refactor(streaming): capture landblock build origin

src/AcDream.App/Rendering/GameWindow.cs

@@ -2491,8 +2491,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         // buildMeshOrNull (T12) receives the already-loaded LoadedLandblock so
         // it can call LandblockMesh.Build without a dat read — _heightTable and
         // _blendCtx are read-only after init, _surfaceCache is ConcurrentDictionary (T9).
-        _streamer = new AcDream.App.Streaming.LandblockStreamer(
-            loadLandblock: (id, kind) => BuildLandblockForStreaming(id, kind),
+        _streamer = AcDream.App.Streaming.LandblockStreamer.CreateForRequests(
+            loadLandblock: BuildLandblockForStreaming,
             buildMeshOrNull: (id, lb) =>
             {
                 if (lb is null || _heightTable is null || _blendCtx is null || _surfaceCache is null)
@@ -2508,7 +2508,14 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         _streamer.Start();
 
         _streamingController = new AcDream.App.Streaming.StreamingController(
-            enqueueLoad: (id, kind, generation) => _streamer.EnqueueLoad(id, kind, generation),
+            enqueueLoad: (id, kind, generation) => _streamer.EnqueueLoad(
+                new AcDream.App.Streaming.LandblockBuildRequest(
+                    id,
+                    kind,
+                    generation,
+                    new AcDream.App.Streaming.LandblockBuildOrigin(
+                        _liveCenterX,
+                        _liveCenterY))),
             enqueueUnload: (id, generation) => _streamer.EnqueueUnload(id, generation),
             drainCompletions: _streamer.DrainCompletions,
             applyTerrain:     ApplyLoadedTerrain,
@@ -3792,8 +3799,7 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
     /// early-out at the source.
     /// </summary>
     private AcDream.App.Streaming.LandblockBuild? BuildLandblockForStreaming(
-        uint landblockId,
-        AcDream.App.Streaming.LandblockStreamJobKind kind)
+        AcDream.App.Streaming.LandblockBuildRequest request)
     {
         if (_dats is null) return null;
 
@@ -3816,31 +3822,31 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
             {
                 long waitedMs = sw.ElapsedMilliseconds;
                 sw.Restart();
-                var built = BuildLandblockForStreamingLocked(landblockId, kind);
+                var built = BuildLandblockForStreamingLocked(request);
                 AcDream.Core.Physics.PhysicsDiagnostics.LogTeleport(
-                    "BUILD", landblockId,
-                    $"waited={waitedMs}ms held={sw.ElapsedMilliseconds}ms kind={kind}");
+                    "BUILD", request.LandblockId,
+                    $"waited={waitedMs}ms held={sw.ElapsedMilliseconds}ms kind={request.Kind}");
                 return built;
             }
         }
         lock (_datLock)
         {
-            return BuildLandblockForStreamingLocked(landblockId, kind);
+            return BuildLandblockForStreamingLocked(request);
         }
     }
 
     private AcDream.App.Streaming.LandblockBuild? BuildLandblockForStreamingLocked(
-        uint landblockId,
-        AcDream.App.Streaming.LandblockStreamJobKind kind)
+        AcDream.App.Streaming.LandblockBuildRequest request)
     {
         if (_dats is null) return null;
+        uint landblockId = request.LandblockId;
 
         // ISSUE #54: far-tier early-out — heightmap only, empty entities.
         // Skips the LandBlockInfo dat read AND all entity hydration (stabs
         // + buildings) AND the SceneryGenerator AND interior cells. Cuts
         // worker-thread cost per far-tier LB from ~tens of ms to a single
         // dat read.
-        if (kind == AcDream.App.Streaming.LandblockStreamJobKind.LoadFar)
+        if (request.Kind == AcDream.App.Streaming.LandblockStreamJobKind.LoadFar)
         {
             var heightmapOnly = _dats.Get<DatReaderWriter.DBObjs.LandBlock>(landblockId);
             if (heightmapOnly is null) return null;
@@ -3849,7 +3855,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
                     landblockId,
                     heightmapOnly,
                     System.Array.Empty<AcDream.Core.World.WorldEntity>(),
-                    AcDream.Core.World.PhysicsDatBundle.Empty));   // far tier: no cells/buildings/entities
+                    AcDream.Core.World.PhysicsDatBundle.Empty),
+                Origin: request.Origin);   // far tier: no cells/buildings/entities
         }
 
         var baseLoaded = AcDream.Core.World.LandblockLoader.Load(_dats, landblockId);
@@ -3858,8 +3865,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         int lbX = (int)((landblockId >> 24) & 0xFFu);
         int lbY = (int)((landblockId >> 16) & 0xFFu);
         var worldOffset = new System.Numerics.Vector3(
-            (lbX - _liveCenterX) * 192f,
-            (lbY - _liveCenterY) * 192f,
+            (lbX - request.Origin.CenterX) * 192f,
+            (lbY - request.Origin.CenterY) * 192f,
             0f);
 
