refactor(runtime): acknowledge exact world host projections

src/AcDream.App/Composition/FrameRootComposition.cs

@@ -453,6 +453,8 @@ internal sealed class FrameRootCompositionPhase
             lifecycleAutomation =
                 new WorldLifecycleAutomationController(
                     () => session.WorldReveal.Snapshot,
+                    () => d.WorldEnvironment.Runtime.Ownership,
+                    () => live.WorldTransit.Ownership,
                     () => session.WorldReveal.PortalMaterializationCount,
                     resourceSnapshots.Capture,
                     screenshots,

src/AcDream.App/Diagnostics/WorldLifecycleAutomationController.cs

@@ -6,6 +6,7 @@ using AcDream.App.Streaming;
 using AcDream.App.UI.Testing;
 using AcDream.Core.Physics;
 using AcDream.Runtime;
+using AcDream.Runtime.World;
 
 namespace AcDream.App.Diagnostics;
 
@@ -103,6 +104,8 @@ internal sealed record WorldLifecycleCheckpoint(
     DateTime TimestampUtc,
     int ProcessId,
     RuntimePortalSnapshot Reveal,
+    RuntimeWorldEnvironmentOwnershipSnapshot EnvironmentOwnership,
+    RuntimeWorldTransitOwnershipSnapshot TransitOwnership,
     RenderFrameOutcome Render,
     WorldLifecycleResourceSnapshot Resources);
 
@@ -177,6 +180,10 @@ internal sealed class WorldLifecycleAutomationController :
     };
 
     private readonly Func<RuntimePortalSnapshot> _getReveal;
+    private readonly Func<RuntimeWorldEnvironmentOwnershipSnapshot>
+        _getEnvironmentOwnership;
+    private readonly Func<RuntimeWorldTransitOwnershipSnapshot>
+        _getTransitOwnership;
     private readonly Func<int> _getPortalMaterializationCount;
     private readonly Func<RenderFrameOutcome, WorldLifecycleResourceSnapshot>
         _captureResources;
@@ -191,6 +198,9 @@ internal sealed class WorldLifecycleAutomationController :
 
     public WorldLifecycleAutomationController(
         Func<RuntimePortalSnapshot> getReveal,
+        Func<RuntimeWorldEnvironmentOwnershipSnapshot>
+            getEnvironmentOwnership,
+        Func<RuntimeWorldTransitOwnershipSnapshot> getTransitOwnership,
         Func<int> getPortalMaterializationCount,
         Func<RenderFrameOutcome, WorldLifecycleResourceSnapshot> captureResources,
         FrameScreenshotController screenshots,
@@ -198,6 +208,11 @@ internal sealed class WorldLifecycleAutomationController :
         Action<string>? log = null)
     {
         _getReveal = getReveal ?? throw new ArgumentNullException(nameof(getReveal));
+        _getEnvironmentOwnership = getEnvironmentOwnership
+            ?? throw new ArgumentNullException(
+                nameof(getEnvironmentOwnership));
+        _getTransitOwnership = getTransitOwnership
+            ?? throw new ArgumentNullException(nameof(getTransitOwnership));
         _getPortalMaterializationCount = getPortalMaterializationCount
             ?? throw new ArgumentNullException(nameof(getPortalMaterializationCount));
         _captureResources = captureResources ?? throw new ArgumentNullException(nameof(captureResources));
@@ -289,6 +304,8 @@ internal sealed class WorldLifecycleAutomationController :
                 TimestampUtc: DateTime.UtcNow,
                 ProcessId: Environment.ProcessId,
                 Reveal: _getReveal(),
+                EnvironmentOwnership: _getEnvironmentOwnership(),
+                TransitOwnership: _getTransitOwnership(),
                 Render: outcome,
                 Resources: _captureResources(outcome));
             string json = JsonSerializer.Serialize(checkpoint, JsonOptions);

src/AcDream.App/Runtime/CurrentGameRuntimeViewAdapter.cs

@@ -126,7 +126,9 @@ internal sealed class CurrentGameRuntimeViewAdapter : IGameRuntimeView
             _actionView.Snapshot,
             _movementView.Snapshot,
             _environmentView.Snapshot,
-            _portalView.Snapshot);
+            _environmentView.Ownership,
+            _portalView.Snapshot,
+            _portalView.Ownership);
 
     internal void Deactivate() => _active = false;
 }

src/AcDream.App/Streaming/WorldGenerationQuiescence.cs

@@ -63,6 +63,9 @@ internal sealed class WorldGenerationQuiescence
     private readonly Func<uint, RuntimeEntityKey?> _resolveProjectionKey;
     private readonly IWorldAudioQuiescence? _audio;
     private bool _effectsQuiesced;
+    private bool _selectionEdgeCommitted;
+    private bool _audioSuspended;
+    private bool _audioTransitionActive;
 
     public WorldGenerationQuiescence(
         SelectionState selection,
@@ -99,26 +102,62 @@ internal sealed class WorldGenerationQuiescence
 
     public void CommitBegin(in WorldGenerationQuiescenceEdge edge)
     {
-        if (!edge.ShouldApply || _effectsQuiesced)
+        if (!edge.ShouldApply)
             return;
 
         _effectsQuiesced = true;
+        if (!_selectionEdgeCommitted)
+        {
+            // SelectionState commits its value before notifying observers.
+            // Record the edge first so a re-entrant reveal cannot replay it.
+            _selectionEdgeCommitted = true;
             if (edge.ClearWorldSelection)
             {
                 _selection.Clear(
                     SelectionChangeSource.System,
                     SelectionChangeReason.Cleared);
             }
+        }
 
-        _audio?.SuspendWorldAudio();
+        ReconcileAudio();
     }
 
     public void ObserveReleased()
     {
-        if (!_effectsQuiesced)
+        if (!_effectsQuiesced
+            && !_selectionEdgeCommitted
+            && !_audioSuspended)
+        {
             return;
+        }
 
         _effectsQuiesced = false;
-        _audio?.ResumeWorldAudio();
+        ReconcileAudio();
+        if (!_effectsQuiesced && !_audioSuspended)
+            _selectionEdgeCommitted = false;
+    }
+
+    private void ReconcileAudio()
+    {
+        if (_audio is null || _audioTransitionActive)
+            return;
+
+        _audioTransitionActive = true;
+        try
+        {
+            while (_audioSuspended != _effectsQuiesced)
+            {
+                bool suspend = _effectsQuiesced;
+                if (suspend)
+                    _audio.SuspendWorldAudio();
+                else
+                    _audio.ResumeWorldAudio();
+                _audioSuspended = suspend;
+            }
+        }
+        finally
+        {
+            _audioTransitionActive = false;
+        }
     }
 }

src/AcDream.App/Streaming/WorldRevealCoordinator.cs

@@ -37,13 +37,31 @@ internal interface IWorldRevealRenderResourceScheduler
 /// </summary>
 internal sealed class WorldRevealCoordinator
 {
+    private sealed class HostProjection(
+        RuntimeWorldHostProjectionToken token,
+        int requiredRenderRadius,
+        in WorldGenerationQuiescenceEdge quiescenceEdge)
+    {
+        public RuntimeWorldHostProjectionToken Token { get; } = token;
+        public int RequiredRenderRadius { get; } = requiredRenderRadius;
+        public WorldGenerationQuiescenceEdge QuiescenceEdge { get; } =
+            quiescenceEdge;
+        public bool QuiescenceCommitted { get; set; }
+        public bool StreamingRegistered { get; set; }
+        public bool RenderResourcesRegistered { get; set; }
+        public bool SimulationReleaseProjected { get; set; }
+        public bool StreamingReleased { get; set; }
+        public bool RenderResourcesReleased { get; set; }
+    }
+
     private readonly RuntimeWorldTransitState _transit;
     private readonly WorldRevealReadinessBarrier _readiness;
     private readonly WorldGenerationQuiescence? _quiescence;
     private readonly IWorldRevealStreamingScheduler? _streaming;
     private readonly IWorldRevealRenderResourceScheduler? _renderResources;
-    private long _reservationGeneration;
-    private bool _worldViewportReleased;
+    private readonly List<HostProjection> _hostProjections = [];
+    private bool _hostRetryActive;
+    private bool _hostRetryRequested;
 
     public WorldRevealCoordinator(
         RuntimeWorldTransitState transit,
@@ -76,12 +94,15 @@ internal sealed class WorldRevealCoordinator
     public int PortalMaterializationCount =>
         _transit.Snapshot.PortalMaterializationCount;
     public bool WaitCueShown => _transit.Snapshot.WaitCueShown;
+    public RuntimeWorldTransitOwnershipSnapshot Ownership =>
+        _transit.Ownership;
 
     public long BeginLogin(uint destinationCell)
     {
         if (destinationCell == 0u)
             throw new ArgumentOutOfRangeException(nameof(destinationCell));
 
+        WithdrawHostForReplacement();
         WorldGenerationQuiescenceEdge quiescenceEdge =
             _quiescence?.CaptureBegin() ?? default;
         _readiness.Begin();
@@ -100,7 +121,15 @@ internal sealed class WorldRevealCoordinator
     {
         if (destinationCell == 0u)
             throw new ArgumentOutOfRangeException(nameof(destinationCell));
+        if (!_transit.CanBeginPortalReveal(
+                teleportSequence,
+                destinationCell))
+        {
+            generation = 0;
+            return false;
+        }
 
