Version: 256.0.0

* Clean up

* Remove "struct UpdateTreesJob"

* Use #pragma

* Use #if DEBUG

* More #if DEBUG

MSBuild/Robust.Engine.Version.props

@@ -1,4 +1,4 @@
 <Project>
 
-    <!-- This file automatically reset by Tools/version.py -->
+    <!-- This file automatically reset by Tools/version.py -->
 

MSBuild/XamlIL.targets

@@ -71,6 +71,6 @@
     </PropertyGroup>
     <Exec
       Condition="'$(_RobustUseExternalMSBuild)' == 'true'"
-      Command="&quot;$(DOTNET_HOST_PATH)&quot; msbuild /nodereuse:false $(MSBuildProjectFile) /t:CompileRobustXaml /p:_RobustForceInternalMSBuild=true /p:Configuration=$(Configuration) /p:RuntimeIdentifier=$(RuntimeIdentifier) /p:TargetFramework=$(TargetFramework) /p:BuildProjectReferences=false"/>
+      Command="&quot;$(DOTNET_HOST_PATH)&quot; msbuild /nodereuse:false $(MSBuildProjectFile) /t:CompileRobustXaml /p:_RobustForceInternalMSBuild=true /p:Configuration=$(Configuration) /p:RuntimeIdentifier=$(RuntimeIdentifier) /p:TargetFramework=$(TargetFramework) /p:BuildProjectReferences=false /p:IntermediateOutputPath=&quot;$(IntermediateOutputPath.TrimEnd('\'))/&quot;"/>
   </Target>
 </Project>

RELEASE-NOTES.md

@@ -1,4 +1,4 @@
-# Release notes for RobustToolbox.
+# Release notes for RobustToolbox.
 
 <!--
 NOTE: automatically updated sometimes by version.py.
@@ -54,6 +54,139 @@ END TEMPLATE-->
 *None yet*
 
 
+## 256.0.0
+
+### Breaking changes
+
+* `ITypeReaderWriter<TType, TNode>` has been removed due to being unused. Implement `ITypeSerializer<TType, TNode>` instead
+* Moved AsNullable extension methods to the Entity struct.
+
+### New features
+
+* Add DevWindow tab to show all loaded textures.
+* Add Vector2i / bitmask converfsion helpers.
+* Allow texture preload to be skipped for some textures.
+* Check audio file signatures instead of extensions.
+* Add CancellationTokenRegistration to sandbox.
+* Add the ability to serialize TimeSpan from text.
+* Add support for rotated / mirrored tiles.
+
+### Bugfixes
+
+* Fix yaml hot reloading.
+* Fix a linear dictionary lookup in PlacementManager.
+
+### Other
+
+* Make ItemList not run deselection callback on all items if they aren't selected.
+* Cleanup warnings for CS0649 & CS0414.
+
+### Internal
+
+* Move PointLight component states to shared.
+
+
+## 255.1.0
+
+### New features
+
+* The client localisation manager now supports hot-reloading ftl files.
+* TransformSystem can now raise `GridUidChangedEvent` and `MapUidChangedEvent` when a entity's grid or map changes. This event is only raised if the `ExtraTransformEvents` metadata flag is enabled.
+
+### Bugfixes
+
+* Fixed a server crash due to a `NullReferenceException` in PVS system when a player's local entity is also one of their view subscriptions.
+* Fix CompileRobustXamlTask for benchmarks.
+* .ftl files will now hot reload.
+* Fix placementmanager sometimes not clearing.
+
+### Other
+
+* Container events are now documented.
+
+
+## 255.0.0
+
+### Breaking changes
+
+* `RobustIntegrationTest` now pools server/client instances by default. If a custom settings class is provided, it will still disable pooling unless explicitly enabled.
+  * Server/Client instances that are returned to the pool should be disconnected. This might require you to update some tests.
+  * Pooled instances also require you to use `RobustIntegrationTest` methods like `WaitPost()` to ensure the correct thread is used.
+
+### Bugfixes
+
+* Fix `EntityDeserializer` improperly setting entity lifestages when loading a post-mapinit map.
+* Fix `EntityManager.PredictedDeleteEntity()` not deleting pure client-side entities.
+* Fix grid fixtures using a locale dependent id. This could cause some clients to crash/freeze when connected to a server with a different locale.
+
+### Other
+
+* Add logic to block cycles in master MIDI renderers, which could otherwise cause client freezes.
+
+
+## 254.1.0
+
+### New features
+
+* Add CC ND licences to the RGA validator.
+* Add entity spawn prediction and entity deletion prediction. This is currently limited as you are unable to predict interactions with these entities. These are done via the new methods prefixed with "Predicted". You can also manually flag an entity as a predicted spawn with the `FlagPredicted` method which will clean it up when prediction is reset.
+
+### Bugfixes
+
+* Fix tile edge rendering for neighbor tiles being the same priority.
+
+### Other
+
+* Fix SpawnAttachedTo's system proxy method not the rotation arg like EntityManager.
+
+
+## 254.0.0
+
+### Breaking changes
+
+* Yaml mappings/dictionaries now only support string keys instead of generic nodes
+  * Several MappingDataNode method arguments or return values now use strings instead of a DataNode object
+  * The MappingDataNode class has various helper methods that still accept a ValueDataNode, but these methods are marked as obsolete and may be removed in the future.
+  * yaml validators should use `MappingDataNode.GetKeyNode()` when validating mapping keys, so that errors can print node start & end information
+* ValueTuple yaml serialization has changed
+  * Previously they would get serialized into a single mapping with one entry (i.e., `{foo : bar }`)
+  * Now they serialize into a sequence (i.e., `[foo, bar]`)
+  * The ValueTuple serializer will still try to read mappings, but due to the MappingDataNode this may fail if the previously serialized "key" can't be read as a simple string
+
+### New features
+
+* Add cvar to disable tile edges.
+* Add GetContainingContainers method to ContainerSystem to recursively get containers upwards on an entity.
+
+### Internal
+
+* Make component lifecycle methods use generics.
+
+
+## 253.0.0
+
+### New features
+
+* Add a new `SerializationManager.PushComposition()` overload that takes in a single parent instead of an array of parents.
+* `BoundUserInterfaceMessageAttempt` once again gets raised as a broadcast event, in addition to being directed.
+  * This effectively reverts the breaking part of the changes made in v252.0.0
+* Fix CreateDistanceJoint using an int instead of a float for minimum distance.
+
+### Bugfixes
+
+* Fix deferred component removal not setting the component's life stage to `ComponentLifeStage.Stopped` if the component has not yet been initialised.
+* Fix some `EntitySystem.Resolve()` overloads not respecting the optional `logMissing` argument.
+* Fix screen-space overlays not being useable without first initializing/starting entity manager & systems
+* ItemList is now significantly optimized. VV's `AddComponent` window in particular should be much faster.
+* Fix some more MapValidator fields.
+* Fix popup text overflowing the sides of the screen.
+* Improve location reporting for non-writeable datafields via analyzer.
+
+### Other
+
+* TestPoint now uses generics rather than IPhysShape directly.
+
+
 ## 252.0.0
 
 ### Breaking changes

Resources/Locale/en-US/commands.ftl

@@ -1,5 +1,7 @@
 ### Localization for engine console commands
 
+cmd-hint-float = [float]
+
 ## generic command errors
 
 cmd-invalid-arg-number-error = Invalid number of arguments.

Resources/Locale/en-US/custom-controls.ftl

@@ -9,6 +9,7 @@ entity-spawn-window-override-menu-tooltip = Override placement
 ## TileSpawnWindow
 
 tile-spawn-window-title = Place Tiles
+tile-spawn-window-mirror-button-text = Mirror Tiles
 
 ## Console
 

Resources/Locale/en-US/dev-window.ftl

@@ -0,0 +1,10 @@
+## "Textures" dev window tab
+
+dev-window-tab-textures-title = Textures
+dev-window-tab-textures-reload = Reload
+dev-window-tab-textures-filter = Filter
+dev-window-tab-textures-summary = Total (est): { $bytes }
+dev-window-tab-textures-info = Width: { $width } Height: { $height }
+    PixelType: { $pixelType } sRGB: { $srgb }
+    Name: { $name }
+    Est. memory usage: { $bytes }

Robust.Analyzers.Tests/DataDefinitionAnalyzerTest.cs

@@ -87,4 +87,66 @@ public sealed class DataDefinitionAnalyzerTest
             VerifyCS.Diagnostic(DataDefinitionAnalyzer.DataFieldNoVVReadWriteRule).WithSpan(35, 17, 35, 50).WithArguments("Bad", "Foo")
         );
     }
+
+    [Test]
+    public async Task ReadOnlyFieldTest()
+    {
+        const string code = """
+            using System;
+            using Robust.Shared.Serialization.Manager.Attributes;
+
+            namespace Robust.Shared.Serialization.Manager.Attributes
+            {
+                public class DataFieldBaseAttribute : Attribute;
+                public class DataFieldAttribute : DataFieldBaseAttribute;
+                public sealed class DataDefinitionAttribute : Attribute;
+            }
+
+            [DataDefinition]
+            public sealed partial class Foo
+            {
+                [DataField]
+                public readonly int Bad;
+
+                [DataField]
+                public int Good;
+            }
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(15,12): error RA0019: Data field Bad in data definition Foo is readonly
+            VerifyCS.Diagnostic(DataDefinitionAnalyzer.DataFieldWritableRule).WithSpan(15, 12, 15, 20).WithArguments("Bad", "Foo")
+        );
+    }
+
+    [Test]
+    public async Task ReadOnlyPropertyTest()
+    {
+        const string code = """
+            using System;
+            using Robust.Shared.Serialization.Manager.Attributes;
+
+            namespace Robust.Shared.Serialization.Manager.Attributes
+            {
+                public class DataFieldBaseAttribute : Attribute;
+                public class DataFieldAttribute : DataFieldBaseAttribute;
+                public sealed class DataDefinitionAttribute : Attribute;
+            }
+
+            [DataDefinition]
+            public sealed partial class Foo
+            {
+                [DataField]
+                public int Bad { get; }
+
+                [DataField]
+                public int Good { get; private set; }
+            }
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(15,20): error RA0020: Data field property Bad in data definition Foo does not have a setter
+            VerifyCS.Diagnostic(DataDefinitionAnalyzer.DataFieldPropertyWritableRule).WithSpan(15, 20, 15, 28).WithArguments("Bad", "Foo")
+        );
+    }
 }

Robust.Analyzers.Tests/ObsoleteInheritanceAnalyzerTest.cs

@@ -0,0 +1,86 @@
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CSharp.Testing;
+using Microsoft.CodeAnalysis.Testing;
+using NUnit.Framework;
+using VerifyCS =
+    Microsoft.CodeAnalysis.CSharp.Testing.CSharpAnalyzerVerifier<Robust.Analyzers.ObsoleteInheritanceAnalyzer, Microsoft.CodeAnalysis.Testing.DefaultVerifier>;
+
+namespace Robust.Analyzers.Tests;
+
+/// <summary>
+/// Analyzer that implements <c>[ObsoleteInheritance]</c> checking, to give obsoletion warnings for inheriting types
+/// that should never have been virtual.
+/// </summary>
+[Parallelizable(ParallelScope.All | ParallelScope.Fixtures)]
+[TestFixture]
+public sealed class ObsoleteInheritanceAnalyzerTest
+{
+    private static Task Verifier(string code, params DiagnosticResult[] expected)
+    {
+        var test = new CSharpAnalyzerTest<ObsoleteInheritanceAnalyzer, DefaultVerifier>()
+        {
+            TestState =
+            {
+                Sources = { code },
+            },
+        };
+
+        TestHelper.AddEmbeddedSources(
+            test.TestState,
+            "Robust.Shared.Analyzers.ObsoleteInheritanceAttribute.cs"
+        );
+
+        // ExpectedDiagnostics cannot be set, so we need to AddRange here...
+        test.TestState.ExpectedDiagnostics.AddRange(expected);
+
+        return test.RunAsync();
+    }
+
+    [Test]
+    public async Task TestBasic()
+    {
+        const string code = """
+            using Robust.Shared.Analyzers;
+
+            [ObsoleteInheritance]
+            public class Base;
+
+            public class NotAllowed : Base;
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(6,14): warning RA0034: Type 'NotAllowed' inherits from 'Base', which has obsoleted inheriting from itself
+            VerifyCS.Diagnostic(ObsoleteInheritanceAnalyzer.Rule).WithSpan(6, 14, 6, 24).WithArguments("NotAllowed", "Base")
+            );
+    }
+
+    [Test]
+    public async Task TestMessage()
+    {
+        const string code = """
+            using Robust.Shared.Analyzers;
+
+            [ObsoleteInheritance("Sus")]
+            public class Base;
+
+            public class NotAllowed : Base;
+            """;
+
+        await Verifier(code,
+            // /0/Test0.cs(6,14): warning RA0034: Type 'NotAllowed' inherits from 'Base', which has obsoleted inheriting from itself: "Sus"
+            VerifyCS.Diagnostic(ObsoleteInheritanceAnalyzer.RuleWithMessage).WithSpan(6, 14, 6, 24).WithArguments("NotAllowed", "Base", "Sus")
+        );
+    }
+
+    [Test]
+    public async Task TestNormal()
+    {
+        const string code = """
+            public class Base;
+
+            public class AllowedAllowed : Base;
+            """;
+
+        await Verifier(code);
+    }
+}

Robust.Analyzers.Tests/Robust.Analyzers.Tests.csproj

@@ -14,6 +14,7 @@
     <EmbeddedResource Include="..\Robust.Shared\Analyzers\PreferNonGenericVariantForAttribute.cs" LogicalName="Robust.Shared.Analyzers.PreferNonGenericVariantForAttribute.cs" LinkBase="Implementations" />
     <EmbeddedResource Include="..\Robust.Shared\Analyzers\PreferOtherTypeAttribute.cs" LogicalName="Robust.Shared.Analyzers.PreferOtherTypeAttribute.cs" LinkBase="Implementations" />
     <EmbeddedResource Include="..\Robust.Shared\Analyzers\ForbidLiteralAttribute.cs" LogicalName="Robust.Shared.Analyzers.ForbidLiteralAttribute.cs" LinkBase="Implementations" />
+    <EmbeddedResource Include="..\Robust.Shared\Analyzers\ObsoleteInheritanceAttribute.cs" LogicalName="Robust.Shared.Analyzers.ObsoleteInheritanceAttribute.cs" LinkBase="Implementations" />
     <EmbeddedResource Include="..\Robust.Shared\IoC\DependencyAttribute.cs" LogicalName="Robust.Shared.IoC.DependencyAttribute.cs" LinkBase="Implementations" />
     <EmbeddedResource Include="..\Robust.Shared\GameObjects\EventBusAttributes.cs" LogicalName="Robust.Shared.GameObjects.EventBusAttributes.cs" LinkBase="Implementations" />
   </ItemGroup>

Robust.Analyzers/DataDefinitionAnalyzer.cs

@@ -41,7 +41,7 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
         "Make sure to mark any type containing a nested data definition as partial."
     );
 
-    private static readonly DiagnosticDescriptor DataFieldWritableRule = new(
+    public static readonly DiagnosticDescriptor DataFieldWritableRule = new(
         Diagnostics.IdDataFieldWritable,
         "Data field must not be readonly",
         "Data field {0} in data definition {1} is readonly",
@@ -51,7 +51,7 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
         "Make sure to remove the readonly modifier."
     );
 
-    private static readonly DiagnosticDescriptor DataFieldPropertyWritableRule = new(
+    public static readonly DiagnosticDescriptor DataFieldPropertyWritableRule = new(
         Diagnostics.IdDataFieldPropertyWritable,
         "Data field property must have a setter",
         "Data field property {0} in data definition {1} does not have a setter",
@@ -149,7 +149,8 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
 
             if (IsReadOnlyDataField(type, fieldSymbol))
             {
-                context.ReportDiagnostic(Diagnostic.Create(DataFieldWritableRule, context.Node.GetLocation(), fieldSymbol.Name, type.Name));
+                TryGetModifierLocation(field, SyntaxKind.ReadOnlyKeyword, out var location);
+                context.ReportDiagnostic(Diagnostic.Create(DataFieldWritableRule, location, fieldSymbol.Name, type.Name));
             }
 
             if (HasRedundantTag(fieldSymbol))
@@ -185,7 +186,8 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
 
         if (IsReadOnlyDataField(type, propertySymbol))
         {
-            context.ReportDiagnostic(Diagnostic.Create(DataFieldPropertyWritableRule, context.Node.GetLocation(), propertySymbol.Name, type.Name));
+            var location = property.AccessorList != null ? property.AccessorList.GetLocation() : property.GetLocation();
+            context.ReportDiagnostic(Diagnostic.Create(DataFieldPropertyWritableRule, location, propertySymbol.Name, type.Name));
         }
 
         if (HasRedundantTag(propertySymbol))
@@ -285,6 +287,20 @@ public sealed class DataDefinitionAnalyzer : DiagnosticAnalyzer
         return false;
     }
 
+    private static bool TryGetModifierLocation(MemberDeclarationSyntax syntax, SyntaxKind modifierKind, out Location location)
+    {
+        foreach (var modifier in syntax.Modifiers)
+        {
+            if (modifier.IsKind(modifierKind))
+            {
+                location = modifier.GetLocation();
+                return true;
+            }
+        }
+        location = syntax.GetLocation();
+        return false;
+    }
+
     private static bool IsReadOnlyMember(ITypeSymbol type, ISymbol member)
     {
         if (member is IFieldSymbol field)

Robust.Analyzers/ObsoleteInheritanceAnalyzer.cs

@@ -0,0 +1,75 @@
+#nullable enable
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Robust.Roslyn.Shared;
+
+namespace Robust.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class ObsoleteInheritanceAnalyzer : DiagnosticAnalyzer
+{
+    private const string Attribute = "Robust.Shared.Analyzers.ObsoleteInheritanceAttribute";
+
+    public static readonly DiagnosticDescriptor Rule = new(
+        Diagnostics.IdObsoleteInheritance,
+        "Parent type has obsoleted inheritance",
+        "Type '{0}' inherits from '{1}', which has obsoleted inheriting from itself",
+        "Usage",
+        DiagnosticSeverity.Warning,
+        true);
+
+    public static readonly DiagnosticDescriptor RuleWithMessage = new(
+        Diagnostics.IdObsoleteInheritanceWithMessage,
+        "Parent type has obsoleted inheritance",
+        "Type '{0}' inherits from '{1}', which has obsoleted inheriting from itself: \"{2}\"",
+        "Usage",
+        DiagnosticSeverity.Warning,
+        true);
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => [Rule, RuleWithMessage];
+
+    public override void Initialize(AnalysisContext context)
+    {
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+        context.EnableConcurrentExecution();
+        context.RegisterSymbolAction(CheckClass, SymbolKind.NamedType);
+    }
+
+    private static void CheckClass(SymbolAnalysisContext context)
+    {
+        if (context.Symbol is not INamedTypeSymbol typeSymbol)
+            return;
+
+        if (typeSymbol.IsValueType || typeSymbol.BaseType is not { } baseType)
+            return;
+
+        if (!AttributeHelper.HasAttribute(baseType, Attribute, out var data))
+            return;
+
+        var location = context.Symbol.Locations[0];
+
+        if (GetMessageFromAttributeData(data) is { } message)
+        {
+            context.ReportDiagnostic(Diagnostic.Create(
+                RuleWithMessage,
+                location,
+                [typeSymbol.Name, baseType.Name, message]));
+        }
+        else
+        {
+            context.ReportDiagnostic(Diagnostic.Create(
+                Rule,
+                location,
+                [typeSymbol.Name, baseType.Name]));
+        }
+    }
+
+    private static string? GetMessageFromAttributeData(AttributeData data)
+    {
+        if (data.ConstructorArguments is not [var message, ..])
+            return null;
+
+        return message.Value as string;
+    }
+}