         // Hydrate the stabs: same logic as the old OnLoad preload. Each stab
@@ -3926,9 +3933,18 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
 
         // Task 8: merge stabs + scenery + interior into one entity list.
         var merged = new List<AcDream.Core.World.WorldEntity>(hydrated);
-        merged.AddRange(BuildSceneryEntitiesForStreaming(baseLoaded, lbX, lbY));
+        merged.AddRange(BuildSceneryEntitiesForStreaming(
+            baseLoaded,
+            lbX,
+            lbY,
+            request.Origin));
         var envCellBuild = new AcDream.App.Rendering.Wb.EnvCellLandblockBuildBuilder(landblockId);
-        merged.AddRange(BuildInteriorEntitiesForStreaming(landblockId, lbX, lbY, envCellBuild));
+        merged.AddRange(BuildInteriorEntitiesForStreaming(
+            landblockId,
+            lbX,
+            lbY,
+            request.Origin,
+            envCellBuild));
 
         // datLock fix: pre-read (under the worker's _datLock) every dat the apply
         // consumes, so ApplyLoadedTerrainLocked can run lock-free. Built AFTER
@@ -3941,7 +3957,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
                 baseLoaded.Heightmap,
                 merged,
                 physicsDats),
-            completedEnvCells);
+            completedEnvCells,
+            request.Origin);
     }
 
     private void EnsureEnvCellMeshesAfterPin(
@@ -4036,7 +4053,10 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
     /// LoadedLandblock instead of iterating worldView.Landblocks.
     /// </summary>
     private List<AcDream.Core.World.WorldEntity> BuildSceneryEntitiesForStreaming(
-        AcDream.Core.World.LoadedLandblock lb, int lbX, int lbY)
+        AcDream.Core.World.LoadedLandblock lb,
+        int lbX,
+        int lbY,
+        AcDream.App.Streaming.LandblockBuildOrigin origin)
     {
         var result = new List<AcDream.Core.World.WorldEntity>();
         if (_dats is null || _heightTable is null) return result;
@@ -4069,8 +4089,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         if (spawns.Count == 0) return result;
 
         var lbOffset = new System.Numerics.Vector3(
-            (lbX - _liveCenterX) * 192f,
-            (lbY - _liveCenterY) * 192f,
+            (lbX - origin.CenterX) * 192f,
+            (lbY - origin.CenterY) * 192f,
             0f);
 
         // Per-landblock id namespace. The top nibble identifies procedural
@@ -4265,6 +4285,7 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         uint landblockId,
         int lbX,
         int lbY,
+        AcDream.App.Streaming.LandblockBuildOrigin origin,
         AcDream.App.Rendering.Wb.EnvCellLandblockBuildBuilder envCellBuild)
     {
         var result = new List<AcDream.Core.World.WorldEntity>();
@@ -4274,8 +4295,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         if (lbInfo is null || lbInfo.NumCells == 0) return result;
 
         var lbOffset = new System.Numerics.Vector3(
-            (lbX - _liveCenterX) * 192f,
-            (lbY - _liveCenterY) * 192f,
+            (lbX - origin.CenterX) * 192f,
+            (lbY - origin.CenterY) * 192f,
             0f);
 
         // Per-landblock id namespace — see AcDream.Core.World.InteriorEntityIdAllocator
@@ -4654,8 +4675,8 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
         int lbX = (int)lbXu;
         int lbY = (int)lbYu;
         var origin = new System.Numerics.Vector3(
-            (lbX - _liveCenterX) * 192f,
-            (lbY - _liveCenterY) * 192f,
+            (lbX - build.Origin.CenterX) * 192f,
+            (lbY - build.Origin.CenterY) * 192f,
             0f);
 