+        WithdrawHostForReplacement();
         WorldGenerationQuiescenceEdge quiescenceEdge =
             _quiescence?.CaptureBegin() ?? default;
         if (!_transit.TryBeginPortalReveal(
@@ -124,14 +153,21 @@ internal sealed class WorldRevealCoordinator
         uint destinationCell,
         in WorldGenerationQuiescenceEdge quiescenceEdge)
     {
-        _quiescence?.CommitBegin(quiescenceEdge);
-        _reservationGeneration = generation;
-        _worldViewportReleased = false;
-        _streaming?.BeginDestinationReservation(
+        if (!_transit.TryRegisterHostProjection(
                 generation,
                 destinationCell,
-            WorldRevealReadinessBarrier.RequiredRenderRadius(destinationCell));
-        _renderResources?.BeginDestinationReveal(generation);
+                out RuntimeWorldHostProjectionToken token))
+        {
+            throw new InvalidOperationException(
+                "Runtime rejected the exact reveal host projection.");
+        }
+
+        _hostProjections.Add(new HostProjection(
+            token,
+            WorldRevealReadinessBarrier.RequiredRenderRadius(
+                destinationCell),
+            quiescenceEdge));
+        RetryPendingHostWork();
     }
 
     /// <summary>
@@ -146,6 +182,7 @@ internal sealed class WorldRevealCoordinator
 
     public WorldRevealReadinessSnapshot Evaluate(uint destinationCell)
     {
+        RetryPendingHostWork();
         WorldRevealReadinessSnapshot snapshot = _readiness.Evaluate(destinationCell);
         RuntimePortalSnapshot portal = _transit.Snapshot;
         if (portal.Generation != 0)
@@ -189,17 +226,17 @@ internal sealed class WorldRevealCoordinator
         ushort teleportSequence,
         uint destinationCell)
     {
-        bool wasAvailable = _transit.IsWorldSimulationAvailable;
         bool acknowledged = _transit.AcknowledgePortalMaterialized(
             generation,
             teleportSequence,
             destinationCell);
-        ObserveSimulationRelease(wasAvailable);
+        RetryPendingHostWork();
         return acknowledged;
     }
 
     public void ObserveWorldViewportVisible()
     {
+        RetryPendingHostWork();
         long generation = _transit.Snapshot.Generation;
         if (generation != 0)
             _transit.AcknowledgeWorldViewportVisible(generation);
@@ -220,13 +257,12 @@ internal sealed class WorldRevealCoordinator
     /// </summary>
     public void RevealWorldViewport()
     {
-        long generation = _reservationGeneration;
-        if (generation == 0 || _worldViewportReleased)
+        HostProjection? host = FindCurrentHostProjection();
+        if (host is null)
             return;
 
-        _streaming?.EndDestinationReservation(generation);
-        _renderResources?.EndDestinationReveal(generation);
-        _worldViewportReleased = true;
+        _transit.RequireDestinationReservationRelease(host.Token);
+        RetryPendingHostWork();
     }
 
     public void Complete()
@@ -235,10 +271,8 @@ internal sealed class WorldRevealCoordinator
         if (generation == 0)
             return;
 
-        bool wasAvailable = _transit.IsWorldSimulationAvailable;
         _transit.Complete(generation);
-        ObserveSimulationRelease(wasAvailable);
-        EndHostLifetime();
+        RetryPendingHostWork();
     }
 
     public void Cancel()
@@ -247,37 +281,284 @@ internal sealed class WorldRevealCoordinator
         if (generation == 0)
             return;
 
-        bool wasAvailable = _transit.IsWorldSimulationAvailable;
         _transit.Cancel(generation);
-        ObserveSimulationRelease(wasAvailable);
-        EndHostLifetime();
+        RetryPendingHostWork();
     }
 
     public void ResetSession()
     {
-        bool wasAvailable = _transit.IsWorldSimulationAvailable;
         long generation = _transit.Snapshot.Generation;
         if (generation != 0)
             _transit.Cancel(generation);
-        ObserveSimulationRelease(wasAvailable);
-        EndHostLifetime();
+        RetryPendingHostWork();
         _transit.ResetSession();
     }
 
-    private void EndHostLifetime()
+    /// <summary>
+    /// Resumes the exact unfinished graphical-host suffix. Completed callback
+    /// stages never replay; a thrown callback leaves its Runtime
+    /// acknowledgement pending for the next call.
+    /// </summary>
+    internal void RetryPendingHostWork()
     {
-        long generation = _reservationGeneration;
-        if (generation == 0)
+        _hostRetryRequested = true;
+        if (_hostRetryActive)
             return;
 
-        RevealWorldViewport();
-        _reservationGeneration = 0;
-        _worldViewportReleased = false;
+        _hostRetryActive = true;
+        try
+        {
+            do
+            {
+                _hostRetryRequested = false;
+                int index = 0;
+                while (index < _hostProjections.Count)
+                {
+                    HostProjection host = _hostProjections[index];
+                    DrainHostProjection(host);
+                    if (index < _hostProjections.Count
+                        && ReferenceEquals(
+                            _hostProjections[index],
+                            host))
+                    {
+                        index++;
+                    }
+                }
+            }
+            while (_hostRetryRequested);
+        }
+        finally
+        {
+            _hostRetryActive = false;
+        }
     }
 
-    private void ObserveSimulationRelease(bool wasAvailable)
+    private void DrainHostProjection(HostProjection host)
+    {
+        if (!TryGetHostProjection(host, out var projection))
+            return;
+
+        RuntimeWorldHostAcknowledgementStage pending =
+            projection.PendingAcknowledgements;
+        if ((pending & RuntimeWorldHostAcknowledgementStage
+                .ProjectionRegistered) != 0)
+        {
+            CompleteHostRegistration(host);
+        }
+
+        if (!TryGetHostProjection(host, out projection))
+            return;
+        pending = projection.PendingAcknowledgements;
+        if ((pending & RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected) != 0)
+        {
+            CompleteSimulationRelease(host);
+        }
+
+        if (!TryGetHostProjection(host, out projection))
+            return;
+        pending = projection.PendingAcknowledgements;
+        if ((pending & RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased) != 0)
+        {
+            CompleteDestinationReservationRelease(host);
+        }
+
+        if (!TryGetHostProjection(host, out projection))
+            return;
+        if ((projection.PendingAcknowledgements
+                & RuntimeWorldHostAcknowledgementStage.TerminalProjected)
+            == 0)
+        {
+            return;
+        }
+
+        Acknowledge(
+            host,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected);
+        RemoveHostProjection(host);
+    }
+
+    private void CompleteHostRegistration(HostProjection host)
+    {
+        if (!host.QuiescenceCommitted)
+        {
+            _quiescence?.CommitBegin(host.QuiescenceEdge);
+            host.QuiescenceCommitted = true;
+        }
+        if (!IsStagePending(
+                host,
+                RuntimeWorldHostAcknowledgementStage
+                    .ProjectionRegistered))
+        {
+            return;
+        }
+        if (!host.StreamingRegistered)
+        {
+            _streaming?.BeginDestinationReservation(
+                host.Token.Generation,
+                host.Token.DestinationCell,
+                host.RequiredRenderRadius);
+            host.StreamingRegistered = true;
+        }
+        if (!IsStagePending(
+                host,
+                RuntimeWorldHostAcknowledgementStage
+                    .ProjectionRegistered))
+        {
+            return;
+        }
+        if (!host.RenderResourcesRegistered)
+        {
+            _renderResources?.BeginDestinationReveal(
+                host.Token.Generation);
+            host.RenderResourcesRegistered = true;
+        }
+        if (!IsStagePending(
+                host,
+                RuntimeWorldHostAcknowledgementStage
+                    .ProjectionRegistered))
+        {
+            return;
+        }
+
+        Acknowledge(
+            host,
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered);
+    }
+
+    private void CompleteSimulationRelease(HostProjection host)
+    {
+        if (!host.SimulationReleaseProjected)
         {
-        if (!wasAvailable && _transit.IsWorldSimulationAvailable)
             _quiescence?.ObserveReleased();
+            host.SimulationReleaseProjected = true;
+        }
+        if (!IsStagePending(
+                host,
+                RuntimeWorldHostAcknowledgementStage
+                    .SimulationReleaseProjected))
+        {
+            return;
+        }
+
+        Acknowledge(
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected);
+    }
+
+    private void CompleteDestinationReservationRelease(HostProjection host)
+    {
+        if (!host.StreamingReleased)
+        {
+            if (host.StreamingRegistered)
+            {
+                _streaming?.EndDestinationReservation(
+                    host.Token.Generation);
+            }
+            host.StreamingReleased = true;
+        }
+        if (!IsStagePending(
+                host,
+                RuntimeWorldHostAcknowledgementStage
+                    .DestinationReservationReleased))
+        {
+            return;
+        }
+        if (!host.RenderResourcesReleased)
+        {
+            if (host.RenderResourcesRegistered)
+            {
+                _renderResources?.EndDestinationReveal(
+                    host.Token.Generation);
+            }
+            host.RenderResourcesReleased = true;
+        }
+        if (!IsStagePending(
+                host,
+                RuntimeWorldHostAcknowledgementStage
+                    .DestinationReservationReleased))
+        {
+            return;
+        }
+
+        Acknowledge(
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased);
+    }
+
+    private void WithdrawHostForReplacement()
+    {
+        HostProjection? host = FindCurrentHostProjection();
+        if (host is null)
+            return;
+
+        if (!_transit.BeginHostProjectionSupersession(host.Token))
+        {
+            throw new InvalidOperationException(
+                "Runtime rejected reveal-host supersession.");
+        }
+        RetryPendingHostWork();
+    }
+
+    private HostProjection? FindCurrentHostProjection()
+    {
+        long generation = _transit.Snapshot.Generation;
+        for (int i = 0; i < _hostProjections.Count; i++)
+        {
+            HostProjection candidate = _hostProjections[i];
+            if (candidate.Token.Generation == generation)
+                return candidate;
+        }
+
+        return null;
+    }
+
+    private bool TryGetHostProjection(
+        HostProjection host,
+        out RuntimeWorldHostProjectionSnapshot projection)
+    {
+        if (_transit.TryGetHostProjection(host.Token, out projection))
+            return true;
+
+        RemoveHostProjection(host);
+        return false;
+    }
+
+    private bool IsStagePending(
+        HostProjection host,
+        RuntimeWorldHostAcknowledgementStage stage) =>
+        _transit.TryGetHostProjection(
+            host.Token,
+            out RuntimeWorldHostProjectionSnapshot projection)
+        && (projection.PendingAcknowledgements & stage) != 0;
+
+    private void RemoveHostProjection(HostProjection host)
+    {
+        for (int i = 0; i < _hostProjections.Count; i++)
+        {
+            if (!ReferenceEquals(_hostProjections[i], host))
+                continue;
+
+            _hostProjections.RemoveAt(i);
+            return;
+        }
+    }
+
+    private void Acknowledge(
+        HostProjection host,
+        RuntimeWorldHostAcknowledgementStage stage)
+    {
+        if (!_transit.AcknowledgeHostProjection(
+                new RuntimeWorldHostAcknowledgement(
+                    host.Token,
+                    stage)))
+        {
+            throw new InvalidOperationException(
+                $"Runtime rejected reveal host acknowledgement {stage} "
+                + $"for generation {host.Token.Generation}.");
+        }
     }
 }