Robust.Benchmarks/Transform/RecursiveMoveBenchmark.cs

@@ -42,8 +42,8 @@ public class RecursiveMoveBenchmark : RobustIntegrationTest
     public void GlobalSetup()
     {
         ProgramShared.PathOffset = "../../../../";
-        var server = StartServer();
-        var client = StartClient();
+        var server = StartServer(new() {Pool = false});
+        var client = StartClient(new() {Pool = false});
 
         Task.WhenAll(client.WaitIdleAsync(), server.WaitIdleAsync()).Wait();
 

Robust.Client/Audio/Midi/MidiRenderer.cs

@@ -226,6 +226,9 @@ internal sealed class MidiRenderer : IMidiRenderer
             if (value == _master)
                 return;
 
+            if (CheckMasterCycle(value))
+                throw new InvalidOperationException("Tried to set master to a child of this renderer!");
+
             if (_master is { Disposed: false })
             {
                 try
@@ -729,4 +732,22 @@ internal sealed class MidiRenderer : IMidiRenderer
         _synth?.Dispose();
         _player?.Dispose();
     }
+
+    /// <summary>
+    /// Check that a given renderer is not already a child of this renderer, i.e. it would introduce a cycle if set as master of this renderer.
+    /// </summary>
+    private bool CheckMasterCycle(IMidiRenderer? otherRenderer)
+    {
+        // Doesn't inside drift, cringe.
+
+        while (otherRenderer != null)
+        {
+            if (otherRenderer == this)
+                return true;
+
+            otherRenderer = otherRenderer.Master;
+        }
+
+        return false;
+    }
 }

Robust.Client/ClientIoC.cs

@@ -10,6 +10,7 @@ using Robust.Client.Graphics;
 using Robust.Client.Graphics.Clyde;
 using Robust.Client.HWId;
 using Robust.Client.Input;
+using Robust.Client.Localization;
 using Robust.Client.Map;
 using Robust.Client.Placement;
 using Robust.Client.Player;
@@ -36,6 +37,7 @@ using Robust.Shared.Console;
 using Robust.Shared.ContentPack;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Localization;
 using Robust.Shared.Map;
 using Robust.Shared.Network;
 using Robust.Shared.Physics;
@@ -104,6 +106,8 @@ namespace Robust.Client
             deps.Register<IGamePrototypeLoadManager, GamePrototypeLoadManager>();
             deps.Register<NetworkResourceManager>();
             deps.Register<IReloadManager, ReloadManager>();
+            deps.Register<ILocalizationManager, ClientLocalizationManager>();
+            deps.Register<ILocalizationManagerInternal, ClientLocalizationManager>();
 
             switch (mode)
             {

Robust.Client/Console/Commands/DebugAnchoredCommand.cs

@@ -1,17 +1,19 @@
 #if DEBUG
 using Robust.Client.Debugging;
 using Robust.Shared.Console;
-using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
 
 namespace Robust.Client.Console.Commands
 {
-    public sealed class DebugAnchoredCommand : LocalizedCommands
+    public sealed class DebugAnchoredCommand : LocalizedEntityCommands
     {
+        [Dependency] private readonly DebugAnchoringSystem _system = default!;
+
         public override string Command => "showanchored";
 
         public override void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            EntitySystem.Get<DebugAnchoringSystem>().Enabled ^= true;
+            _system.Enabled ^= true;
         }
     }
 }

Robust.Client/Console/Commands/LightBBCommand.cs

@@ -1,17 +1,19 @@
 #if DEBUG
 using Robust.Client.GameObjects;
 using Robust.Shared.Console;
-using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
 
 namespace Robust.Client.Console.Commands
 {
-    internal sealed class LightDebugCommand : LocalizedCommands
+    internal sealed class LightDebugCommand : LocalizedEntityCommands
     {
+        [Dependency] private readonly DebugLightTreeSystem _system = default!;
+
         public override string Command => "lightbb";
 
         public override void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            EntitySystem.Get<DebugLightTreeSystem>().Enabled ^= true;
+            _system.Enabled ^= true;
         }
     }
 }

Robust.Client/Console/Commands/ShowPlayerVelocityCommand.cs

@@ -1,19 +1,18 @@
 using Robust.Client.GameObjects;
 using Robust.Shared.Console;
-using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 
 namespace Robust.Client.Console.Commands
 {
-    public sealed class ShowPlayerVelocityCommand : LocalizedCommands
+    public sealed class ShowPlayerVelocityCommand : LocalizedEntityCommands
     {
-        [Dependency] private readonly IEntitySystemManager _entitySystems = default!;
+        [Dependency] private readonly ShowPlayerVelocityDebugSystem _system = default!;
 
         public override string Command => "showplayervelocity";
 
         public override void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            _entitySystems.GetEntitySystem<ShowPlayerVelocityDebugSystem>().Enabled ^= true;
+            _system.Enabled ^= true;
         }
     }
 }

Robust.Client/GameController/GameController.cs

@@ -31,6 +31,7 @@ using Robust.Shared.Configuration;
 using Robust.Shared.ContentPack;
 using Robust.Shared.Exceptions;
 using Robust.Shared.IoC;
+using Robust.Shared.Localization;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
 using Robust.Shared.Network;
@@ -94,6 +95,7 @@ namespace Robust.Client
         [Dependency] private readonly IReplayRecordingManagerInternal _replayRecording = default!;
         [Dependency] private readonly IReflectionManager _reflectionManager = default!;
         [Dependency] private readonly IReloadManager _reload = default!;
+        [Dependency] private readonly ILocalizationManager _loc = default!;
 
         private IWebViewManagerHook? _webViewHook;
 
@@ -180,6 +182,7 @@ namespace Robust.Client
             _serializer.Initialize();
             _inputManager.Initialize();
             _console.Initialize();
+            _loc.Initialize();
 
             // Make sure this is done before we try to load prototypes,
             // avoid any possibility of race conditions causing the check to not finish

Robust.Client/GameObjects/ClientEntityManager.Spawn.cs

@@ -0,0 +1,123 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+using Robust.Shared.Containers;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Utility;
+
+namespace Robust.Client.GameObjects;
+
+public sealed partial class ClientEntityManager
+{
+    public override EntityUid PredictedSpawnAttachedTo(string? protoName, EntityCoordinates coordinates, ComponentRegistry? overrides = null, Angle rotation = default)
+    {
+        var ent = SpawnAttachedTo(protoName, coordinates, overrides, rotation);
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public override EntityUid PredictedSpawn(string? protoName = null, ComponentRegistry? overrides = null, bool doMapInit = true)
+    {
+        var ent = Spawn(protoName, overrides, doMapInit);
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    public override EntityUid PredictedSpawn(string? protoName, MapCoordinates coordinates, ComponentRegistry? overrides = null, Angle rotation = default!)
+    {
+        var ent = Spawn(protoName, coordinates, overrides, rotation);
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    public override EntityUid PredictedSpawnAtPosition(string? protoName, EntityCoordinates coordinates, ComponentRegistry? overrides = null)
+    {
+        var ent = SpawnAtPosition(protoName, coordinates, overrides);
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    public override bool PredictedTrySpawnNextTo(
+        string? protoName,
+        EntityUid target,
+        [NotNullWhen(true)] out EntityUid? uid,
+        TransformComponent? xform = null,
+        ComponentRegistry? overrides = null)
+    {
+        if (!TrySpawnNextTo(protoName, target, out uid, xform, overrides))
+            return false;
+
+        FlagPredicted(uid.Value);
+        return true;
+    }
+
+    public override bool PredictedTrySpawnInContainer(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        [NotNullWhen(true)] out EntityUid? uid,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        if (!TrySpawnInContainer(protoName, containerUid, containerId, out uid, containerComp, overrides))
+            return false;
+
+        FlagPredicted(uid.Value);
+        return true;
+    }
+
+    public override EntityUid PredictedSpawnNextToOrDrop(string? protoName, EntityUid target, TransformComponent? xform = null, ComponentRegistry? overrides = null)
+    {
+        var ent = SpawnNextToOrDrop(protoName, target, xform, overrides);
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    public override EntityUid PredictedSpawnInContainerOrDrop(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        TransformComponent? xform = null,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        var ent = SpawnInContainerOrDrop(protoName, containerUid, containerId, xform, containerComp, overrides);
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    public override EntityUid PredictedSpawnInContainerOrDrop(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        out bool inserted,
+        TransformComponent? xform = null,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        var ent = SpawnInContainerOrDrop(protoName,
+            containerUid,
+            containerId,
+            out inserted,
+            xform,
+            containerComp,
+            overrides);
+
+        FlagPredicted(ent);
+        return ent;
+    }
+
+    public override void FlagPredicted(Entity<MetaDataComponent?> ent)
+    {
+        if (!MetaQuery.Resolve(ent.Owner, ref ent.Comp))
+            return;
+
+        DebugTools.Assert(IsClientSide(ent.Owner, ent.Comp));
+        EnsureComponent<PredictedSpawnComponent>(ent.Owner);
+
+        // TODO: Need to map call site or something, needs to be consistent between client and server.
+    }
+}

Robust.Client/GameObjects/ClientEntityManager.cs

@@ -291,5 +291,54 @@ namespace Robust.Client.GameObjects
             }
         }
         #endregion
+
+        /// <inheritdoc />
+        public override void PredictedDeleteEntity(Entity<MetaDataComponent?, TransformComponent?> ent)
+        {
+            if (!MetaQuery.Resolve(ent.Owner, ref ent.Comp1)
+                || ent.Comp1.EntityDeleted
+                || !TransformQuery.Resolve(ent.Owner, ref ent.Comp2))
+            {
+                return;
+            }
+
+            // So there's 3 scenarios:
+            // 1. Networked entity we just move to nullspace and rely on state handling.
+            // 2. Clientside predicted entity we delete and rely on state handling.
+            // 3. Clientside only entity that actually needs deleting here.
+
+            if (ent.Comp1.NetEntity.IsClientSide())
+            {
+                DeleteEntity(ent, ent.Comp1, ent.Comp2);
+            }
+            else
+            {
+                _xforms.DetachEntity(ent, ent.Comp2);
+            }
+        }
+
+        /// <inheritdoc />
+        public override void PredictedQueueDeleteEntity(Entity<MetaDataComponent?, TransformComponent?> ent)
+        {
+            if (IsQueuedForDeletion(ent.Owner)
+                || !MetaQuery.Resolve(ent.Owner, ref ent.Comp1)
+                || ent.Comp1.EntityDeleted
+                || !TransformQuery.Resolve(ent.Owner, ref ent.Comp2))
+            {
+                return;
+            }
+
+            if (ent.Comp1.NetEntity.IsClientSide())
+            {
+                // client-side QueueDeleteEntity re-fetches MetadataComp and checks IsClientSide().
+                // base call to skip that.
+                // TODO create override that takes in metadata comp
+                base.QueueDeleteEntity(ent);
+            }
+            else
+            {
+                _xforms.DetachEntity(ent.Owner, ent.Comp2);
+            }
+        }
     }
 }

Robust.Client/GameObjects/Components/Renderable/SpriteBoundsOverlay.cs

@@ -10,19 +10,21 @@ using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
 {
-    public sealed class ShowSpriteBBCommand : LocalizedCommands
+    public sealed class ShowSpriteBBCommand : LocalizedEntityCommands
     {
+        [Dependency] private readonly SpriteBoundsSystem _system = default!;
+
         public override string Command => "showspritebb";
 
         public override void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            EntitySystem.Get<SpriteBoundsSystem>().Enabled ^= true;
+            _system.Enabled ^= true;
         }
     }
 
     public sealed class SpriteBoundsSystem : EntitySystem
     {
-        [Dependency] private readonly IEntityManager _entityManager = default!;
+        [Dependency] private readonly SharedTransformSystem _xformSystem = default!;
         [Dependency] private readonly IOverlayManager _overlayManager = default!;
         [Dependency] private readonly SpriteTreeSystem _spriteTree = default!;
 
@@ -40,7 +42,7 @@ namespace Robust.Client.GameObjects
                 if (_enabled)
                 {
                     DebugTools.AssertNull(_overlay);
-                    _overlay = new SpriteBoundsOverlay(_spriteTree, _entityManager);
+                    _overlay = new SpriteBoundsOverlay(_spriteTree, _xformSystem);
                     _overlayManager.AddOverlay(_overlay);
                 }
                 else
@@ -59,13 +61,13 @@ namespace Robust.Client.GameObjects
     {
         public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
-        private readonly IEntityManager _entityManager;
+        private readonly SharedTransformSystem _xformSystem;
         private SpriteTreeSystem _renderTree;
 
-        public SpriteBoundsOverlay(SpriteTreeSystem renderTree, IEntityManager entityManager)
+        public SpriteBoundsOverlay(SpriteTreeSystem renderTree, SharedTransformSystem xformSystem)
         {
             _renderTree = renderTree;
-            _entityManager = entityManager;
+            _xformSystem = xformSystem;
         }
 
         protected internal override void Draw(in OverlayDrawArgs args)
@@ -76,7 +78,7 @@ namespace Robust.Client.GameObjects
 
             foreach (var (sprite, xform) in _renderTree.QueryAabb(currentMap, viewport))
             {
-                var (worldPos, worldRot) = xform.GetWorldPositionRotation();
+                var (worldPos, worldRot) = _xformSystem.GetWorldPositionRotation(xform);
                 var bounds = sprite.CalculateRotatedBoundingBox(worldPos, worldRot, args.Viewport.Eye?.Rotation ?? default);
 
                 // Get scaled down bounds used to indicate the "south" of a sprite.

Robust.Client/GameObjects/EntitySystems/AnimationPlayerSystem.cs

@@ -14,7 +14,9 @@ namespace Robust.Client.GameObjects
         private EntityQuery<AnimationPlayerComponent> _playerQuery;
         private EntityQuery<MetaDataComponent> _metaQuery;
 
+#pragma warning disable CS0414
         [Dependency] private readonly IComponentFactory _compFact = default!;
+#pragma warning restore CS0414
 
         public override void Initialize()
         {

Robust.Client/GameObjects/EntitySystems/ContainerSystem.cs

@@ -303,7 +303,7 @@ namespace Robust.Client.GameObjects
             while (parent.IsValid() && (!spriteOccluded || !lightOccluded))
             {
                 var parentXform = TransformQuery.GetComponent(parent);
-                if (TryComp<ContainerManagerComponent>(parent, out var manager) && manager.TryGetContainer(child, out var container))
+                if (TryComp<ContainerManagerComponent>(parent, out var manager) && TryGetContainingContainer(parent, child, out var container, manager))
                 {
                     spriteOccluded = spriteOccluded || !container.ShowContents;
                     lightOccluded = lightOccluded || container.OccludesLight;
@@ -344,7 +344,7 @@ namespace Robust.Client.GameObjects
                     var childLightOccluded = lightOccluded;
 
                     // We already know either sprite or light is not occluding so need to check container.
-                    if (manager.TryGetContainer(child, out var container))
+                    if (TryGetContainingContainer(entity, child, out var container, manager))
                     {
                         childSpriteOccluded = childSpriteOccluded || !container.ShowContents;
                         childLightOccluded = childLightOccluded || container.OccludesLight;

Robust.Client/GameObjects/EntitySystems/DebugEntityLookupSystem.cs

@@ -2,24 +2,24 @@ using System.Collections.Generic;
 using System.Numerics;
 using Robust.Client.Graphics;
 using Robust.Shared.Console;
-using Robust.Shared.Containers;
 using Robust.Shared.Enums;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics.Dynamics;
-using Robust.Shared.Utility;
 using Color = Robust.Shared.Maths.Color;
 
 namespace Robust.Client.GameObjects;
 
-public sealed class DebugEntityLookupCommand : LocalizedCommands
+public sealed class DebugEntityLookupCommand : LocalizedEntityCommands
 {
+    [Dependency] private readonly DebugEntityLookupSystem _system = default!;
+
     public override string Command => "togglelookup";
 
     public override void Execute(IConsoleShell shell, string argStr, string[] args)
     {
-        EntitySystem.Get<DebugEntityLookupSystem>().Enabled ^= true;
+        _system.Enabled ^= true;
     }
 }
 

Robust.Client/GameObjects/EntitySystems/DebugLightTreeSystem.cs

@@ -26,10 +26,10 @@ namespace Robust.Client.GameObjects
                 if (_enabled)
                 {
                     _lightOverlay = new DebugLightOverlay(
-                        EntitySystem.Get<EntityLookupSystem>(),
+                        EntityManager.System<EntityLookupSystem>(),
                         IoCManager.Resolve<IEyeManager>(),
                         IoCManager.Resolve<IMapManager>(),
-                        Get<LightTreeSystem>());
+                        EntityManager.System<LightTreeSystem>());
 
                     overlayManager.AddOverlay(_lightOverlay);
                 }

Robust.Client/GameObjects/EntitySystems/EyeSystem.cs

@@ -62,7 +62,7 @@ public sealed class EyeSystem : SharedEyeSystem
                 eyeComponent.Target = null;
             }
 
-            eyeComponent.Eye.Position = xform.MapPosition;
+            eyeComponent.Eye.Position = TransformSystem.GetMapCoordinates(xform);
         }
     }
 }

Robust.Client/GameObjects/EntitySystems/PointLightSystem.cs

@@ -16,6 +16,7 @@ namespace Robust.Client.GameObjects
         public override void Initialize()
         {
             base.Initialize();
+            SubscribeLocalEvent<PointLightComponent, ComponentGetState>(OnLightGetState);
             SubscribeLocalEvent<PointLightComponent, ComponentInit>(HandleInit);
             SubscribeLocalEvent<PointLightComponent, ComponentHandleState>(OnLightHandleState);
         }

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -13,6 +13,7 @@ using Robust.Client.Physics;
 using Robust.Client.Player;
 using Robust.Client.Timing;
 using Robust.Shared;
+using Robust.Shared.Collections;
 using Robust.Shared.Configuration;
 using Robust.Shared.Console;
 using Robust.Shared.Containers;
@@ -563,6 +564,21 @@ namespace Robust.Client.GameStates
             var metaQuery = _entities.GetEntityQuery<MetaDataComponent>();
             RemQueue<IComponent> toRemove = new();
 
+            // Handle predicted entity spawns.
+            var predicted = new ValueList<EntityUid>();
+            var predictedQuery = _entities.AllEntityQueryEnumerator<PredictedSpawnComponent>();
+
+            while (predictedQuery.MoveNext(out var uid, out var _))
+            {
+                predicted.Add(uid);
+            }
+
+            // Entity will get re-created as part of the tick.
+            foreach (var ent in predicted)
+            {
+                _entities.DeleteEntity(ent);
+            }
+
             foreach (var entity in system.DirtyEntities)
             {
                 DebugTools.Assert(toRemove.Count == 0);

Robust.Client/Graphics/ClientEye/EyeManager.cs

@@ -123,7 +123,8 @@ namespace Robust.Client.Graphics
         /// <inheritdoc />
         public ScreenCoordinates CoordinatesToScreen(EntityCoordinates point)
         {
-            return MapToScreen(point.ToMap(_entityManager, _entityManager.System<SharedTransformSystem>()));
+            var transformSystem = _entityManager.System<SharedTransformSystem>();
+            return MapToScreen(transformSystem.ToMapCoordinates(point));
         }
 
         public ScreenCoordinates MapToScreen(MapCoordinates point)