         // Phase A.5 T15/T16: route through AddLandblockWithMesh — the named
@@ -4820,7 +4841,7 @@ public sealed class GameWindow : IDisposable, ILiveAnimationPresentationContext
             {
                 // #146 (2026-06-24): clear this landblock's prior building cache so
                 // the loop re-bases each building's STREAMING-RELATIVE WorldTransform
-                // with the CURRENT _liveCenter (origin, recomputed above per apply).
+                // with this completion's captured origin (recomputed above per apply).
                 // CacheBuilding's per-cell first-wins then applies fresh within this
                 // pass — mirrors terrain's per-apply WorldOffset re-base (AddLandblock).
                 // Without it, CacheBuilding's idempotent guard locks the transform at

src/AcDream.App/Streaming/LandblockBuild.cs

@@ -10,7 +10,8 @@ namespace AcDream.App.Streaming;
 /// </summary>
 public sealed record LandblockBuild(
     LoadedLandblock Landblock,
-    EnvCellLandblockBuild? EnvCells = null)
+    EnvCellLandblockBuild? EnvCells = null,
+    LandblockBuildOrigin Origin = default)
 {
     public uint LandblockId => Landblock.LandblockId;
 }

src/AcDream.App/Streaming/LandblockBuildRequest.cs

@@ -0,0 +1,36 @@
+namespace AcDream.App.Streaming;
+
+/// <summary>
+/// Immutable world-origin center captured by the update thread when a
+/// landblock load is admitted. Worker construction and render publication use
+/// this same value, so a later recenter cannot combine two coordinate frames.
+/// </summary>
+public readonly record struct LandblockBuildOrigin
+{
+    public LandblockBuildOrigin(int centerX, int centerY)
+    {
+        CenterX = centerX;
+        CenterY = centerY;
+        IsSpecified = true;
+    }
+
+    public int CenterX { get; }
+    public int CenterY { get; }
+
+    /// <summary>
+    /// Distinguishes a captured origin at the valid map coordinate (0,0)
+    /// from an old compatibility request that carries no origin at all.
+    /// </summary>
+    public bool IsSpecified { get; }
+}
+
+/// <summary>
+/// Complete immutable input to one CPU-side landblock build.
+/// <see cref="Generation"/> is carried for matching and diagnostics only;
+/// residency policy remains owned by <see cref="StreamingController"/>.
+/// </summary>
+public readonly record struct LandblockBuildRequest(
+    uint LandblockId,
+    LandblockStreamJobKind Kind,
+    ulong Generation,
+    LandblockBuildOrigin Origin);

src/AcDream.App/Streaming/LandblockPresentationPipeline.cs

@@ -161,7 +161,9 @@ public sealed class LandblockPresentationPipeline
             transaction = new PublicationTransaction
             {
                 Kind = PublicationKind.Far,
-                Build = new LandblockBuild(farLandblock),
+                Build = new LandblockBuild(
+                    farLandblock,
+                    Origin: completedBuild.Origin),
                 MeshData = meshData,
                 LandblockId = farLandblock.LandblockId,
                 Tier = LandblockStreamTier.Far,

src/AcDream.App/Streaming/LandblockStreamJob.cs

@@ -15,7 +15,12 @@ public abstract record LandblockStreamJob(uint LandblockId)
     public sealed record Load(
         uint LandblockId,
         LandblockStreamJobKind Kind,
-        ulong Generation = 0) : LandblockStreamJob(LandblockId);
+        ulong Generation = 0,
+        LandblockBuildOrigin Origin = default) : LandblockStreamJob(LandblockId)
+    {
+        public LandblockBuildRequest Request =>
+            new(LandblockId, Kind, Generation, Origin);
+    }
     public sealed record Unload(
         uint LandblockId,
         ulong Generation = 0) : LandblockStreamJob(LandblockId);

src/AcDream.App/Streaming/LandblockStreamer.cs

@@ -52,7 +52,8 @@ public sealed class LandblockStreamer : IDisposable
     /// </summary>
     public const int DefaultDrainBatchSize = 4;
 
-    private readonly Func<uint, LandblockStreamJobKind, LandblockBuild?> _loadLandblock;
+    private readonly Func<LandblockBuildRequest, LandblockBuild?> _loadLandblock;
+    private readonly bool _supportsRequestOrigin;
     private readonly Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?> _buildMeshOrNull;
     private readonly Channel<LandblockStreamJob> _inbox;
     private readonly Channel<LandblockStreamResult> _outbox;
@@ -65,17 +66,17 @@ public sealed class LandblockStreamer : IDisposable
     private bool _disposeCompleted;
 