src/AcDream.Runtime/GameRuntimeEvents.cs

@@ -192,8 +192,19 @@ public sealed class RuntimeTraceRecorder : IRuntimeEventObserver
                 $"{checkpoint.Environment.ActiveDayGroupIndex}:" +
                 $"{(int)checkpoint.Environment.Weather}:" +
                 $"{(int)checkpoint.Environment.EnvironOverride};" +
+                $"environment-owner={checkpoint.EnvironmentOwnership.IsInitialized}:" +
+                $"{checkpoint.EnvironmentOwnership.DayGroupDefinitionCount}:" +
+                $"{checkpoint.EnvironmentOwnership.ActiveDayGroupCount};" +
                 $"portal={checkpoint.Portal.Generation}:{(int)checkpoint.Portal.Kind}:" +
-                $"{checkpoint.Portal.DestinationCell:X8}:{checkpoint.Portal.IsReady}")));
+                $"{checkpoint.Portal.DestinationCell:X8}:{checkpoint.Portal.IsReady};" +
+                $"transit-owner={checkpoint.TransitOwnership.BufferedTeleportDestinationCount}:" +
+                $"{checkpoint.TransitOwnership.PendingTeleportStartCount}:" +
+                $"{checkpoint.TransitOwnership.ActiveTeleportCount}:" +
+                $"{checkpoint.TransitOwnership.AcceptedTeleportDestinationCount}:" +
+                $"{checkpoint.TransitOwnership.ActiveRevealCount}:" +
+                $"{checkpoint.TransitOwnership.PendingDestinationReadinessCount}:" +
+                $"{checkpoint.TransitOwnership.HostProjectionCount}:" +
+                $"{checkpoint.TransitOwnership.PendingHostAcknowledgementCount}")));
     }
 
     public void OnLifecycle(in RuntimeLifecycleDelta delta) =>

src/AcDream.Runtime/GameRuntimeViews.cs

@@ -128,6 +128,55 @@ public readonly record struct RuntimeDestinationReadiness(
                 && IsCollisionReady));
 }
 
+[Flags]
+public enum RuntimeWorldHostAcknowledgementStage
+{
+    None = 0,
+    ProjectionRegistered = 1 << 0,
+    SimulationReleaseProjected = 1 << 1,
+    DestinationReservationReleased = 1 << 2,
+    TerminalProjected = 1 << 3,
+}
+
+/// <summary>
+/// Exact identity of one graphical or direct host projection attached to a
+/// Runtime reveal generation. It contains no presentation object.
+/// </summary>
+public readonly record struct RuntimeWorldHostProjectionToken(
+    long Generation,
+    uint DestinationCell)
+{
+    public bool IsValid => Generation != 0 && DestinationCell != 0u;
+}
+
+public readonly record struct RuntimeWorldHostAcknowledgement(
+    RuntimeWorldHostProjectionToken Projection,
+    RuntimeWorldHostAcknowledgementStage Stage);
+
+public readonly record struct RuntimeWorldHostProjectionSnapshot(
+    RuntimeWorldHostProjectionToken Token,
+    RuntimeWorldHostAcknowledgementStage PendingAcknowledgements,
+    bool ProjectionRegistered,
+    bool SimulationReleaseProjected,
+    bool DestinationReservationReleased,
+    bool IsSuperseding)
+{
+    public int PendingAcknowledgementCount =>
+        Count(PendingAcknowledgements);
+
+    private static int Count(RuntimeWorldHostAcknowledgementStage stages)
+    {
+        int value = (int)stages;
+        int count = 0;
+        while (value != 0)
+        {
+            value &= value - 1;
+            count++;
+        }
+        return count;
+    }
+}
+
 public readonly record struct RuntimePortalSnapshot(
     long Generation,
     RuntimePortalKind Kind,
@@ -166,6 +215,7 @@ public readonly record struct RuntimePortalSnapshot(
 public interface IRuntimePortalView
 {
     RuntimePortalSnapshot Snapshot { get; }
+    RuntimeWorldTransitOwnershipSnapshot Ownership { get; }
 }
 
 public readonly record struct RuntimeStateCheckpoint(
@@ -184,7 +234,9 @@ public readonly record struct RuntimeStateCheckpoint(
     RuntimeActionSnapshot Actions,
     RuntimeMovementSnapshot Movement,
     RuntimeWorldEnvironmentSnapshot Environment,
-    RuntimePortalSnapshot Portal);
+    RuntimeWorldEnvironmentOwnershipSnapshot EnvironmentOwnership,
+    RuntimePortalSnapshot Portal,
+    RuntimeWorldTransitOwnershipSnapshot TransitOwnership);
 
 public interface IGameRuntimeView
 {

src/AcDream.Runtime/World/RuntimeWorldEnvironmentState.cs

@@ -96,9 +96,15 @@ public readonly record struct RuntimeWorldEnvironmentSnapshot(
     WeatherKind Weather,
     EnvironOverride EnvironOverride);
 
+public readonly record struct RuntimeWorldEnvironmentOwnershipSnapshot(
+    bool IsInitialized,
+    int DayGroupDefinitionCount,
+    int ActiveDayGroupCount);
+
 public interface IRuntimeWorldEnvironmentView
 {
     RuntimeWorldEnvironmentSnapshot Snapshot { get; }
+    RuntimeWorldEnvironmentOwnershipSnapshot Ownership { get; }
 }
 
 /// <summary>
@@ -152,6 +158,15 @@ public sealed class RuntimeWorldEnvironmentState
         Weather.Kind,
         Weather.Override);
 
+    public RuntimeWorldEnvironmentOwnershipSnapshot Ownership =>
+        CaptureOwnership();
+
+    public RuntimeWorldEnvironmentOwnershipSnapshot CaptureOwnership() =>
+        new(
+            IsInitialized,
+            _definition?.DayGroups.Count ?? 0,
+            ActiveDayGroupIndex >= 0 ? 1 : 0);
+
     public void Initialize(RuntimeWorldEnvironmentDefinition definition)
     {
         ArgumentNullException.ThrowIfNull(definition);

src/AcDream.Runtime/World/RuntimeWorldTransitState.cs

@@ -2,6 +2,27 @@ using System.Globalization;
 
 namespace AcDream.Runtime.World;
 
+public readonly record struct RuntimeWorldTransitOwnershipSnapshot(
+    int BufferedTeleportDestinationCount,
+    int PendingTeleportStartCount,
+    int ActiveTeleportCount,
+    int AcceptedTeleportDestinationCount,
+    int ActiveRevealCount,
+    int PendingDestinationReadinessCount,
+    int HostProjectionCount,
+    int PendingHostAcknowledgementCount)
+{
+    public bool IsSessionIdle =>
+        BufferedTeleportDestinationCount == 0
+        && PendingTeleportStartCount == 0
+        && ActiveTeleportCount == 0
+        && AcceptedTeleportDestinationCount == 0
+        && ActiveRevealCount == 0
+        && PendingDestinationReadinessCount == 0
+        && HostProjectionCount == 0
+        && PendingHostAcknowledgementCount == 0;
+}
+
 /// <summary>
 /// Canonical presentation-independent owner of local F751/Position
 /// correlation and one login/portal reveal generation. The graphical or
@@ -21,12 +42,34 @@ namespace AcDream.Runtime.World;
 public sealed class RuntimeWorldTransitState
     : IRuntimePortalView
 {
+    private sealed class HostProjectionRecord(
+        RuntimeWorldHostProjectionToken token)
+    {
+        public RuntimeWorldHostProjectionToken Token { get; } = token;
+        public RuntimeWorldHostAcknowledgementStage Pending { get; set; } =
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered;
+        public bool ProjectionRegistered { get; set; }
+        public bool SimulationReleaseProjected { get; set; }
+        public bool DestinationReservationReleased { get; set; }
+        public bool IsSuperseding { get; set; }
+
+        public RuntimeWorldHostProjectionSnapshot Snapshot => new(
+            Token,
+            Pending,
+            ProjectionRegistered,
+            SimulationReleaseProjected,
+            DestinationReservationReleased,
+            IsSuperseding);
+    }
+
     public static readonly TimeSpan RetailWaitCueDelay =
         TimeSpan.FromSeconds(5);
 
     private readonly Action<string> _log;
     private readonly Dictionary<ushort, RuntimeTeleportDestination>
         _bufferedDestinations = [];
+    private readonly Dictionary<long, HostProjectionRecord>
+        _hostProjections = [];
     private RuntimePortalSnapshot _snapshot = RuntimePortalSnapshot.Idle;
     private long _nextGeneration;
     private bool _hasLastTeleportStart;
@@ -45,6 +88,8 @@ public sealed class RuntimeWorldTransitState
     }
 
     public RuntimePortalSnapshot Snapshot => _snapshot;
+    public RuntimeWorldTransitOwnershipSnapshot Ownership =>
+        CaptureOwnership();
     public bool IsWorldSimulationAvailable =>
         _snapshot.WorldSimulationAvailable;
     public bool IsTeleportActive => _teleportActive;
@@ -57,6 +102,30 @@ public sealed class RuntimeWorldTransitState
     public int DiagnosticFailureCount { get; private set; }
     public Exception? LastDiagnosticFailure { get; private set; }
 