Robust.Client/Graphics/Clyde/Clyde.GridRendering.cs

@@ -30,6 +30,23 @@ namespace Robust.Client.Graphics.Clyde
         private int _indicesPerChunk(MapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * GetQuadBatchIndexCount();
 
         private List<Entity<MapGridComponent>> _grids = new();
+        private bool _drawTileEdges;
+
+        private void RenderTileEdgesChanges(bool value)
+        {
+            _drawTileEdges = value;
+            if (!value)
+                return;
+
+            // Dirty all Edges
+            foreach (var gridData in _mapChunkData.Values)
+            {
+                foreach (var chunk in gridData.Values)
+                {
+                    chunk.EdgeDirty = true;
+                }
+            }
+        }
 
         private void _drawGrids(Viewport viewport, Box2 worldAABB, Box2Rotated worldBounds, IEye eye)
         {
@@ -81,6 +98,9 @@ namespace Robust.Client.Graphics.Clyde
 
                     _updateChunkMesh(mapGrid, chunk, datum);
 
+                    if (!_drawTileEdges)
+                        continue;
+
                     // Dirty edge tiles for next step.
                     datum.EdgeDirty = true;
 
@@ -99,17 +119,16 @@ namespace Robust.Client.Graphics.Clyde
                     }
                 }
 
-                enumerator = mapSystem.GetMapChunks(mapGrid.Owner, mapGrid.Comp, worldBounds);
-
                 // Handle edge sprites.
-                while (enumerator.MoveNext(out var chunk))
+                if (_drawTileEdges)
                 {
-                    var datum = data[chunk.Indices];
-
-                    if (!datum.EdgeDirty)
-                        continue;
-
-                    _updateChunkEdges(mapGrid, chunk, datum);
+                    enumerator = mapSystem.GetMapChunks(mapGrid.Owner, mapGrid.Comp, worldBounds);
+                    while (enumerator.MoveNext(out var chunk))
+                    {
+                        var datum = data[chunk.Indices];
+                        if (datum.EdgeDirty)
+                            _updateChunkEdges(mapGrid, chunk, datum);
+                    }
                 }
 
                 enumerator = mapSystem.GetMapChunks(mapGrid.Owner, mapGrid.Comp, worldBounds);
@@ -129,7 +148,7 @@ namespace Robust.Client.Graphics.Clyde
                         CheckGlError();
                     }
 
-                    if (datum.EdgeCount > 0)
+                    if (_drawTileEdges && datum.EdgeCount > 0)
                     {
                         BindVertexArray(datum.EdgeVAO);
                         CheckGlError();
@@ -138,7 +157,6 @@ namespace Robust.Client.Graphics.Clyde
                         GL.DrawElements(GetQuadGLPrimitiveType(), datum.EdgeCount * GetQuadBatchIndexCount(), DrawElementsType.UnsignedShort, 0);
                         CheckGlError();
                     }
-
                 }
 
                 requiresFlush = false;
@@ -236,7 +254,11 @@ namespace Robust.Client.Graphics.Clyde
                             region = regionMaybe[tile.Variant];
                         }
 
-                        WriteTileToBuffers(i, gridX, gridY, vertexBuffer, indexBuffer, region);
+                        var rotationMirroring = _tileDefinitionManager[tile.TypeId].AllowRotationMirror
+                            ? tile.RotationMirroring
+                            : 0;
+
+                        WriteTileToBuffers(i, gridX, gridY, vertexBuffer, indexBuffer, region, rotationMirroring);
                         i += 1;
                     }
                 }
@@ -274,7 +296,8 @@ namespace Robust.Client.Graphics.Clyde
                     var gridX = x + chunkOriginScaled.X;
                     var gridY = y + chunkOriginScaled.Y;
                     var tile = chunk.GetTile(x, y);
-                    var tileDef = _tileDefinitionManager[tile.TypeId];
+                    if (!_tileDefinitionManager.TryGetDefinition(tile.TypeId, out var tileDef))
+                        continue;
 
                     // Edge render
                     for (var nx = -1; nx <= 1; nx++)
@@ -288,14 +311,15 @@ namespace Robust.Client.Graphics.Clyde
                             if (!maps.TryGetTile(grid.Comp, neighborIndices, out var neighborTile))
                                 continue;
 
-                            var neighborDef = _tileDefinitionManager[neighborTile.TypeId];
+                            if (!_tileDefinitionManager.TryGetDefinition(neighborTile.TypeId, out var neighborDef))
+                                continue;
 
                             // If it's the same tile then no edge to be drawn.
                             if (tile.TypeId == neighborTile.TypeId || neighborDef.EdgeSprites.Count == 0)
                                 continue;
 
-                            // If neighbor is a lower priority then us then don't draw on our tile.
-                            if (neighborDef.EdgeSpritePriority < tileDef.EdgeSpritePriority)
+                            // If neighbor is a lower or same priority then us then don't draw on our tile.
+                            if (neighborDef.EdgeSpritePriority <= tileDef.EdgeSpritePriority)
                                 continue;
 
                             var direction = new Vector2i(nx, ny).AsDirection().GetOpposite();
@@ -305,7 +329,7 @@ namespace Robust.Client.Graphics.Clyde
                                 continue;
 
                             var region = regionMaybe[0];
-                            WriteTileToBuffers(i, gridX, gridY, vertexBuffer, indexBuffer, region);
+                            WriteTileToBuffers(i, gridX, gridY, vertexBuffer, indexBuffer, region, 0);
                             i += 1;
                         }
                     }
@@ -425,13 +449,57 @@ namespace Robust.Client.Graphics.Clyde
             int gridY,
             Span<Vertex2D> vertexBuffer,
             Span<ushort> indexBuffer,
-            Box2 region)
+            Box2 region,
+            int rotationMirroring)
         {
+            var rLeftBottom = (region.Left, region.Bottom);
+            var rRightBottom = (region.Right, region.Bottom);
+            var rRightTop = (region.Right, region.Top);
+            var rLeftTop = (region.Left, region.Top);
+
+            // The vertices must be changed if there's any rotation or mirroring to the tile
+            if (rotationMirroring != 0)
+            {
+                // Rotate the tile
+                for (int r = 0; r < rotationMirroring % 4; r++)
+                {
+                    (rLeftBottom, rRightBottom, rRightTop, rLeftTop) =
+                        (rLeftTop, rLeftBottom, rRightBottom, rRightTop);
+                }
+
+                // Mirror on the x-axis
+                if (rotationMirroring >= 4)
+                {
+                    if (rotationMirroring % 2 == 0)
+                    {
+                        rLeftBottom = (rLeftBottom.Item1.Equals(region.Left) ? region.Right : region.Left,
+                            rLeftBottom.Item2);
+                        rRightBottom = (rRightBottom.Item1.Equals(region.Left) ? region.Right : region.Left,
+                            rRightBottom.Item2);
+                        rRightTop = (rRightTop.Item1.Equals(region.Left) ? region.Right : region.Left,
+                            rRightTop.Item2);
+                        rLeftTop = (rLeftTop.Item1.Equals(region.Left) ? region.Right : region.Left,
+                            rLeftTop.Item2);
+                    }
+                    else
+                    {
+                        rLeftBottom = (rLeftBottom.Item1,
+                            rLeftBottom.Item2.Equals(region.Bottom) ? region.Top : region.Bottom);
+                        rRightBottom = (rRightBottom.Item1,
+                            rRightBottom.Item2.Equals(region.Bottom) ? region.Top : region.Bottom);
+                        rRightTop = (rRightTop.Item1,
+                            rRightTop.Item2.Equals(region.Bottom) ? region.Top : region.Bottom);
+                        rLeftTop = (rLeftTop.Item1,
+                            rLeftTop.Item2.Equals(region.Bottom) ? region.Top : region.Bottom);
+                    }
+                }
+            }
+
             var vIdx = i * 4;
-            vertexBuffer[vIdx + 0] = new Vertex2D(gridX, gridY, region.Left, region.Bottom, Color.White);
-            vertexBuffer[vIdx + 1] = new Vertex2D(gridX + 1, gridY, region.Right, region.Bottom, Color.White);
-            vertexBuffer[vIdx + 2] = new Vertex2D(gridX + 1, gridY + 1, region.Right, region.Top, Color.White);
-            vertexBuffer[vIdx + 3] = new Vertex2D(gridX, gridY + 1, region.Left, region.Top, Color.White);
+            vertexBuffer[vIdx + 0] = new Vertex2D(gridX, gridY, rLeftBottom.Left, rLeftBottom.Bottom, Color.White);
+            vertexBuffer[vIdx + 1] = new Vertex2D(gridX + 1, gridY, rRightBottom.Right, rRightBottom.Bottom, Color.White);
+            vertexBuffer[vIdx + 2] = new Vertex2D(gridX + 1, gridY + 1, rRightTop.Right, rRightTop.Top, Color.White);
+            vertexBuffer[vIdx + 3] = new Vertex2D(gridX, gridY + 1, rLeftTop.Left, rLeftTop.Top, Color.White);
             var nIdx = i * GetQuadBatchIndexCount();
             var tIdx = (ushort)(i * 4);
             QuadBatchIndexWrite(indexBuffer, ref nIdx, tIdx);

Robust.Client/Graphics/Clyde/Clyde.HLR.cs

@@ -123,9 +123,13 @@ namespace Robust.Client.Graphics.Clyde
 
         private void RenderSingleWorldOverlay(Overlay overlay, Viewport vp, OverlaySpace space, in Box2 worldBox, in Box2Rotated worldBounds)
         {
+            // Check that entity manager has started.
+            // This is required for us to be able to use MapSystem.
+            DebugTools.Assert(_entityManager.Started, "Entity manager should be started/initialized before rendering world-space overlays");
+
             DebugTools.Assert(space != OverlaySpace.ScreenSpaceBelowWorld && space != OverlaySpace.ScreenSpace);
 
-            var mapId = vp.Eye!.Position.MapId;
+            var mapId = vp.Eye?.Position.MapId ?? MapId.Nullspace;
             var args = new OverlayDrawArgs(space, null, vp, _renderHandle, new UIBox2i((0, 0), vp.Size), _mapSystem.GetMapOrInvalid(mapId), mapId, worldBox, worldBounds);
 
             if (!overlay.BeforeDraw(args))
@@ -152,6 +156,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private void RenderOverlays(Viewport vp, OverlaySpace space, in Box2 worldBox, in Box2Rotated worldBounds)
         {
+            DebugTools.Assert(space != OverlaySpace.ScreenSpaceBelowWorld && space != OverlaySpace.ScreenSpace);
             using (DebugGroup($"Overlays: {space}"))
             {
                 foreach (var overlay in GetOverlaysForSpace(space))
@@ -176,9 +181,18 @@ namespace Robust.Client.Graphics.Clyde
 
             var worldBounds = CalcWorldBounds(vp);
             var worldAABB = worldBounds.CalcBoundingBox();
-            var mapId = vp.Eye!.Position.MapId;
+            var mapId = vp.Eye?.Position.MapId ?? MapId.Nullspace;
+            var mapUid = EntityUid.Invalid;
 
-            var args = new OverlayDrawArgs(space, vpControl, vp, handle, bounds, _mapSystem.GetMapOrInvalid(mapId), mapId, worldAABB, worldBounds);
+            // Screen space overlays may be getting used before entity manager & entity systems have been initialized.
+            // This might mean that _mapSystem is currently null.
+            // ReSharper disable once ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract
+            if (_entityManager.Started && _mapSystem != null)
+                mapUid = _mapSystem.GetMapOrInvalid(mapId);
+
+            DebugTools.Assert(_mapSystem != null || !_entityManager.Started);
+
+            var args = new OverlayDrawArgs(space, vpControl, vp, handle, bounds, mapUid, mapId, worldAABB, worldBounds);
 
             foreach (var overlay in list)
             {

Robust.Client/Graphics/Clyde/Clyde.Textures.cs

@@ -305,8 +305,8 @@ namespace Robust.Client.Graphics.Clyde
                 IsSrgb = srgb,
                 Name = name,
                 MemoryPressure = memoryPressure,
-                TexturePixelType = pixType
-                // TextureInstance = new WeakReference<ClydeTexture>(instance)
+                TexturePixelType = pixType,
+                TextureInstance = new WeakReference<ClydeTexture>(instance)
             };
 
             _loadedTextures.Add(id, loaded);
@@ -466,15 +466,15 @@ namespace Robust.Client.Graphics.Clyde
         {
             var white = new Image<Rgba32>(1, 1);
             white[0, 0] = new Rgba32(255, 255, 255, 255);
-            _stockTextureWhite = (ClydeTexture) Texture.LoadFromImage(white);
+            _stockTextureWhite = (ClydeTexture) Texture.LoadFromImage(white, name: "StockTextureWhite");
 
             var black = new Image<Rgba32>(1, 1);
             black[0, 0] = new Rgba32(0, 0, 0, 255);
-            _stockTextureBlack = (ClydeTexture) Texture.LoadFromImage(black);
+            _stockTextureBlack = (ClydeTexture) Texture.LoadFromImage(black, name: "StockTextureBlack");
 
             var blank = new Image<Rgba32>(1, 1);
             blank[0, 0] = new Rgba32(0, 0, 0, 0);
-            _stockTextureTransparent = (ClydeTexture) Texture.LoadFromImage(blank);
+            _stockTextureTransparent = (ClydeTexture) Texture.LoadFromImage(blank, name: "StockTextureTransparent");
         }
 
         /// <summary>
@@ -571,7 +571,7 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        private sealed class LoadedTexture
+        internal sealed class LoadedTexture
         {
             public GLHandle OpenGLObject;
             public int Width;
@@ -582,10 +582,10 @@ namespace Robust.Client.Graphics.Clyde
             public TexturePixelType TexturePixelType;
 
             public Vector2i Size => (Width, Height);
-            // public WeakReference<ClydeTexture> TextureInstance;
+            public required WeakReference<ClydeTexture> TextureInstance;
         }
 
-        private enum TexturePixelType : byte
+        internal enum TexturePixelType : byte
         {
             RenderTarget = 0,
             Rgba32,
@@ -686,5 +686,16 @@ namespace Robust.Client.Graphics.Clyde
                 _ => throw new ArgumentException(nameof(stockTexture))
             };
         }
+
+        public IEnumerable<(ClydeTexture, LoadedTexture)> GetLoadedTextures()
+        {
+            foreach (var loaded in _loadedTextures.Values)
+            {
+                if (!loaded.TextureInstance.TryGetTarget(out var textureInstance))
+                    continue;
+
+                yield return (textureInstance, loaded);
+            }
+        }
     }
 }

Robust.Client/Graphics/Clyde/Clyde.cs

@@ -121,6 +121,7 @@ namespace Robust.Client.Graphics.Clyde
             _cfg.OnValueChanged(CVars.LightSoftShadows, SoftShadowsChanged, true);
             _cfg.OnValueChanged(CVars.MaxLightCount, MaxLightsChanged, true);
             _cfg.OnValueChanged(CVars.MaxOccluderCount, MaxOccludersChanged, true);
+            _cfg.OnValueChanged(CVars.RenderTileEdges, RenderTileEdgesChanges, true);
             // I can't be bothered to tear down and set these threads up in a cvar change handler.
 
             // Windows and Linux can be trusted to not explode with threaded windowing,

Robust.Client/Graphics/Clyde/ClydeHeadless.cs

@@ -72,6 +72,11 @@ namespace Robust.Client.Graphics.Clyde
             return new DummyTexture((1, 1));
         }
 
+        public IEnumerable<(Clyde.ClydeTexture, Clyde.LoadedTexture)> GetLoadedTextures()
+        {
+            return [];
+        }
+
         public ClydeDebugLayers DebugLayers { get; set; }
 
         public string GetKeyName(Keyboard.Key key) => string.Empty;

Robust.Client/Graphics/Clyde/GLObjects/Clyde.GLHandle.cs

@@ -11,7 +11,7 @@ namespace Robust.Client.Graphics.Clyde
         ///     Basically just a handle around the integer object handles returned by OpenGL.
         /// </summary>
         [PublicAPI]
-        private struct GLHandle : IEquatable<GLHandle>
+        internal struct GLHandle : IEquatable<GLHandle>
         {
             public readonly uint Handle;
 

Robust.Client/Graphics/Clyde/Windowing/Glfw.Cursors.cs

@@ -87,11 +87,13 @@ namespace Robust.Client.Graphics.Clyde
                 if (cmd.Cursor != default)
                     ptr = _winThreadCursors[cmd.Cursor].Ptr;
 
+#if DEBUG
                 if (_win32Experience)
                 {
                     // Based on a true story.
                     Thread.Sleep(15);
                 }
+#endif
 
                 GLFW.SetCursor(window, ptr);
             }

Robust.Client/Graphics/Clyde/Windowing/Glfw.cs

@@ -23,7 +23,9 @@ namespace Robust.Client.Graphics.Clyde
             private readonly ISawmill _sawmillGlfw;
 
             private bool _glfwInitialized;
+#if DEBUG
             private bool _win32Experience;
+#endif
 
             public GlfwWindowingImpl(Clyde clyde, IDependencyCollection deps)
             {

Robust.Client/Graphics/IClydeInternal.cs

@@ -54,6 +54,7 @@ namespace Robust.Client.Graphics
         IClydeDebugStats DebugStats { get; }
 
         Texture GetStockTexture(ClydeStockTexture stockTexture);
+        IEnumerable<(Clyde.Clyde.ClydeTexture, Clyde.Clyde.LoadedTexture)> GetLoadedTextures();
 
         ClydeDebugLayers DebugLayers { get; set; }
 

Robust.Client/Input/InputManager.cs

@@ -48,6 +48,7 @@ namespace Robust.Client.Input
         [Dependency] private readonly IUserInterfaceManagerInternal _uiMgr = default!;
         [Dependency] private readonly IConsoleHost _console = default!;
         [Dependency] private readonly ISerializationManager _serialization = default!;
+        private ISawmill _logger = default!;
 
         private bool _currentlyFindingViewport;
 
@@ -114,6 +115,8 @@ namespace Robust.Client.Input
         /// <inheritdoc />
         public void Initialize()
         {
+            _logger = Logger.GetSawmill("input");
+
             NetworkBindMap = new BoundKeyMap(_reflectionManager);
             NetworkBindMap.PopulateKeyFunctionsMap();
 
@@ -130,7 +133,7 @@ namespace Robust.Client.Input
                 }
                 catch (Exception e)
                 {
-                    Logger.ErrorS("input", "Failed to load user keybindings: " + e);
+                    _logger.Error("Failed to load user keybindings: " + e);
                 }
             }
 
@@ -531,8 +534,7 @@ namespace Robust.Client.Input
 
                     if (reg.Type != KeyBindingType.Command && !NetworkBindMap.FunctionExists(reg.Function.FunctionName))
                     {
-                        Logger.DebugS("input", "Key function in {0} does not exist: '{1}'.", file,
-                            reg.Function);
+                        _logger.Debug("Key function in {0} does not exist: '{1}'.", file, reg.Function);
                         invalid = true;
                     }
 

Robust.Client/Localization/ClientLocalizationManager.cs

@@ -0,0 +1,33 @@
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+using Robust.Shared.Utility;
+
+namespace Robust.Client.Localization;
+
+internal sealed class ClientLocalizationManager : LocalizationManager, ILocalizationManagerInternal
+{
+    [Dependency] private readonly IReloadManager _reload = default!;
+
+    void ILocalizationManager.Initialize() => Initialize();
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        _reload.Register(LocaleDirPath, "*.ftl");
+
+        _reload.OnChanged += OnReload;
+    }
+
+    /// <summary>
+    /// Handles Fluent hot reloading via LocalizationManager.ReloadLocalizations()
+    /// </summary>
+    private void OnReload(ResPath args)
+    {
+        if (args.Extension != "ftl")
+            return;
+
+        ReloadLocalizations();
+    }
+}

Robust.Client/Placement/IPlacementManager.cs

@@ -24,10 +24,20 @@ namespace Robust.Client.Placement
         Direction Direction { get; set; }
 
