 
     private void OnStationMapClosed(EntityUid uid, StationMapComponent component, BoundUIClosedEvent args)
     {
-        if (!Equals(args.UiKey, StationMapUiKey.Key) || args.Session.AttachedEntity == null)
+        if (!Equals(args.UiKey, StationMapUiKey.Key))
             return;
 
-        RemCompDeferred<StationMapUserComponent>(args.Session.AttachedEntity.Value);
+        RemCompDeferred<StationMapUserComponent>(args.Actor);
     }
 
     private void OnUserParentChanged(EntityUid uid, StationMapUserComponent component, ref EntParentChangedMessage args)
     {
-        if (TryComp<ActorComponent>(uid, out var actor))
+        _ui.CloseUi(component.Map, StationMapUiKey.Key, uid);
-        {
-            _ui.TryClose(component.Map, StationMapUiKey.Key, actor.PlayerSession);
-        }
     }
 
     private void OnStationMapOpened(EntityUid uid, StationMapComponent component, BoundUIOpenedEvent args)
     {
-        if (args.Session.AttachedEntity == null)
-            return;
-
         if (!_cell.TryUseActivatableCharge(uid))
             return;
 
-        var comp = EnsureComp<StationMapUserComponent>(args.Session.AttachedEntity.Value);
+        var comp = EnsureComp<StationMapUserComponent>(args.Actor);
         comp.Map = uid;
     }
 }

Content.Server/Power/Components/ActivatableUIRequiresPowerComponent.cs

@@ -1,8 +0,0 @@
-namespace Content.Server.Power.Components
-{
-    [RegisterComponent]
-    public sealed partial class ActivatableUIRequiresPowerComponent : Component
-    {
-    }
-}
-

Content.Server/Power/EntitySystems/ActivatableUIRequiresPowerSystem.cs

@@ -4,11 +4,12 @@ using Content.Shared.UserInterface;
 using JetBrains.Annotations;
 using Content.Shared.Wires;
 using Content.Server.UserInterface;
+using Content.Shared.Power.Components;
+using ActivatableUISystem = Content.Shared.UserInterface.ActivatableUISystem;
 
 namespace Content.Server.Power.EntitySystems;
 
-[UsedImplicitly]
+public sealed class ActivatableUIRequiresPowerSystem : EntitySystem
-internal sealed class ActivatableUIRequiresPowerSystem : EntitySystem
 {
     [Dependency] private readonly ActivatableUISystem _activatableUI = default!;
     [Dependency] private readonly SharedPopupSystem _popup = default!;

Content.Server/Power/EntitySystems/ApcSystem.cs

@@ -66,11 +66,8 @@ public sealed class ApcSystem : EntitySystem
     //Update the HasAccess var for UI to read
     private void OnBoundUiOpen(EntityUid uid, ApcComponent component, BoundUIOpenedEvent args)
     {
-        if (args.Session.AttachedEntity == null)
-            return;
-
         // TODO: this should be per-player not stored on the apc
-        component.HasAccess = _accessReader.IsAllowed(args.Session.AttachedEntity.Value, uid);
+        component.HasAccess = _accessReader.IsAllowed(args.Actor, uid);
         UpdateApcState(uid, component);
     }
 
@@ -81,21 +78,18 @@ public sealed class ApcSystem : EntitySystem
         if (attemptEv.Cancelled)
         {
             _popup.PopupCursor(Loc.GetString("apc-component-on-toggle-cancel"),
-                args.Session, PopupType.Medium);
+                args.Actor, PopupType.Medium);
             return;
         }
 
-        if (args.Session.AttachedEntity == null)
+        if (_accessReader.IsAllowed(args.Actor, uid))
-            return;
-
-        if (_accessReader.IsAllowed(args.Session.AttachedEntity.Value, uid))
         {
             ApcToggleBreaker(uid, component);
         }
         else
         {
             _popup.PopupCursor(Loc.GetString("apc-component-insufficient-access"),
-                args.Session, PopupType.Medium);
+                args.Actor, PopupType.Medium);
         }
     }
 
@@ -158,7 +152,7 @@ public sealed class ApcSystem : EntitySystem
             (int) MathF.Ceiling(battery.CurrentSupply), apc.LastExternalState,
             battery.CurrentStorage / battery.Capacity);
 
-        _ui.TrySetUiState(uid, ApcUiKey.Key, state, ui: ui);
+        _ui.SetUiState((uid, ui), ApcUiKey.Key, state);
     }
 
     private ApcChargeState CalcChargeState(EntityUid uid, PowerState.Battery battery)

Content.Server/Power/EntitySystems/PowerMonitoringConsoleSystem.cs

@@ -286,20 +286,17 @@ internal sealed partial class PowerMonitoringConsoleSystem : SharedPowerMonitori
             var query = AllEntityQuery<PowerMonitoringConsoleComponent>();
             while (query.MoveNext(out var ent, out var console))
             {
-                if (!_userInterfaceSystem.TryGetUi(ent, PowerMonitoringConsoleUiKey.Key, out var bui))
+                if (!_userInterfaceSystem.IsUiOpen(ent, PowerMonitoringConsoleUiKey.Key))
                     continue;
 
-                foreach (var session in bui.SubscribedSessions)
+                UpdateUIState(ent, console);
-                    UpdateUIState(ent, console, session);
+
             }
         }
     }
 
-    public void UpdateUIState(EntityUid uid, PowerMonitoringConsoleComponent component, ICommonSession session)
+    private void UpdateUIState(EntityUid uid, PowerMonitoringConsoleComponent component)
     {
-        if (!_userInterfaceSystem.TryGetUi(uid, PowerMonitoringConsoleUiKey.Key, out var bui))
-            return;
-
         var consoleXform = Transform(uid);
 
         if (consoleXform?.GridUid == null)
@@ -422,15 +419,15 @@ internal sealed partial class PowerMonitoringConsoleSystem : SharedPowerMonitori
         }
 
         // Set the UI state
-        _userInterfaceSystem.SetUiState(bui,
+        _userInterfaceSystem.SetUiState(uid,
+            PowerMonitoringConsoleUiKey.Key,
             new PowerMonitoringConsoleBoundInterfaceState
                 (totalSources,
                 totalBatteryUsage,
                 totalLoads,
                 allEntries.ToArray(),
                 sourcesForFocus.ToArray(),
-                loadsForFocus.ToArray()),
+                loadsForFocus.ToArray()));
-            session);
     }
 
     private double GetPrimaryPowerValues(EntityUid uid, PowerMonitoringDeviceComponent device, out double powerSupplied, out double powerUsage, out double batteryUsage)