     /// <summary>
-    /// Primary ctor — the factory takes the job's <see cref="LandblockStreamJobKind"/>
-    /// so it can branch on far-tier vs near-tier and skip entity hydration on far-tier
-    /// loads (heightmap-only). See ISSUE #54: prior to this signature the worker always
-    /// called the full-load path and stripped entities at the output, wasting per-LB
-    /// <c>LandBlockInfo</c> + <c>SceneryGenerator</c> work.
+    /// Primary constructor. The factory receives the complete immutable
+    /// request, including job kind and enqueue-time world origin. ISSUE #54
+    /// uses the kind to skip entity hydration for heightmap-only far loads.
     /// </summary>
-    public LandblockStreamer(
-        Func<uint, LandblockStreamJobKind, LandblockBuild?> loadLandblock,
-        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
+    private LandblockStreamer(
+        Func<LandblockBuildRequest, LandblockBuild?> loadLandblock,
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull,
+        bool supportsRequestOrigin)
     {
         _loadLandblock = loadLandblock;
+        _supportsRequestOrigin = supportsRequestOrigin;
         // Default: no mesh build (returns null → Failed result). Production
         // wires in LandblockMesh.Build via the T12 construction site.
         _buildMeshOrNull = buildMeshOrNull ?? ((_, _) => null);
@@ -85,6 +86,32 @@ public sealed class LandblockStreamer : IDisposable
             new UnboundedChannelOptions { SingleReader = true, SingleWriter = true });
     }
 
+    /// <summary>
+    /// Creates the request-aware production streamer. A named factory keeps
+    /// legacy one-parameter loader lambdas source-compatible without an
+    /// ambiguous constructor overload.
+    /// </summary>
+    public static LandblockStreamer CreateForRequests(
+        Func<LandblockBuildRequest, LandblockBuild?> loadLandblock,
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null) =>
+        new(loadLandblock, buildMeshOrNull, supportsRequestOrigin: true);
+
+    /// <summary>
+    /// Compatibility constructor for build factories that predate the
+    /// immutable request/origin seam.
+    /// </summary>
+    public LandblockStreamer(
+        Func<uint, LandblockStreamJobKind, LandblockBuild?> loadLandblock,
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
+        : this(
+            request => loadLandblock(request.LandblockId, request.Kind) is { } build
+                ? build
+                : null,
+            buildMeshOrNull,
+            supportsRequestOrigin: false)
+    {
+    }
+
     /// <summary>
     /// Compatibility constructor for loaders that have no App-owned cell payload.
     /// Production uses the <see cref="LandblockBuild"/> overload so render state
@@ -94,10 +121,11 @@ public sealed class LandblockStreamer : IDisposable
         Func<uint, LandblockStreamJobKind, LoadedLandblock?> loadLandblock,
         Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
         : this(
-            (id, kind) => loadLandblock(id, kind) is { } landblock
-                ? new LandblockBuild(landblock)
+            request => loadLandblock(request.LandblockId, request.Kind) is { } landblock
+                ? new LandblockBuild(landblock, Origin: request.Origin)
                 : null,
-            buildMeshOrNull)
+            buildMeshOrNull,
+            supportsRequestOrigin: false)
     {
     }
 
@@ -105,16 +133,17 @@ public sealed class LandblockStreamer : IDisposable
     /// Back-compat overload — wraps a kind-agnostic factory so existing test code
     /// that doesn't care about the JobKind branch keeps compiling. The wrapper
     /// ignores the kind and calls the factory once per LB regardless of tier.
-    /// New production code should use the primary 2-arg ctor.
+    /// New production code should use <see cref="CreateForRequests"/>.
     /// </summary>
     public LandblockStreamer(
         Func<uint, LoadedLandblock?> loadLandblock,
         Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
         : this(
-            (id, _) => loadLandblock(id) is { } landblock
-                ? new LandblockBuild(landblock)
+            request => loadLandblock(request.LandblockId) is { } landblock
+                ? new LandblockBuild(landblock, Origin: request.Origin)
                 : null,
-            buildMeshOrNull)
+            buildMeshOrNull,
+            supportsRequestOrigin: false)
     {
     }
 