         /// <summary>
-        /// Gets called when Direction changed (presently for EntitySpawnWindow UI)
+        /// Whether a tile placement should be mirrored or not.
+        /// </summary>
+        bool Mirrored { get; set; }
+
+        /// <summary>
+        /// Gets called when Direction changed (presently for EntitySpawnWindow/TileSpawnWindow UI)
         /// </summary>
         event EventHandler DirectionChanged;
 
+        /// <summary>
+        /// Gets called when Mirrored changed (presently for TileSpawnWindow UI)
+        /// </summary>
+        event EventHandler MirroredChanged;
+
         /// <summary>
         /// Gets called when the PlacementManager changed its build/erase mode or when the hijacks changed
         /// </summary>

Robust.Client/Placement/Modes/AlignSimilar.cs

@@ -30,11 +30,13 @@ namespace Robust.Client.Placement.Modes
                 return;
             }
 
-            var mapId = MouseCoords.GetMapId(pManager.EntityManager);
+            var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
+            var mapId = transformSys.GetMapId(MouseCoords);
 
-            var snapToEntities = EntitySystem.Get<EntityLookupSystem>().GetEntitiesInRange(MouseCoords, SnapToRange)
+            var snapToEntities = pManager.EntityManager.System<EntityLookupSystem>()
+                .GetEntitiesInRange(MouseCoords, SnapToRange)
                 .Where(entity => pManager.EntityManager.GetComponent<MetaDataComponent>(entity).EntityPrototype == pManager.CurrentPrototype && pManager.EntityManager.GetComponent<TransformComponent>(entity).MapID == mapId)
-                .OrderBy(entity => (pManager.EntityManager.GetComponent<TransformComponent>(entity).WorldPosition - MouseCoords.ToMapPos(pManager.EntityManager, pManager.EntityManager.System<SharedTransformSystem>())).LengthSquared())
+                .OrderBy(entity => (transformSys.GetWorldPosition(entity) - transformSys.ToMapCoordinates(MouseCoords).Position).LengthSquared())
                 .ToList();
 
             if (snapToEntities.Count == 0)
@@ -51,10 +53,11 @@ namespace Robust.Client.Placement.Modes
 
             var closestBounds = component.BaseRSI.Size;
 
+            var closestPos = transformSys.GetWorldPosition(closestTransform);
             var closestRect =
                 Box2.FromDimensions(
-                    closestTransform.WorldPosition.X - closestBounds.X / 2f,
-                    closestTransform.WorldPosition.Y - closestBounds.Y / 2f,
+                    closestPos.X - closestBounds.X / 2f,
+                    closestPos.Y - closestBounds.Y / 2f,
                     closestBounds.X, closestBounds.Y);
 
             var sides = new[]

Robust.Client/Placement/Modes/AlignSnapgridBorder.cs

@@ -21,7 +21,8 @@ namespace Robust.Client.Placement.Modes
         {
             MouseCoords = ScreenToCursorGrid(mouseScreen);
 
-            var gridIdOpt = MouseCoords.GetGridUid(pManager.EntityManager);
+            var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
+            var gridIdOpt = transformSys.GetGrid(MouseCoords);
             SnapSize = 1f;
             if (gridIdOpt is EntityUid gridId && gridId.IsValid())
             {

Robust.Client/Placement/Modes/AlignTileDense.cs

@@ -16,8 +16,10 @@ namespace Robust.Client.Placement.Modes
         {
             MouseCoords = ScreenToCursorGrid(mouseScreen);
 
+            var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
+
             var tileSize = 1f;
-            var gridIdOpt = MouseCoords.GetGridUid(pManager.EntityManager);
+            var gridIdOpt = transformSys.GetGrid(MouseCoords);
 
             if (gridIdOpt is EntityUid gridId && gridId.IsValid())
             {

Robust.Client/Placement/Modes/AlignTileNonDense.cs

@@ -16,9 +16,11 @@ namespace Robust.Client.Placement.Modes
         {
             MouseCoords = ScreenToCursorGrid(mouseScreen);
 
+            var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
+
             var tileSize = 1f;
 
-            var gridIdOpt = MouseCoords.GetGridUid(pManager.EntityManager);
+            var gridIdOpt = transformSys.GetGrid(MouseCoords);
             if (gridIdOpt is EntityUid gridId && gridId.IsValid())
             {
                 var mapGrid = pManager.EntityManager.GetComponent<MapGridComponent>(gridId);

Robust.Client/Placement/PlacementManager.cs

@@ -174,6 +174,18 @@ namespace Robust.Client.Placement
 
         private Direction _direction = Direction.South;
 
+        private bool _mirrored;
+
+        public bool Mirrored
+        {
+            get => _mirrored;
+            set
+            {
+                _mirrored = value;
+                MirroredChanged?.Invoke(this, EventArgs.Empty);
+            }
+        }
+
         /// <inheritdoc />
         public Direction Direction
         {
@@ -188,6 +200,9 @@ namespace Robust.Client.Placement
         /// <inheritdoc />
         public event EventHandler? DirectionChanged;
 
+        /// <inheritdoc />
+        public event EventHandler? MirroredChanged;
+
         private PlacementOverlay _drawOverlay = default!;
         private bool _isActive;
 
@@ -356,6 +371,12 @@ namespace Robust.Client.Placement
         public event EventHandler? PlacementChanged;
 
         public void Clear()
+        {
+            ClearWithoutDeactivation();
+            IsActive = false;
+        }
+
+        private void ClearWithoutDeactivation()
         {
             PlacementChanged?.Invoke(this, EventArgs.Empty);
             Hijack = null;
@@ -365,7 +386,6 @@ namespace Robust.Client.Placement
             CurrentMode = null;
             DeactivateSpecialPlacement();
             _placenextframe = false;
-            IsActive = false;
             Eraser = false;
             EraserRect = null;
             PlacementOffset = Vector2i.Zero;
@@ -480,18 +500,17 @@ namespace Robust.Client.Placement
 
         public void BeginHijackedPlacing(PlacementInformation info, PlacementHijack? hijack = null)
         {
-            Clear();
+            ClearWithoutDeactivation();
 
-            CurrentPermission = info;
-
-            if (!_modeDictionary.TryFirstOrNull(pair => pair.Key.Equals(CurrentPermission.PlacementOption), out KeyValuePair<string, Type>? placeMode))
+            if (info.PlacementOption is not { } option || !_modeDictionary.TryGetValue(option, out var placeMode))
             {
-                _sawmill.Log(LogLevel.Warning, $"Invalid placement mode `{CurrentPermission.PlacementOption}`");
+                _sawmill.Log(LogLevel.Warning, $"Invalid placement mode `{info.PlacementOption}`");
                 Clear();
                 return;
             }
 
-            CurrentMode = (PlacementMode) Activator.CreateInstance(placeMode.Value.Value, this)!;
+            CurrentPermission = info;
+            CurrentMode = (PlacementMode) Activator.CreateInstance(placeMode, this)!;
 
             if (hijack != null)
             {
@@ -772,7 +791,9 @@ namespace Robust.Client.Placement
                     var grid = EntityManager.GetComponent<MapGridComponent>(gridId);
 
                     // no point changing the tile to the same thing.
-                    if (Maps.GetTileRef(gridId, grid, coordinates).Tile.TypeId == CurrentPermission.TileType)
+                    var tileRef = Maps.GetTileRef(gridId, grid, coordinates).Tile;
+                    if (tileRef.TypeId == CurrentPermission.TileType &&
+                        tileRef.RotationMirroring == Tile.DirectionToByte(Direction) + (Mirrored ? 4 : 0))
                         return;
                 }
 
@@ -796,9 +817,14 @@ namespace Robust.Client.Placement
             };
 
             if (CurrentPermission.IsTile)
+            {
                 message.TileType = CurrentPermission.TileType;
+                message.Mirrored = Mirrored;
+            }
             else
+            {
                 message.EntityTemplateName = CurrentPermission.EntityType;
+            }
 
             // world x and y
             message.NetCoordinates = EntityManager.GetNetCoordinates(coordinates);

Robust.Client/Placement/PlacementMode.cs

@@ -121,8 +121,8 @@ namespace Robust.Client.Placement
             {
                 if (!coordinate.IsValid(pManager.EntityManager))
                     return; // Just some paranoia just in case
-                var worldPos = coordinate.ToMapPos(pManager.EntityManager, transformSys);
-                var worldRot = pManager.EntityManager.GetComponent<TransformComponent>(coordinate.EntityId).WorldRotation + dirAng;
+                var worldPos = transformSys.ToMapCoordinates(coordinate).Position;
+                var worldRot = transformSys.GetWorldRotation(coordinate.EntityId) + dirAng;
 
                 sprite.Color = IsValidPosition(coordinate) ? ValidPlaceColor : InvalidPlaceColor;
                 var rot = args.Viewport.Eye?.Rotation ?? default;
@@ -230,7 +230,7 @@ namespace Robust.Client.Placement
 
             var range = pManager.CurrentPermission!.Range;
             var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
-            if (range > 0 && !pManager.EntityManager.GetComponent<TransformComponent>(controlled).Coordinates.InRange(pManager.EntityManager, transformSys, coordinates, range))
+            if (range > 0 && !transformSys.InRange(pManager.EntityManager.GetComponent<TransformComponent>(controlled).Coordinates, coordinates, range))
                 return false;
             return true;
         }
@@ -239,7 +239,7 @@ namespace Robust.Client.Placement
         {
             var bounds = pManager.ColliderAABB;
             var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
-            var mapCoords = coordinates.ToMap(pManager.EntityManager, transformSys);
+            var mapCoords = transformSys.ToMapCoordinates(coordinates);
             var (x, y) = mapCoords.Position;
 
             var collisionBox = Box2.FromDimensions(
@@ -248,7 +248,9 @@ namespace Robust.Client.Placement
                 bounds.Width,
                 bounds.Height);
 
-            return EntitySystem.Get<SharedPhysicsSystem>().TryCollideRect(collisionBox, mapCoords.MapId);
+            return pManager.EntityManager
+                .System<SharedPhysicsSystem>()
+                .TryCollideRect(collisionBox, mapCoords.MapId);
         }
 
         protected Vector2 ScreenToWorld(Vector2 point)
@@ -265,10 +267,8 @@ namespace Robust.Client.Placement
         {
             var mapCoords = pManager.EyeManager.PixelToMap(coords.Position);
             var transformSys = pManager.EntityManager.System<SharedTransformSystem>();
-
-            if (!pManager.MapManager.TryFindGridAt(mapCoords, out var gridUid, out var grid))
+            if (!pManager.MapManager.TryFindGridAt(mapCoords, out var gridUid, out _))
             {
-
                 return transformSys.ToCoordinates(mapCoords);
             }
 

Robust.Client/Prototypes/ClientPrototypeManager.cs

@@ -2,9 +2,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using Robust.Client.Timing;
-using Robust.Client.Utility;
 using Robust.Shared.IoC;
-using Robust.Shared.Log;
 using Robust.Shared.Network;
 using Robust.Shared.Network.Messages;
 using Robust.Shared.Prototypes;
@@ -15,7 +13,9 @@ namespace Robust.Client.Prototypes
     public sealed class ClientPrototypeManager : PrototypeManager
     {
         [Dependency] private readonly INetManager _netManager = default!;
+#pragma warning disable CS0414
         [Dependency] private readonly IClientGameTiming _timing = default!;
+#pragma warning restore CS0414
         [Dependency] private readonly IGameControllerInternal _controller = default!;
         [Dependency] private readonly IReloadManager _reload = default!;
 
@@ -56,7 +56,7 @@ namespace Robust.Client.Prototypes
             using var _ = _timing.StartStateApplicationArea();
             ReloadPrototypes([file]);
 
-            Logger.Info($"Reloaded prototypes in {sw.ElapsedMilliseconds} ms");
+            Sawmill.Info($"Reloaded prototypes in {sw.ElapsedMilliseconds} ms");
 #endif
         }
     }

Robust.Client/ResourceManagement/ResourceCache.Preload.cs

@@ -59,7 +59,14 @@ namespace Robust.Client.ResourceManagement
             {
                 try
                 {
-                    TextureResource.LoadPreTexture(_manager, data);
+                    TextureResource.LoadTextureParameters(_manager, data);
+                    if (!data.LoadParameters.Preload)
+                    {
+                        data.Skip = true;
+                        return;
+                    }
+
+                    TextureResource.LoadPreTextureData(_manager, data);
                 }
                 catch (Exception e)
                 {
@@ -72,7 +79,7 @@ namespace Robust.Client.ResourceManagement
 
             foreach (var data in texList)
             {
-                if (data.Bad)
+                if (data.Bad || data.Skip)
                     continue;
 
                 try
@@ -87,6 +94,7 @@ namespace Robust.Client.ResourceManagement
             }
 
             var errors = 0;
+            var skipped = 0;
             foreach (var data in texList)
             {
                 if (data.Bad)
@@ -95,6 +103,12 @@ namespace Robust.Client.ResourceManagement
                     continue;
                 }
 
+                if (data.Skip)
+                {
+                    skipped += 1;
+                    continue;
+                }
+
                 try
                 {
                     var texResource = new TextureResource();
@@ -110,9 +124,10 @@ namespace Robust.Client.ResourceManagement
             }
 
             sawmill.Debug(
-                "Preloaded {CountLoaded} textures ({CountErrored} errored) in {LoadTime}",
-                texList.Length,
+                "Preloaded {CountLoaded} textures ({CountErrored} errored, {CountSkipped} skipped) in {LoadTime}",
+                texList.Length - skipped - errors,
                 errors,
+                skipped,
                 sw.Elapsed);
         }
 

Robust.Client/ResourceManagement/ResourceTypes/AudioResource.cs

@@ -1,8 +1,8 @@
 using System;
 using System.IO;
+using System.Linq;
 using System.Threading;
 using Robust.Client.Audio;
-using Robust.Shared.Audio;
 using Robust.Shared.ContentPack;
 using Robust.Shared.IoC;
 using Robust.Shared.Utility;
@@ -11,6 +11,13 @@ namespace Robust.Client.ResourceManagement;
 
 public sealed class AudioResource : BaseResource
 {
+    // from: https://en.wikipedia.org/wiki/List_of_file_signatures
+    private static readonly byte[] OggSignature = "OggS"u8.ToArray();
+    private static readonly byte[] RiffSignature = "RIFF"u8.ToArray();
+    private const int WavSignatureStart = 8; // RIFF????
+    private static readonly byte[] WavSignature = "WAVE"u8.ToArray();
+    private const int MaxSignatureLength = 12; // RIFF????WAVE
+
     public AudioStream AudioStream { get; private set; } = default!;
 
     public void Load(AudioStream stream)
@@ -28,14 +35,19 @@ public sealed class AudioResource : BaseResource
         }
 
         using var fileStream = cache.ContentFileRead(path);
+        var seekableStream = fileStream.CanSeek ? fileStream : fileStream.CopyToMemoryStream();
+        byte[] signature = seekableStream.ReadExact(MaxSignatureLength);
+        seekableStream.Seek(0, SeekOrigin.Begin);
+
         var audioManager = dependencies.Resolve<IAudioInternal>();
-        if (path.Extension == "ogg")
+        if (signature[..OggSignature.Length].SequenceEqual(OggSignature))
         {
-            AudioStream = audioManager.LoadAudioOggVorbis(fileStream, path.ToString());
+            AudioStream = audioManager.LoadAudioOggVorbis(seekableStream, path.ToString());
         }
-        else if (path.Extension == "wav")
+        else if (signature[..RiffSignature.Length].SequenceEqual(RiffSignature)
+                 && signature[WavSignatureStart..MaxSignatureLength].SequenceEqual(WavSignature))
         {
-            AudioStream = audioManager.LoadAudioWav(fileStream, path.ToString());
+            AudioStream = audioManager.LoadAudioWav(seekableStream, path.ToString());
         }
         else
         {

Robust.Client/ResourceManagement/ResourceTypes/TextureResource.cs

@@ -32,18 +32,22 @@ namespace Robust.Client.ResourceManagement
 
             var data = new LoadStepData {Path = path};
 
-            LoadPreTexture(dependencies.Resolve<IResourceManager>(), data);
+            LoadTextureParameters(dependencies.Resolve<IResourceManager>(), data);
+            LoadPreTextureData(dependencies.Resolve<IResourceManager>(), data);
             LoadTexture(dependencies.Resolve<IClyde>(), data);
             LoadFinish(dependencies.Resolve<IResourceCache>(), data);
         }
 
-        internal static void LoadPreTexture(IResourceManager cache, LoadStepData data)
+        internal static void LoadPreTextureData(IResourceManager cache, LoadStepData data)
         {
             using (var stream = cache.ContentFileRead(data.Path))
             {
                 data.Image = Image.Load<Rgba32>(stream);
             }
+        }
 
+        internal static void LoadTextureParameters(IResourceManager cache, LoadStepData data)
+        {
             data.LoadParameters = TryLoadTextureParameters(cache, data.Path) ?? TextureLoadParameters.Default;
         }
 
@@ -95,7 +99,8 @@ namespace Robust.Client.ResourceManagement
         {
             var data = new LoadStepData {Path = path};
 
-            LoadPreTexture(dependencies.Resolve<IResourceManager>(), data);
+            LoadTextureParameters(dependencies.Resolve<IResourceManager>(), data);
+            LoadPreTextureData(dependencies.Resolve<IResourceManager>(), data);
 
             if (data.Image.Width == Texture.Width && data.Image.Height == Texture.Height)
             {
@@ -119,6 +124,7 @@ namespace Robust.Client.ResourceManagement
             public Image<Rgba32> Image = default!;
             public TextureLoadParameters LoadParameters;
             public OwnedTexture Texture = default!;
+            public bool Skip;
             public bool Bad;
         }
 

Robust.Client/UserInterface/Controllers/Implementations/TileSpawningUIController.cs

@@ -1,8 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using Robust.Client.Graphics;
 using Robust.Client.Placement;
+using Robust.Client.Placement.Modes;
 using Robust.Client.ResourceManagement;
 using Robust.Client.UserInterface.Controls;
 using Robust.Client.UserInterface.CustomControls;
@@ -28,19 +30,23 @@ public sealed class TileSpawningUIController : UIController
     private readonly List<ITileDefinition> _shownTiles = new();
     private bool _clearingTileSelections;
     private bool _eraseTile;
+    private bool _mirrorableTile; // Tracks if the chosen tile even can be mirrored.
+    private bool _mirroredTile;
 
     public override void Initialize()
     {
         DebugTools.Assert(_init == false);
         _init = true;
         _placement.PlacementChanged += ClearTileSelection;
+        _placement.DirectionChanged += OnDirectionChanged;
+        _placement.MirroredChanged += OnMirroredChanged;
     }
 
     private void StartTilePlacement(int tileType)
     {
         var newObjInfo = new PlacementInformation
         {
-            PlacementOption = "AlignTileAny",
+            PlacementOption = nameof(AlignTileAny),
             TileType = tileType,
             Range = 400,
             IsTile = true
@@ -67,6 +73,17 @@ public sealed class TileSpawningUIController : UIController
         args.Button.Pressed = args.Pressed;
     }
 
+    private void OnTileMirroredToggled(ButtonToggledEventArgs args)
+    {
+        if (_window == null || _window.Disposed)
+            return;
+
+        _placement.Mirrored = args.Pressed;
+        _mirroredTile = _placement.Mirrored;
+
+        args.Button.Pressed = args.Pressed;
+    }
+
     public void ToggleWindow()
     {
         EnsureWindow();
@@ -78,6 +95,9 @@ public sealed class TileSpawningUIController : UIController
         else
         {
             _window.Open();
+            UpdateEntityDirectionLabel();
+            UpdateMirroredButton();
+            _window.SearchBar.GrabKeyboardFocus();
         }
     }
 