+    public RuntimeWorldTransitOwnershipSnapshot CaptureOwnership()
+    {
+        int pendingHostAcknowledgements = 0;
+        foreach (HostProjectionRecord host in _hostProjections.Values)
+        {
+            pendingHostAcknowledgements = checked(
+                pendingHostAcknowledgements
+                + host.Snapshot.PendingAcknowledgementCount);
+        }
+
+        bool revealActive = _snapshot.Generation != 0
+            && !_snapshot.Completed
+            && !_snapshot.Cancelled;
+        return new RuntimeWorldTransitOwnershipSnapshot(
+            _bufferedDestinations.Count,
+            _hasPendingTeleportStart ? 1 : 0,
+            _teleportActive ? 1 : 0,
+            _hasAcceptedDestination ? 1 : 0,
+            revealActive ? 1 : 0,
+            revealActive && !_snapshot.IsReady ? 1 : 0,
+            _hostProjections.Count,
+            pendingHostAcknowledgements);
+    }
+
     /// <summary>
     /// Starts initial-login reveal. Portal reveals must instead claim the
     /// exact F751-correlated destination through
@@ -69,15 +138,30 @@ public sealed class RuntimeWorldTransitState
     /// Atomically claims the one accepted Position paired with the active F751
     /// sequence and starts its reveal generation.
     /// </summary>
+    public bool CanBeginPortalReveal(
+        ushort teleportSequence,
+        uint destinationCell)
+    {
+        if (!_teleportActive
+            || teleportSequence != _activeTeleportSequence
+            || !_hasAcceptedDestination)
+        {
+            return false;
+        }
+
+        RuntimeTeleportDestination destination = _acceptedDestination;
+        return destination.TeleportSequence == teleportSequence
+            && destination.CellId != 0u
+            && destination.CellId == destinationCell;
+    }
+
     public bool TryBeginPortalReveal(
         ushort teleportSequence,
         uint destinationCell,
         out long generation)
     {
         generation = 0;
-        if (!_teleportActive
-            || teleportSequence != _activeTeleportSequence
-            || !_hasAcceptedDestination)
+        if (!CanBeginPortalReveal(teleportSequence, destinationCell))
         {
             LogRejected(
                 "portal-begin-without-destination",
@@ -89,19 +173,6 @@ public sealed class RuntimeWorldTransitState
         }
 
         RuntimeTeleportDestination destination = _acceptedDestination;
-        if (destination.TeleportSequence != teleportSequence
-            || destination.CellId == 0u
-            || destination.CellId != destinationCell)
-        {
-            FailInvariant(
-                "portal-begin-destination-mismatch",
-                $"sequence={teleportSequence} "
-                + $"acceptedSequence={destination.TeleportSequence} "
-                + $"expectedCell=0x{destination.CellId:X8} "
-                + $"actualCell=0x{destinationCell:X8}");
-            return false;
-        }
-
         generation = BeginRevealCore(
             RuntimePortalKind.Portal,
             destinationCell);
@@ -110,6 +181,159 @@ public sealed class RuntimeWorldTransitState
         return true;
     }
 
+    /// <summary>
+    /// Registers one presentation-independent host projection against the
+    /// exact active reveal. Graphical and direct hosts receive the same token.
+    /// </summary>
+    public bool TryRegisterHostProjection(
+        long generation,
+        uint destinationCell,
+        out RuntimeWorldHostProjectionToken token)
+    {
+        token = new RuntimeWorldHostProjectionToken(
+            generation,
+            destinationCell);
+        if (!token.IsValid
+            || generation != _snapshot.Generation
+            || destinationCell != _snapshot.DestinationCell
+            || _snapshot.Cancelled
+            || _snapshot.Completed)
+        {
+            LogRejected(
+                "host-register-mismatch",
+                $"generation={generation} "
+                + $"cell=0x{destinationCell:X8}");
+            token = default;
+            return false;
+        }
+
+        if (_hostProjections.TryGetValue(
+                generation,
+                out HostProjectionRecord? existing))
+        {
+            if (existing.Token == token)
+                return true;
+
+            LogRejected(
+                "host-register-conflict",
+                $"generation={generation} "
+                + $"expectedCell=0x{existing.Token.DestinationCell:X8} "
+                + $"actualCell=0x{destinationCell:X8}");
+            token = default;
+            return false;
+        }
+
+        _hostProjections.Add(
+            generation,
+            new HostProjectionRecord(token));
+        return true;
+    }
+
+    public bool TryGetHostProjection(
+        in RuntimeWorldHostProjectionToken token,
+        out RuntimeWorldHostProjectionSnapshot projection)
+    {
+        if (token.IsValid
+            && _hostProjections.TryGetValue(
+                token.Generation,
+                out HostProjectionRecord? host)
+            && host.Token == token)
+        {
+            projection = host.Snapshot;
+            return true;
+        }
+
+        projection = default;
+        return false;
+    }
+
+    /// <summary>
+    /// Marks the graphical reservation-release callback as due before the
+    /// host executes it. A thrown callback therefore leaves an exact pending
+    /// acknowledgement instead of losing the unfinished suffix.
+    /// </summary>
+    public bool RequireDestinationReservationRelease(
+        in RuntimeWorldHostProjectionToken token)
+    {
+        if (!TryGetHostRecord(token, out HostProjectionRecord? host))
+            return false;
+        if (host.DestinationReservationReleased)
+            return false;
+
+        host.Pending |= RuntimeWorldHostAcknowledgementStage
+            .DestinationReservationReleased;
+        return true;
+    }
+
+    /// <summary>
+    /// Converts an older host projection into an exact withdrawal transaction
+    /// while a replacement reveal keeps world simulation quiesced.
+    /// </summary>
+    public bool BeginHostProjectionSupersession(
+        in RuntimeWorldHostProjectionToken token)
+    {
+        if (!TryGetHostRecord(token, out HostProjectionRecord? host))
+            return false;
+
+        BeginHostProjectionSupersession(host);
+        return true;
+    }
+
+    public bool AcknowledgeHostProjection(
+        in RuntimeWorldHostAcknowledgement acknowledgement)
+    {
+        RuntimeWorldHostAcknowledgementStage stage =
+            acknowledgement.Stage;
+        if (!IsSingleStage(stage)
+            || !TryGetHostRecord(
+                acknowledgement.Projection,
+                out HostProjectionRecord? host)
+            || (host.Pending & stage) == 0)
+        {
+            return false;
+        }
+
+        switch (stage)
+        {
+            case RuntimeWorldHostAcknowledgementStage.ProjectionRegistered:
+                if (host.IsSuperseding)
+                    return false;
+                host.ProjectionRegistered = true;
+                break;
+            case RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected:
+                if (host.Token.Generation == _snapshot.Generation
+                    && !_snapshot.WorldSimulationAvailable)
+                {
+                    return false;
+                }
+                host.SimulationReleaseProjected = true;
+                break;
+            case RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased:
+                host.DestinationReservationReleased = true;
+                break;
+            case RuntimeWorldHostAcknowledgementStage.TerminalProjected:
+                if (!host.IsSuperseding
+                    && (host.Token.Generation != _snapshot.Generation
+                        || (!_snapshot.Completed
+                            && !_snapshot.Cancelled)))
+                {
+                    return false;
+                }
+                if ((host.Pending & ~stage) != 0)
+                    return false;
+                host.Pending &= ~stage;
+                _hostProjections.Remove(host.Token.Generation);
+                return true;
+            default:
+                return false;
+        }
+
+        host.Pending &= ~stage;
+        return true;
+    }
+
     private long BeginRevealCore(
         RuntimePortalKind kind,
         uint destinationCell)
@@ -125,6 +349,12 @@ public sealed class RuntimeWorldTransitState
         {
             Log("superseded", _snapshot);
         }
+        if (_hostProjections.TryGetValue(
+                _snapshot.Generation,
+                out HostProjectionRecord? superseded))
+        {
+            BeginHostProjectionSupersession(superseded);
+        }
 
         long generation = checked(++_nextGeneration);
         int failures = _snapshot.InvariantFailureCount;
@@ -372,6 +602,10 @@ public sealed class RuntimeWorldTransitState
             WorldSimulationAvailable = true,
             PortalMaterializationCount = count,
         };
+        RequireHostStage(
+            generation,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected);
         Log("materialized", _snapshot);
         return true;
     }
@@ -444,11 +678,16 @@ public sealed class RuntimeWorldTransitState
             return false;
         }
 
+        bool simulationWasAvailable =
+            _snapshot.WorldSimulationAvailable;
         _snapshot = _snapshot with
         {
             Completed = true,
             WorldSimulationAvailable = true,
         };
+        RequireTerminalHostProjection(
+            generation,
+            requireSimulationRelease: !simulationWasAvailable);
         Log("complete", _snapshot);
         return true;
     }
@@ -463,11 +702,16 @@ public sealed class RuntimeWorldTransitState
             return false;
         }
 
+        bool simulationWasAvailable =
+            _snapshot.WorldSimulationAvailable;
         _snapshot = _snapshot with
         {
             Cancelled = true,
             WorldSimulationAvailable = true,
         };
+        RequireTerminalHostProjection(
+            generation,
+            requireSimulationRelease: !simulationWasAvailable);
         Log("cancel", _snapshot);
         return true;
     }
@@ -479,6 +723,17 @@ public sealed class RuntimeWorldTransitState
     /// </summary>
     public void ResetSession()
     {
+        if (_hostProjections.Count != 0)
+        {
+            RuntimeWorldTransitOwnershipSnapshot ownership =
+                CaptureOwnership();
+            throw new InvalidOperationException(
+                "World transit cannot reset while a host projection "
+                + "still owns an acknowledgement suffix "
+                + $"(hosts={ownership.HostProjectionCount}, "
+                + $"pending={ownership.PendingHostAcknowledgementCount}).");
+        }
+
         _snapshot = RuntimePortalSnapshot.Idle;
         EndTeleport();
         _hasLastTeleportStart = false;
@@ -486,6 +741,105 @@ public sealed class RuntimeWorldTransitState
         _bufferedDestinations.Clear();
     }
 