@@ -152,11 +181,47 @@ public sealed class LandblockStreamer : IDisposable
         uint landblockId,
         LandblockStreamJobKind kind = LandblockStreamJobKind.LoadNear,
         ulong generation = 0)
+    {
+        if (_supportsRequestOrigin)
+        {
+            throw new InvalidOperationException(
+                "Request-aware landblock loaders require an explicit captured origin.");
+        }
+        EnqueueLoad(new LandblockBuildRequest(
+            landblockId,
+            kind,
+            generation,
+            default));
+    }
+
+    /// <summary>
+    /// Non-blocking enqueue of the exact request captured by the update
+    /// thread. The worker and completion retain its origin unchanged.
+    /// </summary>
+    public void EnqueueLoad(LandblockBuildRequest request)
     {
         if (System.Threading.Volatile.Read(ref _disposed) != 0)
             throw new ObjectDisposedException(nameof(LandblockStreamer));
-        AcDream.Core.Physics.PhysicsDiagnostics.LogTeleport("ENQ", landblockId, $"kind={kind}");
-        WriteJob(new LandblockStreamJob.Load(landblockId, kind, generation));
+        if (_supportsRequestOrigin && !request.Origin.IsSpecified)
+        {
+            throw new InvalidOperationException(
+                "Request-aware landblock loaders require a specified captured origin.");
+        }
+        if (!_supportsRequestOrigin && request.Origin.IsSpecified)
+        {
+            throw new InvalidOperationException(
+                "This compatibility landblock loader cannot consume a non-default build origin. " +
+                "Use LandblockStreamer.CreateForRequests.");
+        }
+        AcDream.Core.Physics.PhysicsDiagnostics.LogTeleport(
+            "ENQ",
+            request.LandblockId,
+            $"kind={request.Kind} origin=({request.Origin.CenterX:X2},{request.Origin.CenterY:X2})");
+        WriteJob(new LandblockStreamJob.Load(
+            request.LandblockId,
+            request.Kind,
+            request.Generation,
+            request.Origin));
     }
 
     /// <summary>
@@ -358,13 +423,21 @@ public sealed class LandblockStreamer : IDisposable
                 // factory returns far-tier with entities anyway.
                 try
                 {
-                    var build = _loadLandblock(load.LandblockId, load.Kind);
+                    var build = _loadLandblock(load.Request);
                     if (build is null)
                     {
                         _outbox.Writer.TryWrite(new LandblockStreamResult.Failed(
                             load.LandblockId, "LandblockLoader.Load returned null", load.Generation));
                         break;
                     }
+                    if (build.Origin != load.Origin)
+                    {
+                        _outbox.Writer.TryWrite(new LandblockStreamResult.Failed(
+                            load.LandblockId,
+                            $"Landblock build origin {build.Origin} did not match request origin {load.Origin}",
+                            load.Generation));
+                        break;
+                    }
                     var lb = build.Landblock;
                     if (load.Kind == LandblockStreamJobKind.PromoteToNear)
                     {
@@ -388,18 +461,29 @@ public sealed class LandblockStreamer : IDisposable
                     }
                     var tier = load.Kind == LandblockStreamJobKind.LoadFar
                         ? LandblockStreamTier.Far : LandblockStreamTier.Near;
-                    if (tier == LandblockStreamTier.Far && lb.Entities.Count > 0)
+                    if (tier == LandblockStreamTier.Far)
                     {
                         // Belt-and-suspenders: factory should have skipped
                         // entity hydration for LoadFar. If it didn't, fail
                         // loud in Debug builds and strip in Release.
-                        System.Diagnostics.Debug.Assert(false,
-                            $"Far-tier factory should skip entity hydration; got {lb.Entities.Count} entities for LB 0x{load.LandblockId:X8}");
+                        bool hasNearPayload =
+                            lb.Entities.Count > 0 ||
+                            build.EnvCells is not null ||
+                            lb.PhysicsDats is { } physicsDats &&
+                            (physicsDats.Info is not null ||
+                             physicsDats.EnvCells.Count > 0 ||
+                             physicsDats.Environments.Count > 0 ||
+                             physicsDats.Setups.Count > 0 ||
+                             physicsDats.GfxObjs.Count > 0);
+                        System.Diagnostics.Debug.Assert(
+                            !hasNearPayload,
+                            $"Far-tier factory returned Near payload for LB 0x{load.LandblockId:X8}");
                         lb = new LoadedLandblock(
                             lb.LandblockId,
                             lb.Heightmap,
-                            System.Array.Empty<AcDream.Core.World.WorldEntity>());
-                        build = new LandblockBuild(lb);
+                            System.Array.Empty<AcDream.Core.World.WorldEntity>(),
+                            PhysicsDatBundle.Empty);
+                        build = new LandblockBuild(lb, Origin: build.Origin);
                     }
                     _outbox.Writer.TryWrite(new LandblockStreamResult.Loaded(
                         load.LandblockId, tier, build, mesh, load.Generation));