@@ -93,6 +113,10 @@ public sealed class TileSpawningUIController : UIController
         _window.TileList.OnItemDeselected += OnTileItemDeselected;
         _window.EraseButton.Pressed = _eraseTile;
         _window.EraseButton.OnToggled += OnTileEraseToggled;
+        _window.MirroredButton.Disabled = !_mirrorableTile;
+        _window.RotationLabel.FontColorOverride = _mirrorableTile ? Color.White : Color.Gray;
+        _window.MirroredButton.Pressed = _mirroredTile;
+        _window.MirroredButton.OnToggled += OnTileMirroredToggled;
         BuildTileList();
     }
 
@@ -110,6 +134,7 @@ public sealed class TileSpawningUIController : UIController
         _window.TileList.ClearSelected();
         _clearingTileSelections = false;
         _window.EraseButton.Pressed = false;
+        _window.MirroredButton.Pressed = _placement.Mirrored;
     }
 
     private void OnTileClearPressed(ButtonEventArgs args)
@@ -137,6 +162,7 @@ public sealed class TileSpawningUIController : UIController
     {
         var definition = _shownTiles[args.ItemIndex];
         StartTilePlacement(definition.TileId);
+        UpdateMirroredButton();
     }
 
     private void OnTileItemDeselected(ItemList.ItemListDeselectedEventArgs args)
@@ -149,6 +175,41 @@ public sealed class TileSpawningUIController : UIController
         _placement.Clear();
     }
 
+    private void OnDirectionChanged(object? sender, EventArgs e)
+    {
+        UpdateEntityDirectionLabel();
+    }
+
+    private void UpdateEntityDirectionLabel()
+    {
+        if (_window == null || _window.Disposed)
+            return;
+
+        _window.RotationLabel.Text = _placement.Direction.ToString();
+    }
+
+    private void OnMirroredChanged(object? sender, EventArgs e)
+    {
+        UpdateMirroredButton();
+    }
+
+    private void UpdateMirroredButton()
+    {
+        if (_window == null || _window.Disposed)
+            return;
+
+        if (_placement.CurrentPermission != null && _placement.CurrentPermission.IsTile)
+        {
+            var allowed = _tiles[_placement.CurrentPermission.TileType].AllowRotationMirror;
+            _mirrorableTile = allowed;
+            _window.MirroredButton.Disabled = !_mirrorableTile;
+            _window.RotationLabel.FontColorOverride = _mirrorableTile ? Color.White : Color.Gray;
+        }
+
+        _mirroredTile = _placement.Mirrored;
+        _window.MirroredButton.Pressed = _mirroredTile;
+    }
+
     private void BuildTileList(string? searchStr = null)
     {
         if (_window == null || _window.Disposed) return;

Robust.Client/UserInterface/Controls/ItemList.cs

@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using System.Diagnostics.Contracts;
 using System.Numerics;
 using Robust.Client.Graphics;
+using Robust.Shared.Collections;
 using Robust.Shared.Graphics;
 using Robust.Shared.Input;
 using Robust.Shared.Maths;
@@ -83,9 +84,23 @@ namespace Robust.Client.UserInterface.Controls
             _updateScrollbarVisibility();
         }
 
+        public void Add(IEnumerable<Item> items)
+        {
+            foreach (var item in items)
+            {
+                if(item.Owner != this) throw new ArgumentException("Item is owned by another ItemList!");
+
+                _itemList.Add(item);
+
+                item.OnSelected += Select;
+                item.OnDeselected += Deselect;
+            }
+
+            Recalculate();
+        }
+
         public void Add(Item item)
         {
-            if (item == null) return;
             if(item.Owner != this) throw new ArgumentException("Item is owned by another ItemList!");
 
             _itemList.Add(item);
@@ -93,9 +108,19 @@ namespace Robust.Client.UserInterface.Controls
             item.OnSelected += Select;
             item.OnDeselected += Deselect;
 
-            RecalculateContentHeight();
-            if (_isAtBottom && ScrollFollowing)
-                _scrollBar.MoveToEnd();
+            Recalculate();
+        }
+
+        public void AddItems(IEnumerable<string> texts, Texture? icon = null, bool selectable = true, object? metadata = null)
+        {
+            var items = new ValueList<Item>();
+
+            foreach (var text in texts)
+            {
+                items.Add(new Item(this) {Text = text, Icon = icon, Selectable = selectable, Metadata = metadata});
+            }
+
+            Add(items);
         }
 
         public Item AddItem(string text, Texture? icon = null, bool selectable = true, object? metadata = null)
@@ -107,11 +132,15 @@ namespace Robust.Client.UserInterface.Controls
 
         public void Clear()
         {
-            foreach (var item in _itemList.ToArray())
+            // Handle this manually so we can just clear all at once.
+            foreach (var item in _itemList)
             {
-                Remove(item);
+                item.OnSelected -= Select;
+                item.OnDeselected -= Deselect;
             }
 
+            _itemList.Clear();
+            Recalculate();
             _totalContentHeight = 0;
         }
 
@@ -125,25 +154,35 @@ namespace Robust.Client.UserInterface.Controls
             _itemList.CopyTo(array, arrayIndex);
         }
 
+        private void InternalRemoveAt(int index)
+        {
+            if (_itemList.Count <= index)
+                return;
+
+            // If you modify this then also make sure to update Clear!
+            var item = _itemList[index];
+            _itemList.RemoveAt(index);
+
+            item.OnSelected -= Select;
+            item.OnDeselected -= Deselect;
+        }
+
         public bool Remove(Item item)
         {
-            if (item == null) return false;
-
             var value =  _itemList.Remove(item);
 
             item.OnSelected -= Select;
             item.OnDeselected -= Deselect;
 
-            RecalculateContentHeight();
-            if (_isAtBottom && ScrollFollowing)
-                _scrollBar.MoveToEnd();
+            Recalculate();
 
             return value;
         }
 
         public void RemoveAt(int index)
         {
-            Remove(this[index]);
+            InternalRemoveAt(index);
+            Recalculate();
         }
 
         public IEnumerator<Item> GetEnumerator()
@@ -161,16 +200,24 @@ namespace Robust.Client.UserInterface.Controls
             return _itemList.IndexOf(item);
         }
 
-        public void Insert(int index, Item item)
+        private void InternalInsert(int index, Item item)
         {
-            if (item == null) return;
             if(item.Owner != this) throw new ArgumentException("Item is owned by another ItemList!");
 
             _itemList.Insert(index, item);
 
             item.OnSelected += Select;
             item.OnDeselected += Deselect;
+        }
 
+        public void Insert(int index, Item item)
+        {
+            InternalInsert(index, item);
+            Recalculate();
+        }
+
+        private void Recalculate()
+        {
             RecalculateContentHeight();
             if (_isAtBottom && ScrollFollowing)
                 _scrollBar.MoveToEnd();
@@ -191,7 +238,6 @@ namespace Robust.Client.UserInterface.Controls
             SetItems(newItems, (a,b) => string.Compare(a.Text, b.Text));
         }
 
-        /// <inheritdoc />
         /// <summary>
         /// This variant allows for a custom equality operator to compare items, when
         /// comparing the Item text is not desired.
@@ -215,13 +261,13 @@ namespace Robust.Client.UserInterface.Controls
                 else if (cmpResult > 0)
                 {
                     // Item exists in our list, but not in `newItems`. Remove it.
-                    RemoveAt(i);
+                    InternalRemoveAt(i);
                     i--;
                 }
                 else if (cmpResult < 0)
                 {
                     // A new entry which doesn't exist in our list. Insert it.
-                    Insert(i + 1, newItems[j]);
+                    InternalInsert(i + 1, newItems[j]);
                     j--;
                 }
             }
@@ -229,16 +275,18 @@ namespace Robust.Client.UserInterface.Controls
             // Any remaining items in our list don't exist in `newItems` so remove them
             while (i >= 0)
             {
-                RemoveAt(i);
+                InternalRemoveAt(i);
                 i--;
             }
 
             // And finally, any remaining items in `newItems` don't exist in our list. Create them.
             while (j >= 0)
             {
-                Insert(0, newItems[j]);
+                InternalInsert(0, newItems[j]);
                 j--;
             }
+
+            Recalculate();
         }
 
         // Without this attribute, this would compile into a property called "Item", causing problems with the Item class.
@@ -290,9 +338,12 @@ namespace Robust.Client.UserInterface.Controls
 
         public void ClearSelected(int? except = null)
         {
-            foreach (var item in GetSelected())
+            for (var i = 0; i < _itemList.Count; i++)
             {
-                if(IndexOf(item) == except) continue;
+                if (i == except)
+                    continue;
+
+                var item = _itemList[i];
                 item.Selected = false;
             }
         }
@@ -690,7 +741,7 @@ namespace Robust.Client.UserInterface.Controls
                 get => _selected;
                 set
                 {
-                    if (!Selectable) return;
+                    if (!Selectable || _selected == value) return;
                     _selected = value;
                     if(_selected) OnSelected?.Invoke(this);
                     else OnDeselected?.Invoke(this);

Robust.Client/UserInterface/CustomControls/TileSpawnWindow.xaml

@@ -10,7 +10,9 @@
         </BoxContainer>
         <ItemList Name="TileList" Access="Public" VerticalExpand="True"/>
         <BoxContainer Orientation="Horizontal">
+            <Button Name="MirroredButton" Access="Public" ToggleMode="True" Text="{Loc tile-spawn-window-mirror-button-text}"/>
             <Button Name="EraseButton" Access="Public" ToggleMode="True" Text="{Loc window-erase-button-text}"/>
         </BoxContainer>
+        <Label Name="RotationLabel" Access="Public"/>
     </BoxContainer>
 </TileSpawnWindow>

Robust.Client/UserInterface/DevWindow/DevWindow.xaml

@@ -5,5 +5,6 @@
         <DebugConsole Name="DebugConsole" />
         <DevWindowTabUI Name="UI" />
         <DevWindowTabPerf Name="Perf" />
+        <DevWindowTabTextures Name="Textures" />
     </TabContainer>
 </Control>

Robust.Client/UserInterface/DevWindow/DevWindow.xaml.cs

@@ -8,6 +8,7 @@ using Robust.Client.UserInterface.Stylesheets;
 using Robust.Client.UserInterface.XAML;
 using Robust.Shared.Console;
 using Robust.Shared.IoC;
+using Robust.Shared.Localization;
 
 namespace Robust.Client.UserInterface
 {
@@ -26,6 +27,7 @@ namespace Robust.Client.UserInterface
             TabContainer.SetTabTitle(DebugConsole, "Debug Console");
             TabContainer.SetTabTitle(UI, "User Interface");
             TabContainer.SetTabTitle(Perf, "Profiling");
+            TabContainer.SetTabTitle(Textures, Loc.GetString("dev-window-tab-textures-title"));
 
             Stylesheet =
                 new DefaultStylesheet(IoCManager.Resolve<IResourceCache>(), IoCManager.Resolve<IUserInterfaceManager>()).Stylesheet;

Robust.Client/UserInterface/DevWindow/DevWindowTabTextures.xaml

@@ -0,0 +1,26 @@
+<Control xmlns="https://spacestation14.io"
+         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+         x:Class="Robust.Client.UserInterface.DevWindowTabTextures">
+    <SplitContainer Orientation="Horizontal">
+        <!-- Left pane: list of textures -->
+        <BoxContainer Orientation="Vertical" MinWidth="200">
+            <Button Name="ReloadButton" Text="{Loc 'dev-window-tab-textures-reload'}" />
+            <LineEdit Name="SearchBar" PlaceHolder="{Loc 'dev-window-tab-textures-filter'}" />
+
+            <ScrollContainer HScrollEnabled="False" VerticalExpand="True">
+                <BoxContainer Name="TextureList" Orientation="Vertical" />
+            </ScrollContainer>
+
+            <Label Name="SummaryLabel" Margin="4" />
+        </BoxContainer>
+
+        <!-- Right pane: show the selected texture info -->
+        <Control MinWidth="400">
+            <BoxContainer Orientation="Vertical">
+                <TextureRect Name="SelectedTextureDisplay" VerticalExpand="True" CanShrink="True"
+                             Stretch="KeepAspectCentered" />
+                <Label Name="SelectedTextureInfo" />
+            </BoxContainer>
+        </Control>
+    </SplitContainer>
+</Control>

Robust.Client/UserInterface/DevWindow/DevWindowTabTextures.xaml.cs

@@ -0,0 +1,136 @@
+using System;
+using System.Linq;
+using Robust.Client.AutoGenerated;
+using Robust.Client.Graphics;
+using Robust.Client.Graphics.Clyde;
+using Robust.Client.UserInterface.Controls;
+using Robust.Client.UserInterface.XAML;
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+using Robust.Shared.Utility;
+
+namespace Robust.Client.UserInterface;
+
+/// <summary>
+/// Shows all loaded textures in the game.
+/// </summary>
+[GenerateTypedNameReferences]
+internal sealed partial class DevWindowTabTextures : Control
+{
+    [Dependency] private readonly IClydeInternal _clyde = null!;
+    [Dependency] private readonly ILocalizationManager _loc = null!;
+
+    public DevWindowTabTextures()
+    {
+        RobustXamlLoader.Load(this);
+        IoCManager.InjectDependencies(this);
+
+        ReloadButton.OnPressed += _ => Reload();
+        SearchBar.OnTextChanged += _ => Reload();
+    }
+
+    protected override void VisibilityChanged(bool newVisible)
+    {
+        if (newVisible)
+        {
+            Reload();
+        }
+        else
+        {
+            // Clear to release memory when tab not visible.
+            Clear();
+        }
+    }
+
+    private void Clear()
+    {
+        TextureList.RemoveAllChildren();
+    }
+
+    private void Reload()
+    {
+        Clear();
+
+        var total = 0L;
+
+        foreach (var (clydeTexture, loadedTexture) in _clyde.GetLoadedTextures()
+                     .OrderByDescending(tup => tup.Item2.MemoryPressure))
+        {
+            if (!string.IsNullOrWhiteSpace(SearchBar.Text))
+            {
+                if (loadedTexture.Name is not { } name)
+                    continue;
+
+                if (!name.Contains(SearchBar.Text, StringComparison.CurrentCultureIgnoreCase))
+                    continue;
+            }
+
+            if (loadedTexture.MemoryPressure == 0)
+            {
+                // Bad hack to avoid showing render targets lol.
+                continue;
+            }
+
+            var button = new ContainerButton
+            {
+                Children = { new TextureEntry(loadedTexture, clydeTexture) }
+            };
+            button.OnPressed += _ => SelectTexture(loadedTexture, clydeTexture);
+
+            TextureList.AddChild(button);
+
+            total += loadedTexture.MemoryPressure;
+        }
+
+        SummaryLabel.Text =
+            _loc.GetString("dev-window-tab-textures-summary", ("bytes", ByteHelpers.FormatBytes(total)));
+    }
+
+    private void SelectTexture(Clyde.LoadedTexture loaded, Clyde.ClydeTexture texture)
+    {
+        SelectedTextureDisplay.Texture = texture;
+        SelectedTextureInfo.Text = _loc.GetString("dev-window-tab-textures-info",
+            ("width", loaded.Width),
+            ("height", loaded.Height),
+            ("pixelType", loaded.TexturePixelType),
+            ("srgb", loaded.IsSrgb),
+            ("name", loaded.Name ?? ""),
+            ("bytes", ByteHelpers.FormatBytes(loaded.MemoryPressure)));
+    }
+
+    private sealed class TextureEntry : Control
+    {
+        public TextureEntry(Clyde.LoadedTexture loaded, Clyde.ClydeTexture texture)
+        {
+            SetHeight = 64;
+
+            var bytes = ByteHelpers.FormatBytes(loaded.MemoryPressure);
+
+            var label = loaded.Name == null
+                ? $"{texture.TextureId} ({bytes})"
+                : $"{loaded.Name}\n{texture.TextureId} ({bytes})";
+
+            AddChild(new BoxContainer
+            {
+                Orientation = BoxContainer.LayoutOrientation.Horizontal,
+                Children =
+                {
+                    new TextureRect
+                    {
+                        SetWidth = 64,
+                        Texture = texture,
+                        CanShrink = true,
+                        RectClipContent = true,
+                        Stretch = TextureRect.StretchMode.Scale
+                    },
+                    new Label
+                    {
+                        Text = label,
+                        ClipText = true,
+                        HorizontalExpand = true
+                    }
+                }
+            });
+        }
+    }
+}

Robust.Client/UserInterface/UIConstants.cs

@@ -0,0 +1,7 @@
+namespace Robust.Client.UserInterface;
+
+internal static class UIConstants
+{
+    public const string ObsoleteInheritanceMessage =
+        "Do not inherit from standard UI controls, compose via nesting instead";
+}

Robust.Client/UserInterface/UserInterfaceManager.Input.cs

@@ -103,7 +103,6 @@ internal partial class UserInterfaceManager
             return;
         }
 
-
         var guiArgs = new GUIBoundKeyEventArgs(args.Function, args.State, args.PointerLocation, args.CanFocus,
             args.PointerLocation.Position / control.UIScale - control.GlobalPosition,
             args.PointerLocation.Position - control.GlobalPixelPosition);
@@ -115,10 +114,6 @@ internal partial class UserInterfaceManager
             args.Handle();
         }
 
-        // Attempt to ensure that keybind-up events get raised after a keybind-down.
-        DebugTools.Assert(!_focusedControls.TryGetValue(args.Function, out var existing)
-                          || !existing.VisibleInTree
-                          || args.IsRepeat && existing == control);
         _focusedControls[args.Function] = control;
 
         OnKeyBindDown?.Invoke(control);

Robust.Client/UserInterface/UserInterfaceManager.Layout.cs

@@ -5,9 +5,9 @@ using Robust.Client.Graphics;
 using Robust.Client.UserInterface.Controls;
 using Robust.Client.UserInterface.CustomControls;
 using Robust.Shared.Localization;
-using Robust.Shared.Log;
 using Robust.Shared.Maths;
 using Robust.Shared.Profiling;
+using Robust.Shared.Utility;
 
 namespace Robust.Client.UserInterface;
 internal sealed partial class UserInterfaceManager
@@ -61,7 +61,7 @@ internal sealed partial class UserInterfaceManager
                 Title = string.IsNullOrEmpty(title) ? Loc.GetString("popup-title") : title,
             };
 
-            var label = new Label { Text = contents };
+            var label = new RichTextLabel { Text = $"[color=white]{FormattedMessage.EscapeText(contents)}[/color]" };
 
             var vBox = new BoxContainer
             {

Robust.Client/Utility/ReloadManager.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 using System.Threading;
 using Robust.Client.Graphics;
 using Robust.Shared;
@@ -21,12 +20,14 @@ internal sealed class ReloadManager : IReloadManager
     [Dependency] private readonly IConfigurationManager _cfg = default!;
     [Dependency] private readonly ILogManager _logMan = default!;
     [Dependency] private readonly IResourceManager _res = default!;
+#pragma warning disable CS0414
     [Dependency] private readonly ITaskManager _tasks = default!;
+#pragma warning restore CS0414
 
     private readonly TimeSpan _reloadDelay = TimeSpan.FromMilliseconds(10);
     private CancellationTokenSource _reloadToken = new();
     private readonly HashSet<ResPath> _reloadQueue = new();
-    private List<FileSystemWatcher> _watchers = new();
+    private List<FileSystemWatcher> _watchers = new(); // this list is never used but needed to prevent them from being garbage collected
 
     public event Action<ResPath>? OnChanged;
 
@@ -69,6 +70,11 @@ internal sealed class ReloadManager : IReloadManager
         _reloadQueue.Clear();
     }
 
+    public void Register(ResPath directory, string filter)
+    {
+        Register(directory.ToString(), filter);
+    }
+
     public void Register(string directory, string filter)
     {
         if (!_cfg.GetCVar(CVars.ResPrototypeReloadWatch))
@@ -90,7 +96,7 @@ internal sealed class ReloadManager : IReloadManager
                 NotifyFilter = NotifyFilters.LastWrite
             };
 