+    private bool TryGetHostRecord(
+        in RuntimeWorldHostProjectionToken token,
+        out HostProjectionRecord host)
+    {
+        if (token.IsValid
+            && _hostProjections.TryGetValue(
+                token.Generation,
+                out HostProjectionRecord? candidate)
+            && candidate.Token == token)
+        {
+            host = candidate;
+            return true;
+        }
+
+        host = null!;
+        return false;
+    }
+
+    private void RequireHostStage(
+        long generation,
+        RuntimeWorldHostAcknowledgementStage stage)
+    {
+        if (!_hostProjections.TryGetValue(
+                generation,
+                out HostProjectionRecord? host))
+        {
+            return;
+        }
+
+        bool alreadyAcknowledged = stage switch
+        {
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered =>
+                host.ProjectionRegistered,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected =>
+                host.SimulationReleaseProjected,
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased =>
+                host.DestinationReservationReleased,
+            _ => false,
+        };
+        if (!alreadyAcknowledged)
+            host.Pending |= stage;
+    }
+
+    private void RequireTerminalHostProjection(
+        long generation,
+        bool requireSimulationRelease)
+    {
+        if (!_hostProjections.TryGetValue(
+                generation,
+                out HostProjectionRecord? host))
+        {
+            return;
+        }
+
+        // A host that is terminating no longer has to finish acquiring a
+        // projection. It must instead release every resource it did acquire.
+        host.Pending &=
+            ~RuntimeWorldHostAcknowledgementStage.ProjectionRegistered;
+        if (requireSimulationRelease
+            && !host.SimulationReleaseProjected)
+        {
+            host.Pending |= RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected;
+        }
+        if (!host.DestinationReservationReleased)
+        {
+            host.Pending |= RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased;
+        }
+        host.Pending |=
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected;
+    }
+
+    private static void BeginHostProjectionSupersession(
+        HostProjectionRecord host)
+    {
+        host.IsSuperseding = true;
+        host.Pending &=
+            ~(RuntimeWorldHostAcknowledgementStage.ProjectionRegistered
+                | RuntimeWorldHostAcknowledgementStage
+                    .SimulationReleaseProjected);
+        if (!host.DestinationReservationReleased)
+        {
+            host.Pending |= RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased;
+        }
+        host.Pending |=
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected;
+    }
+
+    private static bool IsSingleStage(
+        RuntimeWorldHostAcknowledgementStage stage)
+    {
+        int value = (int)stage;
+        return value != 0 && (value & (value - 1)) == 0;
+    }
+
     private bool IsCurrentPortalDestination(
         long generation,
         ushort teleportSequence,

tests/AcDream.App.Tests/Diagnostics/WorldLifecycleAutomationControllerTests.cs

@@ -6,6 +6,7 @@ using AcDream.App.Rendering.Scene;
 using AcDream.App.Streaming;
 using AcDream.App.UI.Testing;
 using AcDream.Runtime;
+using AcDream.Runtime.World;
 using SixLabors.ImageSharp;
 
 namespace AcDream.App.Tests.Diagnostics;
@@ -179,6 +180,19 @@ public sealed class WorldLifecycleAutomationControllerTests
             Path.Combine(directory, "screenshots"));
         var controller = new WorldLifecycleAutomationController(
             () => reveal,
+            () => new RuntimeWorldEnvironmentOwnershipSnapshot(
+                IsInitialized: true,
+                DayGroupDefinitionCount: 4,
+                ActiveDayGroupCount: 1),
+            () => new RuntimeWorldTransitOwnershipSnapshot(
+                BufferedTeleportDestinationCount: 0,
+                PendingTeleportStartCount: 0,
+                ActiveTeleportCount: 0,
+                AcceptedTeleportDestinationCount: 0,
+                ActiveRevealCount: 0,
+                PendingDestinationReadinessCount: 0,
+                HostProjectionCount: 0,
+                PendingHostAcknowledgementCount: 0),
             () => 3,
             _ => resources,
             screenshots,
@@ -205,6 +219,15 @@ public sealed class WorldLifecycleAutomationControllerTests
             using JsonDocument json = JsonDocument.Parse(line);
             Assert.Equal("dungeon", json.RootElement.GetProperty("name").GetString());
             Assert.Equal(7, json.RootElement.GetProperty("reveal").GetProperty("generation").GetInt64());
+            Assert.Equal(
+                4,
+                json.RootElement.GetProperty("environmentOwnership")
+                    .GetProperty("dayGroupDefinitionCount").GetInt32());
+            Assert.Equal(
+                0,
+                json.RootElement.GetProperty("transitOwnership")
+                    .GetProperty("pendingHostAcknowledgementCount")
+                    .GetInt32());
             Assert.Equal(4, json.RootElement.GetProperty("render").GetProperty("world")
                 .GetProperty("visibleLandblocks").GetInt32());
             Assert.True(json.RootElement.GetProperty("render").GetProperty("presentation")
@@ -373,6 +396,8 @@ public sealed class WorldLifecycleAutomationControllerTests
         string directory,
         Func<RenderFrameOutcome, WorldLifecycleResourceSnapshot> capture) =>
         new(
+            () => default,
+            () => default,
             () => default,
             () => 0,
             capture,

tests/AcDream.App.Tests/Runtime/RuntimeWorldTransitOwnershipTests.cs

@@ -81,7 +81,34 @@ public sealed class RuntimeWorldTransitOwnershipTests
             coordinatorFields,
             field => field.Name is "_activeGeneration"
                 or "_worldSimulationReleased"
-                or "_lifecycle");
+                or "_lifecycle"
+                or "_reservationGeneration"
+                or "_worldViewportReleased"
+                or "_hostProjection");
+        Assert.DoesNotContain(
+            coordinatorFields,
+            field => field.FieldType == typeof(RuntimePortalSnapshot)
+                || field.FieldType == typeof(RuntimeDestinationReadiness)
+                || field.FieldType == typeof(long)
+                || field.FieldType == typeof(uint));
+
+        Type hostProjection = Assert.Single(
+            typeof(WorldRevealCoordinator).GetNestedTypes(
+                System.Reflection.BindingFlags.NonPublic),
+            type => type.Name == "HostProjection");
+        var hostFields = hostProjection.GetFields(
+            System.Reflection.BindingFlags.Instance
+            | System.Reflection.BindingFlags.NonPublic);
+        Assert.Single(
+            hostFields,
+            field => field.FieldType
+                == typeof(RuntimeWorldHostProjectionToken));
+        Assert.DoesNotContain(
+            hostFields,
+            field => field.FieldType == typeof(RuntimePortalSnapshot)
+                || field.FieldType == typeof(RuntimeDestinationReadiness)
+                || field.FieldType == typeof(long)
+                || field.FieldType == typeof(uint));
 
         var teleportFields = typeof(LocalPlayerTeleportController)
             .GetFields(

tests/AcDream.App.Tests/Streaming/WorldGenerationQuiescenceTests.cs

@@ -144,6 +144,39 @@ public sealed class WorldGenerationQuiescenceTests
         Assert.Equal(inventoryGuid, selection.SelectedObjectId);
     }
 
+    [Fact]
+    public void ReentrantBeginDuringAudioResume_ReconcilesToNewestEdge()
+    {
+        var transit = new RuntimeWorldTransitState();
+        var world = new GpuWorldState(
+            availability: new WorldGenerationAvailabilityState(transit));
+        var audio = new ReentrantAudioQuiescence();
+        var quiescence = new WorldGenerationQuiescence(
+            new SelectionState(),
+            world,
+            _ => null,
+            audio);
+        var edge = new WorldGenerationQuiescenceEdge(
+            ShouldApply: true,
+            ClearWorldSelection: false);
+        quiescence.CommitBegin(edge);
+        audio.OnResume = () =>
+        {
+            audio.OnResume = null;
+            quiescence.CommitBegin(edge);
+        };
+
+        quiescence.ObserveReleased();
+
+        Assert.Equal(2, audio.SuspendCalls);
+        Assert.Equal(1, audio.ResumeCalls);
+
+        quiescence.ObserveReleased();
+
+        Assert.Equal(2, audio.SuspendCalls);
+        Assert.Equal(2, audio.ResumeCalls);
+    }
+
     private static RuntimeDestinationReadiness Ready(
         long generation,
         uint destinationCell) =>
@@ -178,4 +211,19 @@ public sealed class WorldGenerationQuiescenceTests
         public void SuspendWorldAudio() => SuspendCalls++;
         public void ResumeWorldAudio() => ResumeCalls++;
     }
+
+    private sealed class ReentrantAudioQuiescence : IWorldAudioQuiescence
+    {
+        public int SuspendCalls { get; private set; }
+        public int ResumeCalls { get; private set; }
+        public Action? OnResume { get; set; }
+
+        public void SuspendWorldAudio() => SuspendCalls++;
+
+        public void ResumeWorldAudio()
+        {
+            ResumeCalls++;
+            OnResume?.Invoke();
+        }
+    }
 }

tests/AcDream.App.Tests/Streaming/WorldRevealCoordinatorTests.cs

@@ -409,8 +409,9 @@ public sealed class WorldRevealCoordinatorTests
                 (second, 0x20210123u, 0),
             ],
             scheduler.Begins);
-        coordinator.Complete();
-        Assert.Equal([second], scheduler.Ends);
+        Assert.Equal([first], scheduler.Ends);
+        coordinator.Cancel();
+        Assert.Equal([first, second], scheduler.Ends);
     }
 
