diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index 2ea6f5d..c3bba03 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -1612,7 +1612,14 @@ public sealed class GameWindow : IDisposable
             var wbEntitySpawnAdapter = new AcDream.App.Rendering.Wb.EntitySpawnAdapter(
                 _textureCache!, SequencerFactory, _wbMeshAdapter!);
             _wbEntitySpawnAdapter = wbEntitySpawnAdapter;
-            _worldState = new AcDream.App.Streaming.GpuWorldState(wbSpawnAdapter, wbEntitySpawnAdapter);
+            // Phase Post-A.5 #53 (Task 12): wire EntityClassificationCache.InvalidateLandblock
+            // so Tier 1 cache entries get swept on LB demote (Near to Far) and unload.
+            // Per spec §5.3 W3b. The callback receives the canonical landblock id
+            // matching the LandblockHint stored at Populate time.
+            _worldState = new AcDream.App.Streaming.GpuWorldState(
+                wbSpawnAdapter,
+                wbEntitySpawnAdapter,
+                onLandblockUnloaded: _classificationCache.InvalidateLandblock);
 
             _wbDrawDispatcher = new AcDream.App.Rendering.Wb.WbDrawDispatcher(
                 _gl, _meshShader!, _textureCache!, _wbMeshAdapter!, _wbEntitySpawnAdapter, _bindlessSupport!,
diff --git a/src/AcDream.App/Streaming/GpuWorldState.cs b/src/AcDream.App/Streaming/GpuWorldState.cs
index b0ad321..2965b24 100644
--- a/src/AcDream.App/Streaming/GpuWorldState.cs
+++ b/src/AcDream.App/Streaming/GpuWorldState.cs
@@ -42,12 +42,26 @@ public sealed class GpuWorldState
     private readonly LandblockSpawnAdapter? _wbSpawnAdapter;
     private readonly EntitySpawnAdapter? _wbEntitySpawnAdapter;
 
+    /// <summary>
+    /// Phase Post-A.5 #53 (Task 12): optional callback fired before
+    /// <see cref="RemoveEntitiesFromLandblock"/> zeroes a landblock's entity
+    /// list. Wired by <c>GameWindow</c> to
+    /// <c>EntityClassificationCache.InvalidateLandblock</c> so Tier 1 cache
+    /// entries get swept on LB demote (Near to Far) and unload. Receives
+    /// the canonicalized landblock id (low 16 bits forced to <c>0xFFFF</c>),
+    /// matching the <c>LandblockHint</c> stored at <c>Populate</c> time.
+    /// Null when the cache isn't relevant (tests).
+    /// </summary>
+    private readonly System.Action<uint>? _onLandblockUnloaded;
+
     public GpuWorldState(
         LandblockSpawnAdapter? wbSpawnAdapter = null,
-        EntitySpawnAdapter? wbEntitySpawnAdapter = null)
+        EntitySpawnAdapter? wbEntitySpawnAdapter = null,
+        System.Action<uint>? onLandblockUnloaded = null)
     {
         _wbSpawnAdapter = wbSpawnAdapter;
         _wbEntitySpawnAdapter = wbEntitySpawnAdapter;
+        _onLandblockUnloaded = onLandblockUnloaded;
     }
 
     private readonly Dictionary<uint, LoadedLandblock> _loaded = new();
@@ -380,6 +394,14 @@ public sealed class GpuWorldState
         if (!_loaded.TryGetValue(canonical, out var lb)) return;
         if (_wbSpawnAdapter is not null)
             _wbSpawnAdapter.OnLandblockUnloaded(canonical);
+
+        // Phase Post-A.5 #53 (Task 12): invalidate the EntityClassificationCache
+        // for this landblock BEFORE we drop the entity list. The cache stores
+        // canonical landblock ids (the dispatcher's _walkScratch carries
+        // entry.LandblockId from GpuWorldState.LandblockEntries, whose keys are
+        // canonicalized). Null when the cache isn't wired (tests). Per spec §5.3 W3b.
+        _onLandblockUnloaded?.Invoke(canonical);
+
         _loaded[canonical] = new LoadedLandblock(lb.LandblockId, lb.Heightmap, System.Array.Empty<WorldEntity>());
         _pendingByLandblock.Remove(canonical);
         RebuildFlatView();
diff --git a/tests/AcDream.Core.Tests/Streaming/GpuWorldStateTwoTierTests.cs b/tests/AcDream.Core.Tests/Streaming/GpuWorldStateTwoTierTests.cs
index 11ab0c5..24950fd 100644
--- a/tests/AcDream.Core.Tests/Streaming/GpuWorldStateTwoTierTests.cs
+++ b/tests/AcDream.Core.Tests/Streaming/GpuWorldStateTwoTierTests.cs
@@ -73,4 +73,53 @@ public class GpuWorldStateTwoTierTests
         state.AddLandblock(MakeStubLandblock(0xAAAAFFFFu));
         Assert.Equal(2, state.Entities.Count);
     }
+
+    /// <summary>
+    /// Phase Post-A.5 #53 (Task 12): the optional <c>onLandblockUnloaded</c>
+    /// callback fires once when <see cref="GpuWorldState.RemoveEntitiesFromLandblock"/>
+    /// drops a landblock's entity list, and is passed the canonicalized
+    /// landblock id (matching the <c>LandblockHint</c> the cache stored at
+    /// <c>Populate</c> time).
+    /// </summary>
+    [Fact]
+    public void RemoveEntitiesFromLandblock_FiresUnloadCallbackWithCanonicalId()
+    {
+        uint? observed = null;
+        int callCount = 0;
+        var state = new GpuWorldState(
+            wbSpawnAdapter: null,
+            wbEntitySpawnAdapter: null,
+            onLandblockUnloaded: id => { observed = id; callCount++; });
+
+        state.AddLandblock(MakeStubLandblock(0xA9B4FFFFu, MakeStubEntity(1)));
+
+        // Pass a cell-resolved id (low 16 bits non-FFFF) — the callback must
+        // receive the canonical (0xFFFF-tail) form, matching what the
+        // dispatcher's _walkScratch carries from GpuWorldState.LandblockEntries.
+        state.RemoveEntitiesFromLandblock(0xA9B40042u);
+
+        Assert.Equal(1, callCount);
+        Assert.Equal(0xA9B4FFFFu, observed);
+        Assert.Empty(state.Entities);
+    }
+
+    /// <summary>
+    /// Phase Post-A.5 #53 (Task 12): the callback must NOT fire when the
+    /// landblock isn't loaded — early return path. Symmetric with the
+    /// existing <c>_wbSpawnAdapter.OnLandblockUnloaded</c> guard.
+    /// </summary>
+    [Fact]
+    public void RemoveEntitiesFromLandblock_NotLoaded_DoesNotFireCallback()
+    {
+        int callCount = 0;
+        var state = new GpuWorldState(
+            wbSpawnAdapter: null,
+            wbEntitySpawnAdapter: null,
+            onLandblockUnloaded: _ => callCount++);
+
+        // Landblock never loaded.
+        state.RemoveEntitiesFromLandblock(0xA9B4FFFFu);
+
+        Assert.Equal(0, callCount);
+    }
 }