-            _watchers.Add(watcher);
+            _watchers.Add(watcher); // prevent garbage collection
 
             watcher.Changed += OnWatch;
 
@@ -100,7 +106,7 @@ internal sealed class ReloadManager : IReloadManager
             }
             catch (IOException ex)
             {
-                Logger.Error($"Watching resources in path {path} threw an exception:\n{ex}");
+                _sawmill.Error($"Watching resources in path {path} threw an exception:\n{ex}");
             }
         }
 
@@ -136,6 +142,6 @@ internal sealed class ReloadManager : IReloadManager
                 }
             });
         }
-        #endif
+#endif
     }
 }

Robust.Client/ViewVariables/ViewVariablesAddWindow.xaml.cs

@@ -2,11 +2,15 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Numerics;
+using System.Threading;
 using Robust.Client.AutoGenerated;
 using Robust.Client.UserInterface.Controls;
 using Robust.Client.UserInterface.CustomControls;
 using Robust.Client.UserInterface.XAML;
+using Robust.Shared.Collections;
 using Robust.Shared.Localization;
+using Robust.Shared.Log;
+using Robust.Shared.Timing;
 
 namespace Robust.Client.ViewVariables
 {
@@ -51,15 +55,19 @@ namespace Robust.Client.ViewVariables
             _lastSearch = search;
             EntryItemList.ClearSelected();
             EntryItemList.Clear();
+
             AddButton.Disabled = true;
+            var items = new ValueList<string>();
 
             foreach (var component in _entries)
             {
                 if(!string.IsNullOrEmpty(search) && !component.Contains(search, StringComparison.InvariantCultureIgnoreCase))
                     continue;
 
-                EntryItemList.AddItem(component);
+                items.Add(component);
             }
+
+            EntryItemList.AddItems(items);
         }
 
         private void OnSearchTextChanged(LineEdit.LineEditEventArgs obj)

Robust.Roslyn.Shared/Diagnostics.cs

@@ -37,6 +37,8 @@ public static class Diagnostics
     public const string IdPreferOtherType = "RA0031";
     public const string IdDuplicateDependency = "RA0032";
     public const string IdForbidLiteral = "RA0033";
+    public const string IdObsoleteInheritance = "RA0034";
+    public const string IdObsoleteInheritanceWithMessage = "RA0035";
 
     public static SuppressionDescriptor MeansImplicitAssignment =>
         new SuppressionDescriptor("RADC1000", "CS0649", "Marked as implicitly assigned.");

Robust.Server/BaseServer.cs

@@ -331,6 +331,7 @@ namespace Robust.Server
             // TODO: solve this properly.
             _serializer.Initialize();
 
+            _loc.Initialize();
             _loc.AddLoadedToStringSerializer(_stringSerializer);
 
             //IoCManager.Resolve<IMapLoader>().LoadedMapData +=

Robust.Server/Console/Commands/ScaleCommand.cs

@@ -4,6 +4,7 @@ using Robust.Server.GameObjects;
 using Robust.Shared.Console;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Localization;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 using Robust.Shared.Physics.Collision.Shapes;
@@ -16,6 +17,20 @@ public sealed class ScaleCommand : LocalizedCommands
     [Dependency] private readonly IEntityManager _entityManager = default!;
 
     public override string Command => "scale";
+
+    public override CompletionResult GetCompletion(IConsoleShell shell, string[] args)
+    {
+        switch (args.Length)
+        {
+            case 1:
+                return CompletionResult.FromOptions(CompletionHelper.NetEntities(args[0], entManager: _entityManager));
+            case 2:
+                return CompletionResult.FromHint(Loc.GetString("cmd-hint-float"));
+            default:
+                return CompletionResult.Empty;
+        }
+    }
+
     public override void Execute(IConsoleShell shell, string argStr, string[] args)
     {
         if (args.Length != 2)

Robust.Server/GameObjects/EntitySystems/PointLightSystem.cs

@@ -14,6 +14,19 @@ public sealed class PointLightSystem : SharedPointLightSystem
         base.Initialize();
         SubscribeLocalEvent<PointLightComponent, ComponentGetState>(OnLightGetState);
         SubscribeLocalEvent<PointLightComponent, ComponentStartup>(OnLightStartup);
+        SubscribeLocalEvent<PointLightComponent, ComponentShutdown>(OnLightShutdown);
+        SubscribeLocalEvent<PointLightComponent, MetaFlagRemoveAttemptEvent>(OnFlagRemoveAttempt);
+    }
+
+    private void OnLightShutdown(Entity<PointLightComponent> ent, ref ComponentShutdown args)
+    {
+        UpdatePriority(ent.Owner, ent.Comp, MetaData(ent.Owner));
+    }
+
+    private void OnFlagRemoveAttempt(Entity<PointLightComponent> ent, ref MetaFlagRemoveAttemptEvent args)
+    {
+        if (IsHighPriority(ent.Comp))
+            args.ToRemove &= ~MetaDataFlags.PvsPriority;
     }
 
     private void OnLightStartup(EntityUid uid, PointLightComponent component, ComponentStartup args)
@@ -21,24 +34,14 @@ public sealed class PointLightSystem : SharedPointLightSystem
         UpdatePriority(uid, component, MetaData(uid));
     }
 
-    protected override void UpdatePriority(EntityUid uid, SharedPointLightComponent comp, MetaDataComponent meta)
+    private bool IsHighPriority(SharedPointLightComponent comp)
     {
-        var isHighPriority = comp.Enabled && comp.CastShadows && (comp.Radius > 7);
-        _metadata.SetFlag((uid, meta), MetaDataFlags.PvsPriority, isHighPriority);
+        return comp is {Enabled: true, CastShadows: true, Radius: > 7, LifeStage: <= ComponentLifeStage.Running};
     }
 
-    private void OnLightGetState(EntityUid uid, PointLightComponent component, ref ComponentGetState args)
+    protected override void UpdatePriority(EntityUid uid, SharedPointLightComponent comp, MetaDataComponent meta)
     {
-        args.State = new PointLightComponentState()
-        {
-            Color = component.Color,
-            Enabled = component.Enabled,
-            Energy = component.Energy,
-            Offset = component.Offset,
-            Radius = component.Radius,
-            Softness = component.Softness,
-            CastShadows = component.CastShadows,
-        };
+        _metadata.SetFlag((uid, meta), MetaDataFlags.PvsPriority, IsHighPriority(comp));
     }
 
     public override SharedPointLightComponent EnsureLight(EntityUid uid)

Robust.Server/GameObjects/EntitySystems/ServerOccluderSystem.cs

@@ -9,12 +9,30 @@ public sealed class ServerOccluderSystem : OccluderSystem
 {
     [Dependency] private readonly MetaDataSystem _metadata = default!;
 
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<OccluderComponent, MetaFlagRemoveAttemptEvent>(OnFlagRemoveAttempt);
+    }
+
+    private void OnFlagRemoveAttempt(Entity<OccluderComponent> ent, ref MetaFlagRemoveAttemptEvent args)
+    {
+        if (ent.Comp is {Enabled: true, LifeStage: <= ComponentLifeStage.Running})
+            args.ToRemove &= ~MetaDataFlags.PvsPriority;
+    }
+
     protected override void OnCompStartup(EntityUid uid, OccluderComponent component, ComponentStartup args)
     {
         base.OnCompStartup(uid, component, args);
         _metadata.SetFlag(uid, MetaDataFlags.PvsPriority, component.Enabled);
     }
 
+    protected override void OnCompRemoved(EntityUid uid, OccluderComponent component, ComponentRemove args)
+    {
+        base.OnCompRemoved(uid, component, args);
+        _metadata.SetFlag(uid, MetaDataFlags.PvsPriority, false);
+    }
+
     public override void SetEnabled(EntityUid uid, bool enabled, OccluderComponent? comp = null, MetaDataComponent? meta = null)
     {
         if (!Resolve(uid, ref comp, false))

Robust.Server/GameStates/PvsData.cs

@@ -204,7 +204,7 @@ internal struct PvsMetadata
     {
         DebugTools.AssertEqual(NetEntity, comp.NetEntity);
         DebugTools.AssertEqual(VisMask, comp.VisibilityMask);
-        DebugTools.Assert(LifeStage == comp.EntityLifeStage);
+        DebugTools.AssertEqual(LifeStage, comp.EntityLifeStage);
         DebugTools.Assert(LastModifiedTick == comp.EntityLastModifiedTick || LastModifiedTick.Value == 0);
     }
 }

Robust.Server/GameStates/PvsSystem.Chunks.cs

@@ -166,11 +166,11 @@ internal sealed partial class PvsSystem
         var session = pvsSession.Session;
         if (session.Status != SessionStatus.InGame)
         {
-            pvsSession.Viewers  = Array.Empty<Entity<TransformComponent, EyeComponent?>>();
+            pvsSession.Viewers = Array.Empty<Entity<TransformComponent, EyeComponent?>>();
             return;
         }
 
-        // Fast path
+        // The majority of players will have no view subscriptions
         if (session.ViewSubscriptions.Count == 0)
         {
             if (session.AttachedEntity is not {} attached)
@@ -184,15 +184,21 @@ internal sealed partial class PvsSystem
             return;
         }
 
+        var count = session.ViewSubscriptions.Count;
         var i = 0;
         if (session.AttachedEntity is { } local)
         {
-            Array.Resize(ref pvsSession.Viewers, session.ViewSubscriptions.Count + 1);
+            if (!session.ViewSubscriptions.Contains(local))
+                count += 1;
+
+            Array.Resize(ref pvsSession.Viewers, count);
+
+            // Attached entity is always the first viewer, to prioritize it and help reduce pop-in for the "main" eye.
             pvsSession.Viewers[i++] = (local, Transform(local), _eyeQuery.CompOrNull(local));
         }
         else
         {
-            Array.Resize(ref pvsSession.Viewers, session.ViewSubscriptions.Count);
+            Array.Resize(ref pvsSession.Viewers, count);
         }
 
         foreach (var ent in session.ViewSubscriptions)
@@ -200,6 +206,8 @@ internal sealed partial class PvsSystem
             if (ent != session.AttachedEntity)
                 pvsSession.Viewers[i++] =  (ent, Transform(ent), _eyeQuery.CompOrNull(ent));
         }
+
+        DebugTools.AssertEqual(i, pvsSession.Viewers.Length);
     }
 
     private void ProcessVisibleChunks()

Robust.Server/Localization/ServerLocalizationManager.cs

@@ -0,0 +1,8 @@
+using Robust.Shared.Localization;
+
+namespace Robust.Server.Localization;
+
+internal sealed class ServerLocalizationManager : LocalizationManager, ILocalizationManager
+{
+    void ILocalizationManager.Initialize() => Initialize();
+}

Robust.Server/Physics/GridFixtureSystem.cs

@@ -268,7 +268,6 @@ namespace Robust.Server.Physics
                     newGrids[i] = newGridUid;
 
                     // Keep same origin / velocity etc; this makes updating a lot faster and easier.
-                    _xformSystem.SetWorldPosition(newGridXform, gridPos);
                     _xformSystem.SetWorldPositionRotation(newGridUid, gridPos, gridRot, newGridXform);
                     var splitBody = _bodyQuery.GetComponent(newGridUid);
                     _physics.SetLinearVelocity(newGridUid, mapBody.LinearVelocity, body: splitBody);
@@ -290,7 +289,7 @@ namespace Robust.Server.Physics
                     }
 
                     _maps.SetTiles(newGrid.Owner, newGrid.Comp, tileData);
-                    DebugTools.Assert(_mapManager.IsGrid(newGridUid), "A split grid had no tiles?");
+                    DebugTools.Assert(_gridQuery.HasComp(newGridUid), "A split grid had no tiles?");
 
                     // Set tiles on new grid + update anchored entities
                     foreach (var node in group)

Robust.Server/Placement/PlacementManager.cs

@@ -179,11 +179,14 @@ namespace Robust.Server.Placement
             }
             else
             {
-                PlaceNewTile(tileType, coordinates, msg.MsgChannel.UserId);
+                if (_tileDefinitionManager[tileType].AllowRotationMirror)
+                    PlaceNewTile(tileType, coordinates, msg.MsgChannel.UserId, Tile.DirectionToByte(dirRcv), msg.Mirrored);
+                else
+                    PlaceNewTile(tileType, coordinates, msg.MsgChannel.UserId, Tile.DirectionToByte(Direction.South), false);
             }
         }
 
-        private void PlaceNewTile(int tileType, EntityCoordinates coordinates, NetUserId placingUserId)
+        private void PlaceNewTile(int tileType, EntityCoordinates coordinates, NetUserId placingUserId, byte direction, bool mirrored)
         {
             if (!coordinates.IsValid(_entityManager)) return;
 
@@ -193,7 +196,7 @@ namespace Robust.Server.Placement
             if (_entityManager.TryGetComponent(coordinates.EntityId, out grid)
                 || _mapManager.TryFindGridAt(_xformSystem.ToMapCoordinates(coordinates), out gridId, out grid))
             {
-                _maps.SetTile(gridId, grid, coordinates, new Tile(tileType));
+                _maps.SetTile(gridId, grid, coordinates, new Tile(tileType, rotationMirroring: (byte)(direction + (mirrored ? 4 : 0))));
 
                 var placementEraseEvent = new PlacementTileEvent(tileType, coordinates, placingUserId);
                 _entityManager.EventBus.RaiseEvent(EventSource.Local, placementEraseEvent);
@@ -207,7 +210,7 @@ namespace Robust.Server.Placement
 
                 _xformSystem.SetWorldPosition(newGridXform, coordinates.Position - newGrid.Comp.TileSizeHalfVector); // assume bottom left tile origin
                 var tilePos = _maps.WorldToTile(newGrid.Owner, newGrid.Comp, coordinates.Position);
-                _maps.SetTile(newGrid.Owner, newGrid.Comp, tilePos, new Tile(tileType));
+                _maps.SetTile(newGrid.Owner, newGrid.Comp, tilePos, new Tile(tileType, rotationMirroring: (byte)(direction + (mirrored ? 4 : 0))));
 
                 var placementEraseEvent = new PlacementTileEvent(tileType, coordinates, placingUserId);
                 _entityManager.EventBus.RaiseEvent(EventSource.Local, placementEraseEvent);

Robust.Server/Prototypes/ServerPrototypeManager.cs

@@ -13,8 +13,10 @@ namespace Robust.Server.Prototypes
 {
     public sealed class ServerPrototypeManager : PrototypeManager
     {
+#pragma warning disable CS0414
         [Dependency] private readonly IPlayerManager _playerManager = default!;
         [Dependency] private readonly IConGroupController _conGroups = default!;
+#pragma warning restore CS0414
         [Dependency] private readonly INetManager _netManager = default!;
         [Dependency] private readonly IBaseServerInternal _server = default!;
 

Robust.Server/ServerIoC.cs

@@ -4,6 +4,7 @@ using Robust.Server.Console;
 using Robust.Server.DataMetrics;
 using Robust.Server.GameObjects;
 using Robust.Server.GameStates;
+using Robust.Server.Localization;
 using Robust.Server.Placement;
 using Robust.Server.Player;
 using Robust.Server.Prototypes;
@@ -21,6 +22,7 @@ using Robust.Shared.Console;
 using Robust.Shared.ContentPack;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Localization;
 using Robust.Shared.Map;
 using Robust.Shared.Network;
 using Robust.Shared.Player;
@@ -97,7 +99,9 @@ namespace Robust.Server
             deps.Register<NetworkResourceManager>();
             deps.Register<IHttpClientHolder, HttpClientHolder>();
             deps.Register<UploadedContentManager>();
-             deps.Register<IHWId, DummyHWId>();
+            deps.Register<IHWId, DummyHWId>();
+            deps.Register<ILocalizationManager, ServerLocalizationManager>();
+            deps.Register<ILocalizationManagerInternal, ServerLocalizationManager>();
         }
     }
 }

Robust.Shared/Analyzers/ObsoleteInheritanceAttribute.cs

@@ -0,0 +1,28 @@
+using System;
+
+namespace Robust.Shared.Analyzers;
+
+/// <summary>
+/// Indicates that the ability to <i>inherit</i> this type is obsolete, and attempting to do so should give a warning.
+/// </summary>
+/// <remarks>
+/// This is useful to gracefully deal with types that should never have had <see cref="VirtualAttribute"/>.
+/// </remarks>
+/// <seealso cref="VirtualAttribute"/>
+[AttributeUsage(AttributeTargets.Class, Inherited = false)]
+public sealed class ObsoleteInheritanceAttribute : Attribute
+{
+    /// <summary>
+    /// An optional message provided alongside this obsoletion.
+    /// </summary>
+    public string? Message { get; }
+
+    public ObsoleteInheritanceAttribute()
+    {
+    }
+
+    public ObsoleteInheritanceAttribute(string message)
+    {
+        Message = message;
+    }
+}

Robust.Shared/Analyzers/VirtualAttribute.cs

@@ -9,6 +9,7 @@ namespace Robust.Shared.Analyzers;
 /// Robust uses analyzers to prevent accidental usage of non-sealed classes:
 /// a class must be either marked [Virtual], abstract, or sealed.
 /// </remarks>
+/// <seealso cref="ObsoleteInheritanceAttribute"/>
 [AttributeUsage(AttributeTargets.Class, Inherited = false)]
 public sealed class VirtualAttribute : Attribute
 {

Robust.Shared/CVars.cs

@@ -968,6 +968,13 @@ namespace Robust.Shared
         public static readonly CVarDef<string> RenderFOVColor =
             CVarDef.Create("render.fov_color", Color.Black.ToHex(), CVar.REPLICATED | CVar.SERVER);
 
+        /// <summary>
+        /// Whether to render tile edges, which is where some tiles can partially overlap other adjacent tiles on a grid.
+        /// E.g., snow tiles partly extending beyond their own tile to blend together with different adjacent tiles types.
+        /// </summary>
+        public static readonly CVarDef<bool> RenderTileEdges =
+            CVarDef.Create("render.tile_edges", true, CVar.CLIENTONLY);
+
         /*
          *  CONTROLS
          */

Robust.Shared/ComponentTrees/RecursiveMoveSystem.cs

@@ -1,6 +1,7 @@
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
+using Robust.Shared.Map.Components;
 using Robust.Shared.Utility;
 
 namespace Robust.Shared.ComponentTrees;
@@ -13,20 +14,23 @@ namespace Robust.Shared.ComponentTrees;
 /// </remarks>
 internal sealed class RecursiveMoveSystem : EntitySystem
 {
-    [Dependency] private readonly IMapManager _mapManager = default!;
     [Dependency] private readonly SharedTransformSystem _transform = default!;
 
     public delegate void TreeRecursiveMoveEventHandler(EntityUid uid, TransformComponent xform);
 
     public event TreeRecursiveMoveEventHandler? OnTreeRecursiveMove;
 
+    private EntityQuery<MapComponent> _mapQuery;
+    private EntityQuery<MapGridComponent> _gridQuery;
     private EntityQuery<TransformComponent> _xformQuery;
 
-    bool _subscribed = false;
+    private bool _subscribed = false;
 
     public override void Initialize()
     {
         base.Initialize();
+        _gridQuery = GetEntityQuery<MapGridComponent>();
+        _mapQuery = GetEntityQuery<MapComponent>();
         _xformQuery = GetEntityQuery<TransformComponent>();
     }
 
@@ -52,8 +56,8 @@ internal sealed class RecursiveMoveSystem : EntitySystem
         if (args.Component.MapUid == args.Sender || args.Component.GridUid == args.Sender)
             return;
 
-        DebugTools.Assert(!_mapManager.IsMap(args.Sender));
-        DebugTools.Assert(!_mapManager.IsGrid(args.Sender));
+        DebugTools.Assert(!_mapQuery.HasComp(args.Sender));
+        DebugTools.Assert(!_gridQuery.HasComp(args.Sender));
 