     [Fact]
@@ -434,10 +435,200 @@ public sealed class WorldRevealCoordinatorTests
             sequence: 2);
 
         Assert.Equal([first, second], resources.Begins);
+        Assert.Equal([first], resources.Ends);
         coordinator.RevealWorldViewport();
         coordinator.Complete();
 
-        Assert.Equal([second], resources.Ends);
+        Assert.Equal([first, second], resources.Ends);
+    }
+
+    [Fact]
+    public void RegistrationCallback_ReentrantReplacementRetiresExactOldSuffix()
+    {
+        var state = new State();
+        var scheduler = new RecordingDestinationScheduler();
+        WorldRevealCoordinator coordinator = null!;
+        long replacement = 0;
+        scheduler.OnBegin = () =>
+        {
+            scheduler.OnBegin = null;
+            replacement = coordinator.BeginLogin(0x20210123u);
+        };
+        coordinator = state.Build(streaming: scheduler);
+
+        long first = coordinator.BeginLogin(0x11340021u);
+
+        Assert.NotEqual(first, replacement);
+        Assert.Equal(replacement, coordinator.Snapshot.Generation);
+        Assert.Equal(
+            [
+                (first, 0x11340021u, 1),
+                (replacement, 0x20210123u, 0),
+            ],
+            scheduler.Begins);
+        Assert.Equal([first], scheduler.Ends);
+        Assert.Equal(1, coordinator.Ownership.HostProjectionCount);
+        Assert.Equal(
+            0,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+
+        coordinator.Cancel();
+
+        Assert.Equal([first, replacement], scheduler.Ends);
+        Assert.Equal(0, coordinator.Ownership.HostProjectionCount);
+    }
+
+    [Fact]
+    public void RegistrationFailure_RetriesExactSuffixWithoutReplayingBegin()
+    {
+        var state = new State();
+        var scheduler = new RecordingDestinationScheduler();
+        var resources = new RecordingRenderResourceScheduler
+        {
+            ThrowBeginCount = 1,
+        };
+        WorldRevealCoordinator coordinator = state.Build(
+            streaming: scheduler,
+            renderResources: resources);
+
+        Assert.Throws<InvalidOperationException>(
+            () => coordinator.BeginLogin(0x11340021u));
+        Assert.Single(scheduler.Begins);
+        Assert.Equal(1, resources.BeginAttempts);
+        Assert.Empty(resources.Begins);
+        Assert.Equal(1, coordinator.Ownership.HostProjectionCount);
+        Assert.Equal(
+            1,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+
+        coordinator.RetryPendingHostWork();
+
+        Assert.Single(scheduler.Begins);
+        Assert.Equal(2, resources.BeginAttempts);
+        Assert.Single(resources.Begins);
+        Assert.Equal(
+            0,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+
+        coordinator.Cancel();
+        Assert.Equal(0, coordinator.Ownership.HostProjectionCount);
+    }
+
+    [Fact]
+    public void ReservationReleaseFailure_RetriesOnlyUnfinishedCallback()
+    {
+        var state = new State();
+        var scheduler = new RecordingDestinationScheduler();
+        var resources = new RecordingRenderResourceScheduler
+        {
+            ThrowEndCount = 1,
+        };
+        WorldRevealCoordinator coordinator = state.Build(
+            streaming: scheduler,
+            renderResources: resources);
+        long generation = coordinator.BeginLogin(0x11340021u);
+
+        Assert.Throws<InvalidOperationException>(
+            coordinator.RevealWorldViewport);
+        Assert.Equal([generation], scheduler.Ends);
+        Assert.Equal(1, resources.EndAttempts);
+        Assert.Empty(resources.Ends);
+        Assert.Equal(
+            1,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+
+        coordinator.RetryPendingHostWork();
+
+        Assert.Equal([generation], scheduler.Ends);
+        Assert.Equal(2, resources.EndAttempts);
+        Assert.Equal([generation], resources.Ends);
+        Assert.Equal(
+            0,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+        coordinator.Cancel();
+    }
+
+    [Fact]
+    public void ResetFailure_RetainsWithdrawalAndConvergesOnRetry()
+    {
+        var state = new State();
+        var scheduler = new RecordingDestinationScheduler
+        {
+            ThrowEndCount = 1,
+        };
+        WorldRevealCoordinator coordinator =
+            state.Build(streaming: scheduler);
+        coordinator.BeginLogin(0x11340021u);
+
+        Assert.Throws<InvalidOperationException>(coordinator.ResetSession);
+        Assert.True(coordinator.Snapshot.Cancelled);
+        Assert.Equal(1, coordinator.Ownership.HostProjectionCount);
+        Assert.True(
+            coordinator.Ownership.PendingHostAcknowledgementCount > 0);
+
+        coordinator.ResetSession();
+
+        Assert.Equal(RuntimePortalSnapshot.Idle, coordinator.Snapshot);
+        Assert.True(coordinator.Ownership.IsSessionIdle);
+        Assert.Equal(2, scheduler.EndAttempts);
+        Assert.Single(scheduler.Ends);
+    }
+
+    [Fact]
+    public void SimulationReleaseFailure_RetriesAudioWithoutReplayingMaterialization()
+    {
+        var transit = new RuntimeWorldTransitState();
+        var availability = new WorldGenerationAvailabilityState(transit);
+        var world = new GpuWorldState(availability: availability);
+        var audio = new RecordingAudioQuiescence
+        {
+            ThrowResumeCount = 1,
+        };
+        var quiescence = new WorldGenerationQuiescence(
+            new SelectionState(),
+            world,
+            _ => null,
+            audio);
+        var coordinator = new WorldRevealCoordinator(
+            transit,
+            isRenderNeighborhoodReady: (_, _) => true,
+            isSpawnCellReady: _ => true,
+            isTerrainNeighborhoodReady: (_, _) => true,
+            areCompositeTexturesReady: () => true,
+            prepareCompositeTextures: (_, _) => { },
+            invalidateCompositeTextures: () => { },
+            isSpawnClaimUnhydratable: _ => false,
+            quiescence: quiescence);
+        const uint cell = 0x3032001Cu;
+        long generation = BeginPortal(
+            coordinator,
+            transit,
+            cell,
+            sequence: 1);
+        Assert.True(coordinator.Evaluate(cell).IsReady);
+
+        Assert.Throws<InvalidOperationException>(() =>
+            coordinator.ObserveMaterialized(
+                generation,
+                1,
+                cell));
+        Assert.True(coordinator.Snapshot.Materialized);
+        Assert.Equal(1, coordinator.PortalMaterializationCount);
+        Assert.Equal(1, audio.ResumeAttempts);
+        Assert.Equal(0, audio.ResumeCalls);
+        Assert.Equal(
+            1,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+
+        coordinator.RetryPendingHostWork();
+
+        Assert.Equal(2, audio.ResumeAttempts);
+        Assert.Equal(1, audio.ResumeCalls);
+        Assert.Equal(1, coordinator.PortalMaterializationCount);
+        Assert.Equal(
+            0,
+            coordinator.Ownership.PendingHostAcknowledgementCount);
+        coordinator.Cancel();
     }
 
     private static long BeginPortal(
@@ -471,9 +662,32 @@ public sealed class WorldRevealCoordinatorTests
     {
         public int SuspendCalls { get; private set; }
         public int ResumeCalls { get; private set; }
+        public int SuspendAttempts { get; private set; }
+        public int ResumeAttempts { get; private set; }
+        public int ThrowSuspendCount { get; set; }
+        public int ThrowResumeCount { get; set; }
 
-        public void SuspendWorldAudio() => SuspendCalls++;
-        public void ResumeWorldAudio() => ResumeCalls++;
+        public void SuspendWorldAudio()
+        {
+            SuspendAttempts++;
+            if (ThrowSuspendCount > 0)
+            {
+                ThrowSuspendCount--;
+                throw new InvalidOperationException("suspend failed");
+            }
+            SuspendCalls++;
+        }
+
+        public void ResumeWorldAudio()
+        {
+            ResumeAttempts++;
+            if (ThrowResumeCount > 0)
+            {
+                ThrowResumeCount--;
+                throw new InvalidOperationException("resume failed");
+            }
+            ResumeCalls++;
+        }
     }
 
     private sealed class RecordingDestinationScheduler
@@ -481,16 +695,40 @@ public sealed class WorldRevealCoordinatorTests
     {
         public List<(long Generation, uint Cell, int Radius)> Begins { get; } = [];
         public List<long> Ends { get; } = [];
+        public int BeginAttempts { get; private set; }
+        public int EndAttempts { get; private set; }
+        public int ThrowBeginCount { get; set; }
+        public int ThrowEndCount { get; set; }
+        public Action? OnBegin { get; set; }
+        public Action? OnEnd { get; set; }
 
         public void BeginDestinationReservation(
             long revealGeneration,
             uint destinationCell,
-            int requiredRenderRadius) =>
+            int requiredRenderRadius)
+        {
+            BeginAttempts++;
+            if (ThrowBeginCount > 0)
+            {
+                ThrowBeginCount--;
+                throw new InvalidOperationException("stream begin failed");
+            }
             Begins.Add(
                 (revealGeneration, destinationCell, requiredRenderRadius));
+            OnBegin?.Invoke();
+        }
 
-        public void EndDestinationReservation(long revealGeneration) =>
+        public void EndDestinationReservation(long revealGeneration)
+        {
+            EndAttempts++;
+            if (ThrowEndCount > 0)
+            {
+                ThrowEndCount--;
+                throw new InvalidOperationException("stream end failed");
+            }
             Ends.Add(revealGeneration);
+            OnEnd?.Invoke();
+        }
     }
 
     private sealed class RecordingRenderResourceScheduler
@@ -498,11 +736,31 @@ public sealed class WorldRevealCoordinatorTests
     {
         public List<long> Begins { get; } = [];
         public List<long> Ends { get; } = [];
+        public int BeginAttempts { get; private set; }
+        public int EndAttempts { get; private set; }
+        public int ThrowBeginCount { get; set; }
+        public int ThrowEndCount { get; set; }
 