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

@@ -0,0 +1,314 @@
+using AcDream.App.Rendering.Wb;
+using AcDream.App.Streaming;
+using AcDream.Core.Terrain;
+using AcDream.Core.World;
+using DatReaderWriter.DBObjs;
+
+namespace AcDream.App.Tests.Streaming;
+
+public sealed class LandblockBuildOriginTests
+{
+    private const int SpinTimeoutMs = 2000;
+    private const int SpinStepMs = 10;
+
+    [Fact]
+    public void ExplicitMapZeroOrigin_IsDistinctFromUnspecifiedCompatibilityOrigin()
+    {
+        var mapZero = new LandblockBuildOrigin(0, 0);
+
+        Assert.True(mapZero.IsSpecified);
+        Assert.False(default(LandblockBuildOrigin).IsSpecified);
+        Assert.NotEqual(default, mapZero);
+    }
+
+    [Fact]
+    public async Task RequestAwareLoad_CarriesExplicitMapZeroOriginThroughFactoryAndCompletion()
+    {
+        const uint landblockId = 0x0000FFFFu;
+        var capturedOrigin = new LandblockBuildOrigin(0, 0);
+        LandblockBuildRequest? observedRequest = null;
+
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request =>
+            {
+                observedRequest = request;
+                return EmptyBuild(request.LandblockId, request.Origin);
+            },
+            buildMeshOrNull: (_, _) => EmptyMesh());
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            landblockId,
+            LandblockStreamJobKind.LoadNear,
+            Generation: 77,
+            capturedOrigin));
+        streamer.Start();
+
+        var loaded = Assert.IsType<LandblockStreamResult.Loaded>(
+            await DrainFirstAsync(streamer));
+
+        Assert.Equal(
+            new LandblockBuildRequest(
+                landblockId,
+                LandblockStreamJobKind.LoadNear,
+                77,
+                capturedOrigin),
+            observedRequest);
+        Assert.Equal(capturedOrigin, loaded.Build.Origin);
+        Assert.Equal(77ul, loaded.Generation);
+    }
+
+    [Fact]
+    public async Task RequestAwareLoad_WhenFactoryReturnsUnspecifiedOrigin_FailsAtMapZero()
+    {
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request => EmptyBuild(request.LandblockId, default));
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            0x0000FFFFu,
+            LandblockStreamJobKind.LoadNear,
+            Generation: 78,
+            new LandblockBuildOrigin(0, 0)));
+        streamer.Start();
+
+        var failed = Assert.IsType<LandblockStreamResult.Failed>(
+            await DrainFirstAsync(streamer));
+
+        Assert.Contains("origin", failed.Error, StringComparison.OrdinalIgnoreCase);
+        Assert.Equal(78ul, failed.Generation);
+    }
+
+    [Fact]
+    public void CompatibilityLoader_RejectsEvenExplicitMapZeroOriginBeforeQueueing()
+    {
+        using var streamer = new LandblockStreamer(loadLandblock: _ => null);
+
+        Assert.Throws<InvalidOperationException>(() => streamer.EnqueueLoad(
+            new LandblockBuildRequest(
+                0x0000FFFFu,
+                LandblockStreamJobKind.LoadNear,
+                Generation: 79,
+                new LandblockBuildOrigin(0, 0))));
+    }
+
+    [Fact]
+    public void RequestAwareLoader_RejectsOriginlessCompatibilityEnqueue()
+    {
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request => EmptyBuild(request.LandblockId, request.Origin));
+
+        Assert.Throws<InvalidOperationException>(() =>
+            streamer.EnqueueLoad(0xA9B4FFFFu));
+    }
+
+    [Fact]
+    public void RequestAwareLoader_RejectsDirectRequestWithUnspecifiedOrigin()
+    {
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request => EmptyBuild(request.LandblockId, request.Origin));
+
+        Assert.Throws<InvalidOperationException>(() => streamer.EnqueueLoad(
+            new LandblockBuildRequest(
+                0xA9B4FFFFu,
+                LandblockStreamJobKind.LoadNear,
+                Generation: 80,
+                Origin: default)));
+    }
+
+    [Fact]
+    public async Task TwoQueuedLoads_RetainTheirDistinctOriginAndGeneration()
+    {
+        var observed = new List<LandblockBuildRequest>();
+        var firstOrigin = new LandblockBuildOrigin(0xA9, 0xB4);
+        var secondOrigin = new LandblockBuildOrigin(0x71, 0xEC);
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request =>
+            {