         AnythingMovedSubHandler(args.Sender, args.Component);
     }

Robust.Shared/Console/Commands/MapCommands.cs

@@ -37,7 +37,7 @@ sealed class AddMapCommand : LocalizedEntityCommands
 
 sealed class RemoveMapCommand : LocalizedCommands
 {
-    [Dependency] private readonly IMapManager _map = default!;
+    [Dependency] private readonly IEntitySystemManager _systems = default!;
 
     public override string Command => "rmmap";
     public override bool RequireServerOrSingleplayer => true;
@@ -51,14 +51,15 @@ sealed class RemoveMapCommand : LocalizedCommands
         }
 
         var mapId = new MapId(int.Parse(args[0]));
+        var mapSystem = _systems.GetEntitySystem<SharedMapSystem>();
 
-        if (!_map.MapExists(mapId))
+        if (!mapSystem.MapExists(mapId))
         {
             shell.WriteError($"Map {mapId.Value} does not exist.");
             return;
         }
 
-        _map.DeleteMap(mapId);
+        mapSystem.DeleteMap(mapId);
         shell.WriteLine($"Map {mapId.Value} was removed.");
     }
 }

Robust.Shared/Console/Commands/TeleportCommands.cs

@@ -20,6 +20,7 @@ internal sealed class TeleportCommand : LocalizedEntityCommands
     [Dependency] private readonly IMapManager _map = default!;
     [Dependency] private readonly IEntityManager _entityManager = default!;
     [Dependency] private readonly SharedTransformSystem _transform = default!;
+    [Dependency] private readonly SharedMapSystem _mapSystem = default!;
 
     public override string Command => "tp";
     public override bool RequireServerOrSingleplayer => true;
@@ -46,7 +47,7 @@ internal sealed class TeleportCommand : LocalizedEntityCommands
         else
             mapId = transform.MapID;
 
-        if (!_map.MapExists(mapId))
+        if (!_mapSystem.MapExists(mapId))
         {
             shell.WriteError($"Map {mapId} doesn't exist!");
             return;
@@ -60,9 +61,11 @@ internal sealed class TeleportCommand : LocalizedEntityCommands
         }
         else
         {
-            var mapEnt = _map.GetMapEntityIdOrThrow(mapId);
-            _transform.SetWorldPosition((entity, transform), position);
-            _transform.SetParent(entity, transform, mapEnt);
+            if (_mapSystem.TryGetMap(mapId, out var mapEnt))
+            {
+                _transform.SetWorldPosition((entity, transform), position);
+                _transform.SetParent(entity, transform, mapEnt.Value);
+            }
         }
 
         shell.WriteLine($"Teleported {shell.Player} to {mapId}:{posX},{posY}.");

Robust.Shared/Containers/ContainerSlot.cs

@@ -71,7 +71,7 @@ namespace Robust.Shared.Containers
 
             #if DEBUG
             // TODO make this a proper debug assert when gun code no longer fudges client-side spawn prediction.
-            if (entMan.IsClientSide(toInsert) && !entMan.IsClientSide(Owner) && Manager.NetSyncEnabled)
+            if (entMan.IsClientSide(toInsert) && !entMan.IsClientSide(Owner) && Manager.NetSyncEnabled && !entMan.HasComponent<PredictedSpawnComponent>(toInsert))
                 Logger.Warning("Inserting a client-side entity into a networked container slot. This will block the container slot and may cause issues.");
             #endif
             ContainedEntity = toInsert;

Robust.Shared/Containers/Events/ContainerAttemptEvents.cs

@@ -16,6 +16,9 @@ public abstract class ContainerAttemptEventBase : CancellableEntityEventArgs
     }
 }
 
+/// <summary>
+/// Raised directed on the container when attempting to insert an entity.
+/// </summary>
 public sealed class ContainerIsInsertingAttemptEvent : ContainerAttemptEventBase
 {
     /// <summary>
@@ -23,7 +26,7 @@ public sealed class ContainerIsInsertingAttemptEvent : ContainerAttemptEventBase
     /// I.e., could the entity be inserted if the container doesn't contain anything else?
     /// </summary>
     public bool AssumeEmpty { get; set; }
-    
+
     public ContainerIsInsertingAttemptEvent(BaseContainer container, EntityUid entityUid, bool assumeEmpty)
         : base(container, entityUid)
     {
@@ -31,6 +34,9 @@ public sealed class ContainerIsInsertingAttemptEvent : ContainerAttemptEventBase
     }
 }
 
+/// <summary>
+/// Raised directed on the entity being inserted into the container.
+/// </summary>
 public sealed class ContainerGettingInsertedAttemptEvent : ContainerAttemptEventBase
 {
     /// <summary>
@@ -46,6 +52,9 @@ public sealed class ContainerGettingInsertedAttemptEvent : ContainerAttemptEvent
     }
 }
 
+/// <summary>
+/// Raised directed on the container when attempting to remove an entity.
+/// </summary>
 public sealed class ContainerIsRemovingAttemptEvent : ContainerAttemptEventBase
 {
     public ContainerIsRemovingAttemptEvent(BaseContainer container, EntityUid entityUid) : base(container, entityUid)
@@ -53,6 +62,9 @@ public sealed class ContainerIsRemovingAttemptEvent : ContainerAttemptEventBase
     }
 }
 
+/// <summary>
+/// Raised directed on the entity being removed from the container.
+/// </summary>
 public sealed class ContainerGettingRemovedAttemptEvent : ContainerAttemptEventBase
 {
     public ContainerGettingRemovedAttemptEvent(BaseContainer container, EntityUid entityUid) : base(container, entityUid)

Robust.Shared/Containers/SharedContainerSystem.cs

@@ -530,6 +530,39 @@ namespace Robust.Shared.Containers
             return false;
         }
 
+        /// <summary>
+        /// Returns the full chain of containers containing the entity passed in, from innermost to outermost.
+        /// </summary>
+        /// <remarks>
+        /// The resulting collection includes the container directly containing the entity (if any),
+        /// the container containing that container, and so on until reaching the outermost container.
+        /// </remarks>
+        public IEnumerable<BaseContainer> GetContainingContainers(Entity<TransformComponent?> ent)
+        {
+            if (!ent.Owner.IsValid())
+                yield break;
+
+            if (!Resolve(ent, ref ent.Comp))
+                yield break;
+
+            var child = ent.Owner;
+            var parent = ent.Comp.ParentUid;
+
+            while (parent.IsValid())
+            {
+                if (((MetaQuery.GetComponent(child).Flags & MetaDataFlags.InContainer) == MetaDataFlags.InContainer) &&
+                    _managerQuery.TryGetComponent(parent, out var conManager) &&
+                    TryGetContainingContainer(parent, child, out var parentContainer, conManager))
+                {
+                    yield return parentContainer;
+                }
+
+                var parentXform = TransformQuery.GetComponent(parent);
+                child = parent;
+                parent = parentXform.ParentUid;
+            }
+        }
+
         /// <summary>
         /// Gets the top-most container in the hierarchy for this entity, if it exists.
         /// </summary>

Robust.Shared/ContentPack/ResourceManager.cs

@@ -273,8 +273,6 @@ namespace Robust.Shared.ContentPack
 
         public IEnumerable<string> ContentGetDirectoryEntries(ResPath path)
         {
-            ArgumentNullException.ThrowIfNull(path, nameof(path));
-
             if (!path.IsRooted)
                 throw new ArgumentException("Path is not rooted", nameof(path));
 

Robust.Shared/ContentPack/Sandbox.yml

@@ -497,6 +497,23 @@ Types:
     DebuggerVisualizerAttribute: { All: True }
     Stopwatch: { All: True }
   System.Globalization:
+  # all the calendars are here, screw making our own.
+    Calendar: { All: True }
+    ChineseLunisolarCalendar: { All: True }
+    GregorianCalendar: { All: True }
+    HebrewCalendar: { All: True }
+    HijriCalendar: { All: True }
+    JapaneseCalendar: { All: True }
+    JapaneseLunisolarCalendar:  { All: True }
+    JulianCalendar: { All: True }
+    KoreanCalendar: { All: True }
+    KoreanLunisolarCalendar: { All: True }
+    PersianCalendar: { All: True }
+    TaiwanCalendar: { All: True }
+    TaiwanLunisolarCalendar: { All: True }
+    ThaiBuddhistCalendar: { All: True }
+    UmAlQuraCalendar: { All: True }
+ #end calendars
     CompareOptions: { }
     CultureInfo: { All: True }
     DateTimeStyles: { All: True } # Enum
@@ -896,6 +913,7 @@ Types:
   System.Threading:
     CancellationToken: { All: True }
     CancellationTokenSource: { All: True }
+    CancellationTokenRegistration: { All: True }
     Interlocked: { All: True }
     Monitor: { All: True }
   System.Web:
@@ -1071,6 +1089,7 @@ Types:
     DateTime: { All: True }
     DateTimeKind: { } # Enum
     DateTimeOffset: { All: True }
+    DayOfWeek: { } # Enum
     Decimal: { All: True }
     Delegate:
       Methods:

Robust.Shared/EntitySerialization/EntityDeserializer.cs

@@ -475,7 +475,7 @@ public sealed class EntityDeserializer :
 
         foreach (var (key, value) in tileMap.Children)
         {
-            var yamlTileId = ((ValueDataNode) key).AsInt();
+            var yamlTileId = int.Parse(key, CultureInfo.InvariantCulture);
             var tileName = ((ValueDataNode) value).Value;
             if (migrations.TryGetValue(tileName, out var @new))
                 tileName = @new;
@@ -1000,7 +1000,7 @@ public sealed class EntityDeserializer :
                 continue;
 
             DebugTools.Assert(meta.EntityLifeStage == EntityLifeStage.Initialized);
-            meta.EntityLifeStage = EntityLifeStage.MapInitialized;
+            EntMan.SetLifeStage(meta, EntityLifeStage.MapInitialized);
         }
 
         _log.Debug($"Finished flagging mapinit in {_stopwatch.Elapsed}");

Robust.Shared/EntitySerialization/EntitySerializer.cs

@@ -155,9 +155,9 @@ public sealed class EntitySerializer : ISerializationContext,
     public event IsSerializableDelegate? OnIsSerializeable;
     public delegate void IsSerializableDelegate(Entity<MetaDataComponent> ent, ref bool serializable);
 
-    public EntitySerializer(IDependencyCollection _dependency, SerializationOptions options)
+    public EntitySerializer(IDependencyCollection dependency, SerializationOptions options)
     {
-        _dependency.InjectDependencies(this);
+        dependency.InjectDependencies(this);
 
         _log = _logMan.GetSawmill("entity_serializer");
         SerializerProvider.RegisterSerializer(this);

Robust.Shared/EntitySerialization/MapChunkSerializer.cs

@@ -69,22 +69,45 @@ internal sealed class MapChunkSerializer : ITypeSerializer<MapChunk, MappingData
 
         var tileDefinitionManager = dependencies.Resolve<ITileDefinitionManager>();
 
-        node.TryGetValue(new ValueDataNode("version"), out var versionNode);
+        node.TryGetValue("version", out var versionNode);
         var version = ((ValueDataNode?) versionNode)?.AsInt() ?? 1;
 
-        for (ushort y = 0; y < chunk.ChunkSize; y++)
+        // Old map files will throw an error if they do not have a rotation/mirror byte stored.
+        if (version >= 7)
         {
-            for (ushort x = 0; x < chunk.ChunkSize; x++)
+            for (ushort y = 0; y < chunk.ChunkSize; y++)
             {
-                var id = version < 6 ? reader.ReadUInt16() : reader.ReadInt32();
-                var flags = reader.ReadByte();
-                var variant = reader.ReadByte();
+                for (ushort x = 0; x < chunk.ChunkSize; x++)
+                {
+                    var id = reader.ReadInt32();
+                    var flags = reader.ReadByte();
+                    var variant = reader.ReadByte();
+                    var rotationMirroring = reader.ReadByte();
 
-                var defName = tileMap[id];
-                id = tileDefinitionManager[defName].TileId;
+                    var defName = tileMap[id];
+                    id = tileDefinitionManager[defName].TileId;
 
-                var tile = new Tile(id, flags, variant);
-                chunk.TrySetTile(x, y, tile, out _, out _);
+                    var tile = new Tile(id, flags, variant, rotationMirroring);
+                    chunk.TrySetTile(x, y, tile, out _, out _);
+                }
+            }
+        }
+        else
+        {
+            for (ushort y = 0; y < chunk.ChunkSize; y++)
+            {
+                for (ushort x = 0; x < chunk.ChunkSize; x++)
+                {
+                    var id = version < 6 ? reader.ReadUInt16() : reader.ReadInt32();
+                    var flags = reader.ReadByte();
+                    var variant = reader.ReadByte();
+
+                    var defName = tileMap[id];
+                    id = tileDefinitionManager[defName].TileId;
+
+                    var tile = new Tile(id, flags, variant);
+                    chunk.TrySetTile(x, y, tile, out _, out _);
+                }
             }
         }
 
@@ -106,7 +129,7 @@ internal sealed class MapChunkSerializer : ITypeSerializer<MapChunk, MappingData
         var gridNode = new ValueDataNode();
         root.Add("tiles", gridNode);
 
-        root.Add("version", new ValueDataNode("6"));
+        root.Add("version", new ValueDataNode("7"));
 
         gridNode.Value = SerializeTiles(value, context as EntitySerializer);
 
@@ -116,7 +139,7 @@ internal sealed class MapChunkSerializer : ITypeSerializer<MapChunk, MappingData
     private static string SerializeTiles(MapChunk chunk, EntitySerializer? serializer)
     {
         // number of bytes written per tile, because sizeof(Tile) is useless.
-        const int structSize = 6;
+        const int structSize = 7;
 
         var nTiles = chunk.ChunkSize * chunk.ChunkSize * structSize;
         var barr = new byte[nTiles];
@@ -134,6 +157,7 @@ internal sealed class MapChunkSerializer : ITypeSerializer<MapChunk, MappingData
                         writer.Write(tile.TypeId);
                         writer.Write((byte) tile.Flags);
                         writer.Write(tile.Variant);
+                        writer.Write(tile.RotationMirroring);
                     }
                 }
                 return Convert.ToBase64String(barr);
@@ -153,6 +177,7 @@ internal sealed class MapChunkSerializer : ITypeSerializer<MapChunk, MappingData
                     writer.Write(yamlId);
                     writer.Write((byte) tile.Flags);
                     writer.Write(tile.Variant);
+                    writer.Write(tile.RotationMirroring);
                 }
             }
         }

Robust.Shared/GameObjects/Components/MetaDataComponent.cs

@@ -147,7 +147,7 @@ namespace Robust.Shared.GameObjects
         ///     The current lifetime stage of this entity. You can use this to check
         ///     if the entity is initialized or being deleted.
         /// </summary>
-        [ViewVariables]
+        [ViewVariables, Access(typeof(EntityManager), Other = AccessPermissions.ReadExecute)]
         public EntityLifeStage EntityLifeStage { get; internal set; }
 
         public MetaDataFlags Flags
@@ -238,6 +238,11 @@ namespace Robust.Shared.GameObjects
         /// a grid or map.
         /// </summary>
         PvsPriority = 1 << 4,
+
+        /// <summary>
+        /// If set, transform system will raise events directed at this entity whenever the GridUid or MapUid are modified.
+        /// </summary>
+        ExtraTransformEvents = 1 << 5,
     }
 
     /// <summary>

Robust.Shared/GameObjects/Components/PredictedSpawnComponent.cs

@@ -0,0 +1,7 @@
+namespace Robust.Shared.GameObjects;
+
+/// <summary>
+/// Indicates the attached entity was spawn predicted and should be reconciled when the server states comes in.
+/// </summary>
+[RegisterComponent]
+public sealed partial class PredictedSpawnComponent : Component;

Robust.Shared/GameObjects/Components/Transform/TransformComponent.cs

@@ -402,32 +402,6 @@ namespace Robust.Shared.GameObjects
             _entMan.EntitySysManager.GetEntitySystem<SharedTransformSystem>().AttachToGridOrMap(Owner, this);
         }
 
-        internal void UpdateChildMapIdsRecursive(
-            MapId newMapId,
-            EntityUid? newUid,
-            bool mapPaused,
-            EntityQuery<TransformComponent> xformQuery,
-            EntityQuery<MetaDataComponent> metaQuery,
-            MetaDataSystem system)
-        {
-            foreach (var child in _children)
-            {
-                //Set Paused state
-                var metaData = metaQuery.GetComponent(child);
-                system.SetEntityPaused(child, mapPaused, metaData);
-
-                var concrete = xformQuery.GetComponent(child);
-
-                concrete.MapUid = newUid;
-                concrete.MapID = newMapId;
-
-                if (concrete.ChildCount != 0)
-                {
-                    concrete.UpdateChildMapIdsRecursive(newMapId, newUid, mapPaused, xformQuery, metaQuery, system);
-                }
-            }
-        }
-
         [Obsolete("Use TransformSystem.SetParent() instead")]
         public void AttachParent(EntityUid parent)
         {

Robust.Shared/GameObjects/Entity.cs

@@ -47,9 +47,10 @@ public record struct Entity<T> : IFluentEntityUid, IAsType<EntityUid>
         comp = Comp;
     }
 
-    public EntityUid AsType() => Owner;
 
     public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T?> AsNullable() => new(Owner, Comp);
+    public EntityUid AsType() => Owner;
 }
 
 [NotYamlSerializable]
@@ -118,6 +119,8 @@ public record struct Entity<T1, T2> : IFluentEntityUid, IAsType<EntityUid>
         return new Entity<T1>(ent.Owner, ent.Comp1);
     }
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?> AsNullable() => new(Owner, Comp1, Comp2);
     public EntityUid AsType() => Owner;
 }
 
@@ -223,6 +226,8 @@ public record struct Entity<T1, T2, T3> : IFluentEntityUid, IAsType<EntityUid>
 
 #endregion
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?, T3?> AsNullable() => new(Owner, Comp1, Comp2, Comp3);
     public EntityUid AsType() => Owner;
 }
 
@@ -352,6 +357,8 @@ public record struct Entity<T1, T2, T3, T4> : IFluentEntityUid, IAsType<EntityUi
 
 #endregion
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?, T3?, T4?> AsNullable() => new(Owner, Comp1, Comp2, Comp3, Comp4);
     public EntityUid AsType() => Owner;
 }
 
@@ -505,6 +512,8 @@ public record struct Entity<T1, T2, T3, T4, T5> : IFluentEntityUid, IAsType<Enti
 
 #endregion
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?, T3?, T4?, T5?> AsNullable() => new(Owner, Comp1, Comp2, Comp3, Comp4, Comp5);
     public EntityUid AsType() => Owner;
 }
 
@@ -682,6 +691,8 @@ public record struct Entity<T1, T2, T3, T4, T5, T6> : IFluentEntityUid, IAsType<
 
 #endregion
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?, T3?, T4?, T5?, T6?> AsNullable() => new(Owner, Comp1, Comp2, Comp3, Comp4, Comp5, Comp6);
     public EntityUid AsType() => Owner;
 }
 
@@ -883,8 +894,9 @@ public record struct Entity<T1, T2, T3, T4, T5, T6, T7> : IFluentEntityUid, IAsT
 
 #endregion
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?, T3?, T4?, T5?, T6?, T7?> AsNullable() => new(Owner, Comp1, Comp2, Comp3, Comp4, Comp5, Comp6, Comp7);
     public EntityUid AsType() => Owner;
-
 }
 
 [NotYamlSerializable]
@@ -1109,5 +1121,7 @@ public record struct Entity<T1, T2, T3, T4, T5, T6, T7, T8> : IFluentEntityUid,
 