-        public void BeginDestinationReveal(long revealGeneration) =>
+        public void BeginDestinationReveal(long revealGeneration)
+        {
+            BeginAttempts++;
+            if (ThrowBeginCount > 0)
+            {
+                ThrowBeginCount--;
+                throw new InvalidOperationException("render begin failed");
+            }
             Begins.Add(revealGeneration);
+        }
 
-        public void EndDestinationReveal(long revealGeneration) =>
+        public void EndDestinationReveal(long revealGeneration)
+        {
+            EndAttempts++;
+            if (ThrowEndCount > 0)
+            {
+                ThrowEndCount--;
+                throw new InvalidOperationException("render end failed");
+            }
             Ends.Add(revealGeneration);
         }
+    }
 }

tests/AcDream.Runtime.Tests/GameRuntimeContractTests.cs

@@ -1,5 +1,6 @@
 using System.Reflection;
 using AcDream.Runtime.Gameplay;
+using AcDream.Runtime.World;
 
 namespace AcDream.Runtime.Tests;
 
@@ -183,7 +184,20 @@ public sealed class GameRuntimeContractTests
                 InteractionTransactions: default),
             default,
             default,
-            default);
+            new RuntimeWorldEnvironmentOwnershipSnapshot(
+                IsInitialized: true,
+                DayGroupDefinitionCount: 4,
+                ActiveDayGroupCount: 1),
+            default,
+            new RuntimeWorldTransitOwnershipSnapshot(
+                BufferedTeleportDestinationCount: 0,
+                PendingTeleportStartCount: 0,
+                ActiveTeleportCount: 1,
+                AcceptedTeleportDestinationCount: 0,
+                ActiveRevealCount: 1,
+                PendingDestinationReadinessCount: 1,
+                HostProjectionCount: 1,
+                PendingHostAcknowledgementCount: 2));
 
         recorder.AddCheckpoint(stamp, checkpoint);
 
@@ -191,6 +205,8 @@ public sealed class GameRuntimeContractTests
         Assert.Contains("inventory-state=2:4:1:3", entry.Text);
         Assert.Contains("character=5:6:7:8:0:0", entry.Text);
         Assert.Contains("social=9:10:11", entry.Text);
+        Assert.Contains("environment-owner=True:4:1", entry.Text);
+        Assert.Contains("transit-owner=0:0:1:0:1:1:1:2", entry.Text);
         Assert.Contains(
             "actions=14:50000001:15:4:1:16:1:00000000:0:00000000:" +
             "00000000:00000000:00000000:0:0:0:0:00000000:00000000:" +

tests/AcDream.Runtime.Tests/World/RuntimeWorldTransitDirectHostTests.cs

@@ -0,0 +1,204 @@
+using System.Numerics;
+using AcDream.Core.Physics;
+using AcDream.Runtime.World;
+
+namespace AcDream.Runtime.Tests.World;
+
+public sealed class RuntimeWorldTransitDirectHostTests
+{
+    private static readonly string[] ForbiddenHostAssemblyPrefixes =
+    [
+        "AcDream.App",
+        "AcDream.UI.",
+        "Silk.NET",
+        "OpenAL",
+        "Arch",
+        "ImGui",
+    ];
+
+    private const uint OutdoorCell = 0x11340021u;
+    private const uint IndoorCell = 0x8A020164u;
+
+    [Fact]
+    public void DirectHost_CompletesLoginPortalCancellationAndReset()
+    {
+        string[] loadedAssemblies = AppDomain.CurrentDomain.GetAssemblies()
+            .Select(static assembly =>
+                assembly.GetName().Name ?? string.Empty)
+            .ToArray();
+        Assert.DoesNotContain(
+            loadedAssemblies,
+            name => ForbiddenHostAssemblyPrefixes.Any(
+                prefix => name.StartsWith(
+                    prefix,
+                    StringComparison.OrdinalIgnoreCase)));
+
+        var state = new RuntimeWorldTransitState();
+        var host = new DirectHost(state);
+
+        host.CompleteLogin(OutdoorCell);
+        Assert.True(state.Snapshot.Completed);
+        Assert.True(state.Snapshot.WorldViewportObserved);
+        Assert.Equal(0, state.Ownership.HostProjectionCount);
+
+        state.ResetSession();
+        host.CompletePortal(IndoorCell, sequence: 1);
+        Assert.True(state.Snapshot.Completed);
+        Assert.True(state.Snapshot.Materialized);
+        Assert.Equal(1, state.Snapshot.PortalMaterializationCount);
+        Assert.Equal(0, state.Ownership.PendingHostAcknowledgementCount);
+
+        state.EndTeleport();
+        state.ResetSession();
+        host.CancelLogin(OutdoorCell);
+        Assert.True(state.Snapshot.Cancelled);
+        Assert.Equal(0, state.Ownership.HostProjectionCount);
+
+        state.ResetSession();
+        Assert.Equal(RuntimePortalSnapshot.Idle, state.Snapshot);
+        Assert.True(state.Ownership.IsSessionIdle);
+    }
+
+    private sealed class DirectHost(RuntimeWorldTransitState state)
+    {
+        public void CompleteLogin(uint cell)
+        {
+            long generation = state.BeginLoginReveal(cell);
+            RuntimeWorldHostProjectionToken host =
+                Register(generation, cell);
+            Acknowledge(
+                host,
+                RuntimeWorldHostAcknowledgementStage.ProjectionRegistered);
+            Assert.True(state.AcknowledgeDestinationReadiness(
+                Ready(generation, cell)));
+            Assert.True(state.Complete(generation));
+            DrainPending(host);
+            Assert.True(state.AcknowledgeWorldViewportVisible(generation));
+        }
+
+        public void CompletePortal(uint cell, ushort sequence)
+        {
+            Assert.True(state.TryQueueTeleportStart(sequence));
+            Assert.True(state.ActivateQueuedTeleport());
+            Assert.True(state.OfferTeleportDestination(
+                Destination(cell, sequence),
+                teleportTimestampAdvanced: true));
+            Assert.True(state.TryBeginPortalReveal(
+                sequence,
+                cell,
+                out long generation));
+            RuntimeWorldHostProjectionToken host =
+                Register(generation, cell);
+            Acknowledge(
+                host,
+                RuntimeWorldHostAcknowledgementStage.ProjectionRegistered);
+            Assert.True(state.AcknowledgeDestinationReadiness(
+                Ready(generation, cell)));
+            Assert.True(state.AcknowledgePortalMaterialized(
+                generation,
+                sequence,
+                cell));
+            DrainPending(host);
+            Assert.True(state.RequireDestinationReservationRelease(host));
+            DrainPending(host);
+            Assert.True(state.AcknowledgeWorldViewportVisible(generation));
+            Assert.True(state.Complete(generation));
+            DrainPending(host);
+        }
+
+        public void CancelLogin(uint cell)
+        {
+            long generation = state.BeginLoginReveal(cell);
+            RuntimeWorldHostProjectionToken host =
+                Register(generation, cell);
+            Acknowledge(
+                host,
+                RuntimeWorldHostAcknowledgementStage.ProjectionRegistered);
+            Assert.True(state.Cancel(generation));
+            DrainPending(host);
+        }
+
+        private RuntimeWorldHostProjectionToken Register(
+            long generation,
+            uint cell)
+        {
+            Assert.True(state.TryRegisterHostProjection(
+                generation,
+                cell,
+                out RuntimeWorldHostProjectionToken host));
+            return host;
+        }
+
+        private void DrainPending(RuntimeWorldHostProjectionToken host)
+        {
+            while (state.TryGetHostProjection(
+                host,
+                out RuntimeWorldHostProjectionSnapshot projection))
+            {
+                RuntimeWorldHostAcknowledgementStage pending =
+                    projection.PendingAcknowledgements;
+                if ((pending & RuntimeWorldHostAcknowledgementStage
+                        .SimulationReleaseProjected) != 0)
+                {
+                    Acknowledge(
+                        host,
+                        RuntimeWorldHostAcknowledgementStage
+                            .SimulationReleaseProjected);
+                    continue;
+                }
+                if ((pending & RuntimeWorldHostAcknowledgementStage
+                        .DestinationReservationReleased) != 0)
+                {
+                    Acknowledge(
+                        host,
+                        RuntimeWorldHostAcknowledgementStage
+                            .DestinationReservationReleased);
+                    continue;
+                }
+                if ((pending & RuntimeWorldHostAcknowledgementStage
+                        .TerminalProjected) != 0)
+                {
+                    Acknowledge(
+                        host,
+                        RuntimeWorldHostAcknowledgementStage
+                            .TerminalProjected);
+                    continue;
+                }
+                break;
+            }
+        }
+
+        private void Acknowledge(
+            RuntimeWorldHostProjectionToken host,
+            RuntimeWorldHostAcknowledgementStage stage) =>
+            Assert.True(state.AcknowledgeHostProjection(
+                new RuntimeWorldHostAcknowledgement(host, stage)));
+    }
+
+    private static RuntimeDestinationReadiness Ready(
+        long generation,
+        uint cell) =>
+        new(
+            generation,
+            cell,
+            IsIndoor: (cell & 0xFFFFu) >= 0x0100u,
+            IsUnhydratable: false,
+            RequiredRenderRadius: (cell & 0xFFFFu) >= 0x0100u ? 0 : 1,
+            IsRenderNeighborhoodReady: true,
+            AreCompositeTexturesReady: true,
+            IsCollisionReady: true);
+
+    private static RuntimeTeleportDestination Destination(
+        uint cell,
+        ushort sequence) =>
+        new(
+            EntityGuid: 0x50000001u,
+            InstanceSequence: 1,
+            PositionSequence: 1,
+            TeleportSequence: sequence,
+            ForcePositionSequence: 1,
+            Position: new Position(
+                cell,
+                Vector3.Zero,
+                Quaternion.Identity));
+}