+                observed.Add(request);
+                return EmptyBuild(request.LandblockId, request.Origin);
+            },
+            buildMeshOrNull: (_, _) => EmptyMesh());
+
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            0xA9B4FFFFu,
+            LandblockStreamJobKind.LoadNear,
+            Generation: 80,
+            firstOrigin));
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            0x71ECFFFFu,
+            LandblockStreamJobKind.LoadNear,
+            Generation: 81,
+            secondOrigin));
+        streamer.Start();
+
+        IReadOnlyList<LandblockStreamResult> completions =
+            await DrainCountAsync(streamer, 2);
+
+        Assert.Equal([firstOrigin, secondOrigin], observed.Select(request => request.Origin));
+        Assert.Equal([80ul, 81ul], completions.Select(result => result.Generation));
+        Assert.Equal(
+            [firstOrigin, secondOrigin],
+            completions
+                .Cast<LandblockStreamResult.Loaded>()
+                .Select(result => result.Build.Origin));
+    }
+
+    [Fact]
+    public async Task QueuedPromotion_SupersedesOldFarWithItsOwnOriginAndGeneration()
+    {
+        var observed = new List<LandblockBuildRequest>();
+        var oldOrigin = new LandblockBuildOrigin(0xA9, 0xB4);
+        var newOrigin = new LandblockBuildOrigin(0x71, 0xEC);
+        const uint landblockId = 0x71ECFFFFu;
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request =>
+            {
+                observed.Add(request);
+                return EmptyBuild(request.LandblockId, request.Origin);
+            },
+            buildMeshOrNull: (_, _) => EmptyMesh());
+
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            landblockId,
+            LandblockStreamJobKind.LoadFar,
+            Generation: 82,
+            oldOrigin));
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            landblockId,
+            LandblockStreamJobKind.PromoteToNear,
+            Generation: 83,
+            newOrigin));
+        streamer.Start();
+
+        var promoted = Assert.IsType<LandblockStreamResult.Promoted>(
+            await DrainFirstAsync(streamer));
+
+        Assert.Equal([new LandblockBuildRequest(
+            landblockId,
+            LandblockStreamJobKind.PromoteToNear,
+            83,
+            newOrigin)], observed);
+        Assert.Equal(newOrigin, promoted.Build.Origin);
+        Assert.Equal(83ul, promoted.Generation);
+    }
+
+    [Fact]
+    public async Task FarLoad_StripsEnvCellsAndPhysicsEvenWhenEntityListIsAlreadyEmpty()
+    {
+        const uint landblockId = 0xA9B4FFFFu;
+        var origin = new LandblockBuildOrigin(0xA9, 0xB4);
+        var physics = new PhysicsDatBundle(
+            new LandBlockInfo(),
+            new Dictionary<uint, EnvCell>(),
+            new Dictionary<uint, DatReaderWriter.DBObjs.Environment>(),
+            new Dictionary<uint, Setup>(),
+            new Dictionary<uint, GfxObj>());
+        var envCells = new EnvCellLandblockBuild(
+            landblockId,
+            Array.Empty<AcDream.App.Rendering.LoadedCell>(),
+            Array.Empty<EnvCellShellPlacement>());
+        using var streamer = LandblockStreamer.CreateForRequests(
+            loadLandblock: request => new LandblockBuild(
+                new LoadedLandblock(
+                    request.LandblockId,
+                    new LandBlock(),
+                    Array.Empty<WorldEntity>(),
+                    physics),
+                envCells,
+                request.Origin),
+            buildMeshOrNull: (_, _) => EmptyMesh());
+        streamer.EnqueueLoad(new LandblockBuildRequest(
+            landblockId,
+            LandblockStreamJobKind.LoadFar,
+            Generation: 84,
+            origin));
+        streamer.Start();
+
+        var loaded = Assert.IsType<LandblockStreamResult.Loaded>(
+            await DrainFirstAsync(streamer));
+
+        Assert.Equal(LandblockStreamTier.Far, loaded.Tier);
+        Assert.Empty(loaded.Landblock.Entities);
+        Assert.Same(PhysicsDatBundle.Empty, loaded.Landblock.PhysicsDats);
+        Assert.Null(loaded.Build.EnvCells);
+        Assert.Equal(origin, loaded.Build.Origin);
+    }
+
+    [Fact]
+    public void GameWindowBuildAndPublication_UseCapturedOriginInsteadOfLiveCenter()