 #endregion
 
+    public override int GetHashCode() => Owner.GetHashCode();
+    public Entity<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?> AsNullable() => new(Owner, Comp1, Comp2, Comp3, Comp4, Comp5, Comp6, Comp7, Comp8);
     public EntityUid AsType() => Owner;
 }

Robust.Shared/GameObjects/EntityExt.cs

@@ -1,104 +0,0 @@
-namespace Robust.Shared.GameObjects;
-
-public static class EntityExt
-{
-    /// <summary>
-    ///     Converts an Entity{T} to Entity{T?}, making it compatible with methods that take nullable components.
-    /// </summary>
-    /// <typeparam name="T">The component type. Must implement IComponent.</typeparam>
-    /// <param name="ent">The source entity to convert.</param>
-    /// <returns>An Entity{T?} with the same owner and component as the source entity.</returns>
-    /// <example>
-    ///     <code>
-    /// // Instead of:
-    /// Entity{MyComponent?} nullable = (ent, ent.Comp);
-    ///
-    /// // You can write:
-    /// Entity{MyComponent?} nullable = ent.AsNullable();
-    /// </code>
-    /// </example>
-    public static Entity<T?> AsNullable<T>(this Entity<T> ent) where T : IComponent
-    {
-        return new(ent.Owner, ent.Comp);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?> AsNullable<T1, T2>(this Entity<T1, T2> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?, T3?> AsNullable<T1, T2, T3>(this Entity<T1, T2, T3> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-        where T3 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2, ent.Comp3);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?, T3?, T4?> AsNullable<T1, T2, T3, T4>(this Entity<T1, T2, T3, T4> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-        where T3 : IComponent
-        where T4 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2, ent.Comp3, ent.Comp4);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?, T3?, T4?, T5?> AsNullable<T1, T2, T3, T4, T5>(this Entity<T1, T2, T3, T4, T5> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-        where T3 : IComponent
-        where T4 : IComponent
-        where T5 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2, ent.Comp3, ent.Comp4, ent.Comp5);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?, T3?, T4?, T5?, T6?> AsNullable<T1, T2, T3, T4, T5, T6>(
-        this Entity<T1, T2, T3, T4, T5, T6> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-        where T3 : IComponent
-        where T4 : IComponent
-        where T5 : IComponent
-        where T6 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2, ent.Comp3, ent.Comp4, ent.Comp5, ent.Comp6);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?, T3?, T4?, T5?, T6?, T7?> AsNullable<T1, T2, T3, T4, T5, T6, T7>(
-        this Entity<T1, T2, T3, T4, T5, T6, T7> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-        where T3 : IComponent
-        where T4 : IComponent
-        where T5 : IComponent
-        where T6 : IComponent
-        where T7 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2, ent.Comp3, ent.Comp4, ent.Comp5, ent.Comp6, ent.Comp7);
-    }
-
-    /// <inheritdoc cref="AsNullable{T}" />
-    public static Entity<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?> AsNullable<T1, T2, T3, T4, T5, T6, T7, T8>(
-        this Entity<T1, T2, T3, T4, T5, T6, T7, T8> ent)
-        where T1 : IComponent
-        where T2 : IComponent
-        where T3 : IComponent
-        where T4 : IComponent
-        where T5 : IComponent
-        where T6 : IComponent
-        where T7 : IComponent
-        where T8 : IComponent
-    {
-        return new(ent.Owner, ent.Comp1, ent.Comp2, ent.Comp3, ent.Comp4, ent.Comp5, ent.Comp6, ent.Comp7, ent.Comp8);
-    }
-}

Robust.Shared/GameObjects/EntityManager.Components.cs

@@ -595,12 +595,23 @@ namespace Robust.Shared.GameObjects
 
             if (!_deleteSet.Add(component))
             {
-                // already deferred deletion
+                // Already deferring deletion
+                DebugTools.Assert(component.LifeStage >= ComponentLifeStage.Stopped);
                 return;
             }
 
-            if (component.LifeStage >= ComponentLifeStage.Initialized && component.LifeStage <= ComponentLifeStage.Running)
+            DebugTools.Assert(component.LifeStage >= ComponentLifeStage.Added);
+
+            if (component.LifeStage is >= ComponentLifeStage.Initialized and < ComponentLifeStage.Stopping)
                 LifeShutdown(uid, component, _componentFactory.GetIndex(component.GetType()));
+            else if (component.LifeStage == ComponentLifeStage.Added)
+            {
+                // The component was added, but never initialized or started. It's kinda weird to add and then
+                // immediately defer-remove a component, but oh well. Let's just set the life stage directly and not
+                // raise shutdown events? The removal events will still get called later.
+                // This is also what LifeShutdown() would also do, albeit behind a DebugAssert.
+                component.LifeStage = ComponentLifeStage.Stopped;
+            }
 #if EXCEPTION_TOLERANCE
             }
             catch (Exception e)

Robust.Shared/GameObjects/EntityManager.LifeCycle.cs

@@ -14,8 +14,9 @@ public partial class EntityManager
     /// Increases the life stage from <see cref="ComponentLifeStage.PreAdd" /> to <see cref="ComponentLifeStage.Added" />,
     /// after raising a <see cref="ComponentAdd"/> event.
     /// </summary>
-    internal void LifeAddToEntity(EntityUid uid, IComponent component, CompIdx idx)
+    internal void LifeAddToEntity<T>(EntityUid uid, T component, CompIdx idx) where T : IComponent
     {
+        DebugTools.Assert(!_deleteSet.Contains(component));
         DebugTools.Assert(component.LifeStage == ComponentLifeStage.PreAdd);
 
 #pragma warning disable CS0618 // Type or member is obsolete
@@ -32,8 +33,9 @@ public partial class EntityManager
     /// Increases the life stage from <see cref="ComponentLifeStage.Added" /> to <see cref="ComponentLifeStage.Initialized" />,
     /// calling <see cref="Initialize" />.
     /// </summary>
-    internal void LifeInitialize(EntityUid uid, IComponent component, CompIdx idx)
+    internal void LifeInitialize<T>(EntityUid uid, T component, CompIdx idx) where T : IComponent
     {
+        DebugTools.Assert(!_deleteSet.Contains(component));
         DebugTools.Assert(component.LifeStage == ComponentLifeStage.Added);
 
         component.LifeStage = ComponentLifeStage.Initializing;
@@ -45,8 +47,9 @@ public partial class EntityManager
     /// Increases the life stage from <see cref="ComponentLifeStage.Initialized" /> to
     /// <see cref="ComponentLifeStage.Running" />, calling <see cref="Startup" />.
     /// </summary>
-    internal void LifeStartup(EntityUid uid, IComponent component, CompIdx idx)
+    internal void LifeStartup<T>(EntityUid uid, T component, CompIdx idx) where T : IComponent
     {
+        DebugTools.Assert(!_deleteSet.Contains(component));
         DebugTools.Assert(component.LifeStage == ComponentLifeStage.Initialized);
 
         component.LifeStage = ComponentLifeStage.Starting;
@@ -61,7 +64,7 @@ public partial class EntityManager
     /// <remarks>
     /// Components are allowed to remove themselves in their own Startup function.
     /// </remarks>
-    internal void LifeShutdown(EntityUid uid, IComponent component, CompIdx idx)
+    internal void LifeShutdown<T>(EntityUid uid, T component, CompIdx idx) where T : IComponent
     {
         DebugTools.Assert(component.LifeStage is >= ComponentLifeStage.Initializing and < ComponentLifeStage.Stopping);
 
@@ -81,7 +84,7 @@ public partial class EntityManager
     /// Increases the life stage from <see cref="ComponentLifeStage.Stopped" /> to <see cref="ComponentLifeStage.Deleted" />,
     /// calling <see cref="Component.OnRemove" />.
     /// </summary>
-    internal void LifeRemoveFromEntity(EntityUid uid, IComponent component, CompIdx idx)
+    internal void LifeRemoveFromEntity<T>(EntityUid uid, T component, CompIdx idx) where T : IComponent
     {
         // can be called at any time after PreAdd, including inside other life stage events.
         DebugTools.Assert(component.LifeStage != ComponentLifeStage.PreAdd);

Robust.Shared/GameObjects/EntityManager.Spawn.cs

@@ -6,6 +6,7 @@ using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using Robust.Shared.Containers;
 using Robust.Shared.Maths;
+using Robust.Shared.Serialization;
 
 namespace Robust.Shared.GameObjects;
 
@@ -79,7 +80,7 @@ public partial class EntityManager
             throw new InvalidOperationException($"Tried to spawn entity {protoName} on invalid coordinates {coordinates}.");
 
         var entity = CreateEntityUninitialized(protoName, coordinates, overrides, rotation);
-        InitializeAndStartEntity(entity, coordinates.GetMapId(this));
+        InitializeAndStartEntity(entity, _xforms.GetMapId(coordinates));
         return entity;
     }
 
@@ -100,7 +101,7 @@ public partial class EntityManager
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public EntityUid SpawnAtPosition(string? protoName, EntityCoordinates coordinates, ComponentRegistry? overrides = null)
-        => Spawn(protoName, coordinates.ToMap(this, _xforms), overrides);
+        => Spawn(protoName, _xforms.ToMapCoordinates(coordinates), overrides);
 
     public bool TrySpawnNextTo(
         string? protoName,
@@ -206,4 +207,91 @@ public partial class EntityManager
 
         return uid;
     }
+
+    #region Prediction
+
+    public virtual EntityUid PredictedSpawnAttachedTo(string? protoName, EntityCoordinates coordinates, ComponentRegistry? overrides = null, Angle rotation = default)
+    {
+        return SpawnAttachedTo(protoName, coordinates, overrides, rotation);
+    }
+
+    public virtual EntityUid PredictedSpawn(string? protoName = null, ComponentRegistry? overrides = null, bool doMapInit = true)
+    {
+        return Spawn(protoName, overrides, doMapInit);
+    }
+
+    public virtual EntityUid PredictedSpawn(string? protoName, MapCoordinates coordinates, ComponentRegistry? overrides = null, Angle rotation = default!)
+    {
+        return Spawn(protoName, coordinates, overrides, rotation);
+    }
+
+    public virtual EntityUid PredictedSpawnAtPosition(string? protoName, EntityCoordinates coordinates, ComponentRegistry? overrides = null)
+    {
+        return SpawnAtPosition(protoName, coordinates, overrides);
+    }
+
+    public virtual bool PredictedTrySpawnNextTo(
+        string? protoName,
+        EntityUid target,
+        [NotNullWhen(true)] out EntityUid? uid,
+        TransformComponent? xform = null,
+        ComponentRegistry? overrides = null)
+    {
+        return TrySpawnNextTo(protoName, target, out uid, xform, overrides);
+    }
+
+    public virtual bool PredictedTrySpawnInContainer(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        [NotNullWhen(true)] out EntityUid? uid,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        return TrySpawnInContainer(protoName, containerUid, containerId, out uid, containerComp, overrides);
+    }
+
+    public virtual EntityUid PredictedSpawnNextToOrDrop(string? protoName, EntityUid target, TransformComponent? xform = null, ComponentRegistry? overrides = null)
+    {
+        return SpawnNextToOrDrop(protoName, target, xform, overrides);
+    }
+
+    public virtual EntityUid PredictedSpawnInContainerOrDrop(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        TransformComponent? xform = null,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        return SpawnInContainerOrDrop(protoName, containerUid, containerId, xform, containerComp, overrides);
+    }
+
+    public virtual EntityUid PredictedSpawnInContainerOrDrop(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        out bool inserted,
+        TransformComponent? xform = null,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        return SpawnInContainerOrDrop(protoName,
+            containerUid,
+            containerId,
+            out inserted,
+            xform,
+            containerComp,
+            overrides);
+    }
+
+    /// <summary>
+    /// Flags an entity as being a predicted spawn and should be deleted when its corresponding tick comes in.
+    /// </summary>
+    public virtual void FlagPredicted(Entity<MetaDataComponent?> ent)
+    {
+
+    }
+
+    #endregion
 }

Robust.Shared/GameObjects/EntityManager.cs

@@ -48,7 +48,7 @@ namespace Robust.Shared.GameObjects
 
         // I feel like PJB might shed me for putting a system dependency here, but its required for setting entity
         // positions on spawn....
-        private SharedTransformSystem _xforms = default!;
+        protected SharedTransformSystem _xforms = default!;
         private SharedContainerSystem _containers = default!;
 
         public EntityQuery<MetaDataComponent> MetaQuery;
@@ -693,6 +693,36 @@ namespace Robust.Shared.GameObjects
 
         public bool IsQueuedForDeletion(EntityUid uid) => QueuedDeletionsSet.Contains(uid);
 
+        /// <inheritdoc />
+        public virtual void PredictedDeleteEntity(Entity<MetaDataComponent?, TransformComponent?> ent)
+        {
+            DeleteEntity(ent.Owner);
+        }
+
+        /// <inheritdoc />
+        public void PredictedDeleteEntity(Entity<MetaDataComponent?, TransformComponent?>? ent)
+        {
+            if (ent == null)
+                return;
+
+            PredictedDeleteEntity(ent.Value);
+        }
+
+        /// <inheritdoc />
+        public virtual void PredictedQueueDeleteEntity(Entity<MetaDataComponent?, TransformComponent?> ent)
+        {
+            QueueDeleteEntity(ent.Owner);
+        }
+
+        /// <inheritdoc />
+        public virtual void PredictedQueueDeleteEntity(Entity<MetaDataComponent?, TransformComponent?>? ent)
+        {
+            if (ent == null)
+                return;
+
+            PredictedQueueDeleteEntity(ent.Value);
+        }
+
         public bool EntityExists(EntityUid uid)
         {
             return MetaQuery.HasComponentInternal(uid);

Robust.Shared/GameObjects/EntitySystem.Proxy.cs

@@ -782,6 +782,34 @@ public partial class EntitySystem
         EntityManager.QueueDeleteEntity(uid);
     }
 
+    /// <inheritdoc cref="IEntityManager.DeleteEntity(EntityUid?)" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected void PredictedDel(Entity<MetaDataComponent?, TransformComponent?> ent)
+    {
+        EntityManager.PredictedDeleteEntity(ent);
+    }
+
+    /// <inheritdoc cref="IEntityManager.DeleteEntity(EntityUid?)" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected void PredictedDel(Entity<MetaDataComponent?, TransformComponent?>? ent)
+    {
+        EntityManager.PredictedDeleteEntity(ent);
+    }
+
+    /// <inheritdoc cref="IEntityManager.QueueDeleteEntity(EntityUid)" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected void PredictedQueueDel(Entity<MetaDataComponent?, TransformComponent?> ent)
+    {
+        EntityManager.PredictedQueueDeleteEntity(ent);
+    }
+
+    /// <inheritdoc cref="IEntityManager.QueueDeleteEntity(EntityUid?)" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected void PredictedQueueDel(Entity<MetaDataComponent?, TransformComponent?>? ent)
+    {
+        EntityManager.PredictedQueueDeleteEntity(ent);
+    }
+
     /// <inheritdoc cref="IEntityManager.TryQueueDeleteEntity(EntityUid?)" />
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     protected bool TryQueueDel(EntityUid? uid)
@@ -812,8 +840,8 @@ public partial class EntitySystem
 
     /// <inheritdoc cref="IEntityManager.SpawnAttachedTo" />
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    protected EntityUid SpawnAttachedTo(string? prototype, EntityCoordinates coordinates, ComponentRegistry? overrides = null)
-        => EntityManager.SpawnAttachedTo(prototype, coordinates, overrides);
+    protected EntityUid SpawnAttachedTo(string? prototype, EntityCoordinates coordinates, ComponentRegistry? overrides = null, Angle rotation = default)
+        => EntityManager.SpawnAttachedTo(prototype, coordinates, overrides, rotation);
 
     /// <inheritdoc cref="IEntityManager.SpawnAtPosition" />
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -871,6 +899,74 @@ public partial class EntitySystem
 
     #endregion
 
+    #region PredictedSpawning
+
+    protected void FlagPredicted(Entity<MetaDataComponent?> ent)
+    {
+        EntityManager.FlagPredicted(ent);
+    }
+
+    /// <inheritdoc cref="IEntityManager.SpawnAttachedTo" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected EntityUid PredictedSpawnAttachedTo(string? prototype, EntityCoordinates coordinates, ComponentRegistry? overrides = null, Angle rotation = default)
+        => EntityManager.PredictedSpawnAttachedTo(prototype, coordinates, overrides, rotation);
+
+    /// <inheritdoc cref="IEntityManager.SpawnAtPosition" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected EntityUid PredictedSpawnAtPosition(string? prototype, EntityCoordinates coordinates, ComponentRegistry? overrides = null)
+        => EntityManager.PredictedSpawnAtPosition(prototype, coordinates, overrides);
+
+    /// <inheritdoc cref="IEntityManager.TrySpawnInContainer" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected bool PredictedTrySpawnInContainer(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        [NotNullWhen(true)] out EntityUid? uid,
+        ContainerManagerComponent? containerComp = null,
+        ComponentRegistry? overrides = null)
+    {
+        return EntityManager.PredictedTrySpawnInContainer(protoName, containerUid, containerId, out uid, containerComp, overrides);
+    }
+
+    /// <inheritdoc cref="IEntityManager.TrySpawnNextTo" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected bool PredictedTrySpawnNextTo(
+        string? protoName,
+        EntityUid target,
+        [NotNullWhen(true)] out EntityUid? uid,
+        TransformComponent? xform = null,
+        ComponentRegistry? overrides = null)
+    {
+        return EntityManager.PredictedTrySpawnNextTo(protoName, target, out uid, xform, overrides);
+    }
+
+    /// <inheritdoc cref="IEntityManager.SpawnNextToOrDrop" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected EntityUid PredictedSpawnNextToOrDrop(
+        string? protoName,
+        EntityUid target,
+        TransformComponent? xform = null,
+        ComponentRegistry? overrides = null)
+    {
+        return EntityManager.PredictedSpawnNextToOrDrop(protoName, target, xform, overrides);
+    }
+
+    /// <inheritdoc cref="IEntityManager.SpawnInContainerOrDrop" />
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected EntityUid PredictedSpawnInContainerOrDrop(
+        string? protoName,
+        EntityUid containerUid,
+        string containerId,
+        TransformComponent? xform = null,
+        ContainerManagerComponent? container = null,
+        ComponentRegistry? overrides = null)
+    {
+        return EntityManager.PredictedSpawnInContainerOrDrop(protoName, containerUid, containerId, xform, container, overrides);
+    }
+
+    #endregion
+
     #region Utils
 
     /// <summary>

Robust.Shared/GameObjects/EntitySystem.Resolve.cs

@@ -37,18 +37,22 @@ namespace Robust.Shared.GameObjects
 
         /// <inheritdoc cref="Resolve{TComp}(Robust.Shared.GameObjects.EntityUid,ref TComp?,bool)"/>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        protected bool Resolve(EntityUid uid, [NotNullWhen(true)] ref MetaDataComponent? component,
+        protected bool Resolve(
+            EntityUid uid,
+            [NotNullWhen(true)] ref MetaDataComponent? component,
             bool logMissing = true)
         {
-            return EntityManager.MetaQuery.Resolve(uid, ref component);
+            return EntityManager.MetaQuery.Resolve(uid, ref component, logMissing);
         }
 
         /// <inheritdoc cref="Resolve{TComp}(Robust.Shared.GameObjects.EntityUid,ref TComp?,bool)"/>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        protected bool Resolve(EntityUid uid, [NotNullWhen(true)] ref TransformComponent? component,
+        protected bool Resolve(
+            EntityUid uid,
+            [NotNullWhen(true)] ref TransformComponent? component,
             bool logMissing = true)
         {
-            return EntityManager.TransformQuery.Resolve(uid, ref component);
+            return EntityManager.TransformQuery.Resolve(uid, ref component, logMissing);
         }
 
         /// <summary>