tests/AcDream.Runtime.Tests/World/RuntimeWorldTransitStateTests.cs

@@ -338,6 +338,18 @@ public sealed class RuntimeWorldTransitStateTests
             BeginPortal(first, OutdoorCell);
         long secondGeneration =
             second.BeginLoginReveal(OtherCell);
+        RuntimeWorldHostProjectionToken firstHost =
+            RegisterHost(first, firstGeneration, OutdoorCell);
+        RuntimeWorldHostProjectionToken secondHost =
+            RegisterHost(second, secondGeneration, OtherCell);
+        Assert.True(Acknowledge(
+            first,
+            firstHost,
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered));
+        Assert.True(Acknowledge(
+            second,
+            secondHost,
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered));
         first.AcknowledgeDestinationReadiness(
             Ready(firstGeneration, OutdoorCell));
         first.AcknowledgePortalMaterialized(
@@ -351,6 +363,13 @@ public sealed class RuntimeWorldTransitStateTests
         Assert.False(second.IsWorldSimulationAvailable);
         Assert.Equal(OtherCell, second.Snapshot.DestinationCell);
         Assert.Equal(1, secondGeneration);
+        Assert.False(Acknowledge(
+            second,
+            firstHost,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected));
+        Assert.Equal(1, first.Ownership.PendingHostAcknowledgementCount);
+        Assert.Equal(0, second.Ownership.PendingHostAcknowledgementCount);
     }
 
     [Fact]
@@ -616,6 +635,195 @@ public sealed class RuntimeWorldTransitStateTests
         Assert.True(state.TryQueueTeleportStart(8));
     }
 
+    [Fact]
+    public void HostProjection_TracksExactGenerationScopedAcknowledgementSuffix()
+    {
+        var state = new RuntimeWorldTransitState();
+        long generation = BeginPortal(state, OutdoorCell);
+        RuntimeWorldHostProjectionToken host =
+            RegisterHost(state, generation, OutdoorCell);
+
+        Assert.Equal(
+            new RuntimeWorldTransitOwnershipSnapshot(
+                BufferedTeleportDestinationCount: 0,
+                PendingTeleportStartCount: 0,
+                ActiveTeleportCount: 1,
+                AcceptedTeleportDestinationCount: 0,
+                ActiveRevealCount: 1,
+                PendingDestinationReadinessCount: 1,
+                HostProjectionCount: 1,
+                PendingHostAcknowledgementCount: 1),
+            state.Ownership);
+        Assert.False(Acknowledge(
+            state,
+            host with { Generation = generation + 1 },
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered));
+        Assert.False(Acknowledge(
+            state,
+            host with { DestinationCell = OtherCell },
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered));
+        Assert.False(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.None));
+        Assert.False(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered
+            | RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered));
+
+        Assert.True(state.AcknowledgeDestinationReadiness(
+            Ready(generation, OutdoorCell)));
+        Assert.True(state.AcknowledgePortalMaterialized(
+            generation,
+            1,
+            OutdoorCell));
+        Assert.Equal(1, state.Ownership.PendingHostAcknowledgementCount);
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected));
+
+        Assert.True(state.RequireDestinationReservationRelease(host));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased));
+        Assert.True(state.AcknowledgeWorldViewportVisible(generation));
+        Assert.True(state.Complete(generation));
+        Assert.Equal(1, state.Ownership.PendingHostAcknowledgementCount);
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected));
+        Assert.Equal(0, state.Ownership.HostProjectionCount);
+        Assert.Equal(0, state.Ownership.PendingHostAcknowledgementCount);
+
+        state.EndTeleport();
+        state.ResetSession();
+        Assert.True(state.Ownership.IsSessionIdle);
+    }
+
+    [Fact]
+    public void Cancel_ReplacesIncompleteRegistrationWithRetryableWithdrawal()
+    {
+        var state = new RuntimeWorldTransitState();
+        long generation = state.BeginLoginReveal(OutdoorCell);
+        RuntimeWorldHostProjectionToken host =
+            RegisterHost(state, generation, OutdoorCell);
+
+        Assert.True(state.Cancel(generation));
+        Assert.True(state.TryGetHostProjection(
+            host,
+            out RuntimeWorldHostProjectionSnapshot projection));
+        Assert.Equal(
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected
+            | RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased
+            | RuntimeWorldHostAcknowledgementStage.TerminalProjected,
+            projection.PendingAcknowledgements);
+        Assert.False(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected));
+
+        state.ResetSession();
+        Assert.True(state.Ownership.IsSessionIdle);
+    }
+
+    [Fact]
+    public void Supersession_PreservesOldHostWithdrawalByExactGeneration()
+    {
+        var state = new RuntimeWorldTransitState();
+        long first = state.BeginLoginReveal(OutdoorCell);
+        RuntimeWorldHostProjectionToken firstHost =
+            RegisterHost(state, first, OutdoorCell);
+        Assert.True(Acknowledge(
+            state,
+            firstHost,
+            RuntimeWorldHostAcknowledgementStage.ProjectionRegistered));
+
+        long second = BeginPortal(state, OtherCell, sequence: 2);
+
+        Assert.True(state.TryGetHostProjection(
+            firstHost,
+            out RuntimeWorldHostProjectionSnapshot superseded));
+        Assert.True(superseded.IsSuperseding);
+        Assert.Equal(
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased
+            | RuntimeWorldHostAcknowledgementStage.TerminalProjected,
+            superseded.PendingAcknowledgements);
+        Assert.False(Acknowledge(
+            state,
+            firstHost,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected));
+        Assert.True(Acknowledge(
+            state,
+            firstHost,
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased));
+        Assert.True(Acknowledge(
+            state,
+            firstHost,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected));
+        Assert.Equal(second, state.Snapshot.Generation);
+        Assert.Equal(0, state.Ownership.HostProjectionCount);
+    }
+
+    [Fact]
+    public void ResetSession_RejectsUnacknowledgedHostProjection()
+    {
+        var state = new RuntimeWorldTransitState();
+        long generation = state.BeginLoginReveal(OutdoorCell);
+        RuntimeWorldHostProjectionToken host =
+            RegisterHost(state, generation, OutdoorCell);
+
+        InvalidOperationException error =
+            Assert.Throws<InvalidOperationException>(state.ResetSession);
+        Assert.Contains("hosts=1", error.Message);
+        Assert.Equal(generation, state.Snapshot.Generation);
+
+        Assert.True(state.Cancel(generation));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .SimulationReleaseProjected));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage
+                .DestinationReservationReleased));
+        Assert.True(Acknowledge(
+            state,
+            host,
+            RuntimeWorldHostAcknowledgementStage.TerminalProjected));
+        state.ResetSession();
+    }
+
     private static long BeginPortal(
         RuntimeWorldTransitState state,
         uint cell,
@@ -633,6 +841,25 @@ public sealed class RuntimeWorldTransitStateTests
         return generation;
     }
 
+    private static RuntimeWorldHostProjectionToken RegisterHost(
+        RuntimeWorldTransitState state,
+        long generation,
+        uint cell)
+    {
+        Assert.True(state.TryRegisterHostProjection(
+            generation,
+            cell,
+            out RuntimeWorldHostProjectionToken host));
+        return host;
+    }
+
+    private static bool Acknowledge(
+        RuntimeWorldTransitState state,
+        RuntimeWorldHostProjectionToken host,
+        RuntimeWorldHostAcknowledgementStage stage) =>
+        state.AcknowledgeHostProjection(
+            new RuntimeWorldHostAcknowledgement(host, stage));
+
     private static RuntimeTeleportDestination Destination(
         uint cell,
         ushort sequence,

tools/run-connected-world-lifecycle-gate.ps1

@@ -140,6 +140,8 @@ function Read-Checkpoints([string]$Path) {
 function Validate-Checkpoint([string]$SessionLabel, [object]$Checkpoint) {
     $name = $Checkpoint.name
     $reveal = $Checkpoint.reveal
+    $environmentOwnership = $Checkpoint.environmentOwnership
+    $transitOwnership = $Checkpoint.transitOwnership
     $resources = $Checkpoint.resources
     if (-not $reveal.readiness.isReady) {
         $failures.Add("${SessionLabel}/${name}: reveal was not ready")
@@ -161,6 +163,31 @@ function Validate-Checkpoint([string]$SessionLabel, [object]$Checkpoint) {
             $failures.Add("${SessionLabel}/${name}: collision was not ready")
         }
     }
+    if (-not $environmentOwnership.isInitialized) {
+        $failures.Add("${SessionLabel}/${name}: Runtime world environment is not initialized")
+    }
+    if (($environmentOwnership.dayGroupDefinitionCount -le 0) -or
+        ($environmentOwnership.activeDayGroupCount -ne 1)) {
+        $failures.Add((
+            "${SessionLabel}/${name}: Runtime environment ownership is {0}/{1}, expected definitions with one active group" -f
+                $environmentOwnership.dayGroupDefinitionCount,
+                $environmentOwnership.activeDayGroupCount))
+    }
+    foreach ($field in @(
+        'bufferedTeleportDestinationCount',
+        'pendingTeleportStartCount',
+        'activeTeleportCount',
+        'acceptedTeleportDestinationCount',
+        'activeRevealCount',
+        'pendingDestinationReadinessCount',
+        'hostProjectionCount',
+        'pendingHostAcknowledgementCount')) {
+        if ([int]$transitOwnership.$field -ne 0) {
+            $failures.Add((
+                "${SessionLabel}/${name}: transitOwnership.$field={0}, expected zero at a stable checkpoint" -f
+                    $transitOwnership.$field))
+        }
+    }
     if ($resources.pendingLiveTeardowns -ne 0) {
         $failures.Add("${SessionLabel}/${name}: $($resources.pendingLiveTeardowns) live teardown(s) pending")
     }