+    {
+        string root = FindRepoRoot();
+        string source = File.ReadAllText(Path.Combine(
+            root,
+            "src",
+            "AcDream.App",
+            "Rendering",
+            "GameWindow.cs"));
+        string buildSection = Slice(
+            source,
+            "private AcDream.App.Streaming.LandblockBuild? BuildLandblockForStreaming(",
+            "private void AdvanceLandblockPresentationRetirement(");
+        string publicationSection = Slice(
+            source,
+            "private void ApplyLoadedTerrainLocked(",
+            "private void OnUpdate(double dt)");
+
+        Assert.Contains("request.Origin", buildSection, StringComparison.Ordinal);
+        Assert.DoesNotContain("_liveCenterX", buildSection, StringComparison.Ordinal);
+        Assert.DoesNotContain("_liveCenterY", buildSection, StringComparison.Ordinal);
+        Assert.Contains("build.Origin.CenterX", publicationSection, StringComparison.Ordinal);
+        Assert.Contains("build.Origin.CenterY", publicationSection, StringComparison.Ordinal);
+        Assert.DoesNotContain("_liveCenterX", publicationSection, StringComparison.Ordinal);
+        Assert.DoesNotContain("_liveCenterY", publicationSection, StringComparison.Ordinal);
+    }
+
+    private static LandblockBuild EmptyBuild(uint landblockId, LandblockBuildOrigin origin) =>
+        new(
+            new LoadedLandblock(
+                landblockId,
+                new LandBlock(),
+                Array.Empty<WorldEntity>()),
+            Origin: origin);
+
+    private static LandblockMeshData EmptyMesh() =>
+        new(Array.Empty<TerrainVertex>(), Array.Empty<uint>());
+
+    private static async Task<LandblockStreamResult> DrainFirstAsync(
+        LandblockStreamer streamer) =>
+        (await DrainCountAsync(streamer, 1))[0];
+
+    private static async Task<IReadOnlyList<LandblockStreamResult>> DrainCountAsync(
+        LandblockStreamer streamer,
+        int count)
+    {
+        var results = new List<LandblockStreamResult>(count);
+        for (int i = 0; i < SpinTimeoutMs / SpinStepMs && results.Count < count; i++)
+        {
+            results.AddRange(streamer.DrainCompletions(count - results.Count));
+            if (results.Count < count)
+                await Task.Delay(SpinStepMs);
+        }
+
+        Assert.Equal(count, results.Count);
+        return results;
+    }
+
+    private static string Slice(string source, string startMarker, string endMarker)
+    {
+        int start = source.IndexOf(startMarker, StringComparison.Ordinal);
+        Assert.True(start >= 0, $"Missing source marker: {startMarker}");
+        int end = source.IndexOf(endMarker, start, StringComparison.Ordinal);
+        Assert.True(end > start, $"Missing source marker: {endMarker}");
+        return source[start..end];
+    }
+
+    private static string FindRepoRoot()
+    {
+        string? dir = AppContext.BaseDirectory;
+        while (dir is not null)
+        {
+            if (File.Exists(Path.Combine(dir, "AcDream.slnx")))
+                return dir;
+            dir = Directory.GetParent(dir)?.FullName;
+        }
+
+        throw new DirectoryNotFoundException("Could not locate AcDream.slnx.");
+    }
+}

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

@@ -100,7 +100,11 @@ public sealed class LandblockPresentationPipelineTests
     {
         const uint landblockId = 0x4040FFFFu;
         var state = new GpuWorldState();
-        LandblockBuild source = BuildWithShell(landblockId, Entity(9));
+        var origin = new LandblockBuildOrigin(0x40, 0x41);
+        LandblockBuild source = BuildWithShell(landblockId, Entity(9)) with
+        {
+            Origin = origin,
+        };
         LandblockBuild? published = null;
         int replayCount = 0;
         int recoveryCount = 0;
@@ -121,6 +125,7 @@ public sealed class LandblockPresentationPipelineTests
         Assert.Empty(published.Landblock.Entities);
         Assert.Same(PhysicsDatBundle.Empty, published.Landblock.PhysicsDats);
         Assert.Null(published.EnvCells);
+        Assert.Equal(origin, published.Origin);
         Assert.True(state.IsLoaded(landblockId));
         Assert.False(state.IsNearTier(landblockId));
         Assert.Equal(0, replayCount);