diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index e1e3e1b..e2b62d9 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -5133,6 +5133,7 @@ public sealed class GameWindow : IDisposable
                 Position = e.Position + worldOffset,
                 Rotation = e.Rotation,
                 MeshRefs = meshRefs,
+                IsBuildingShell = e.IsBuildingShell,  // Phase A8: preserve dat-level tag
             };
             hydrated.Add(entity);
         }
diff --git a/src/AcDream.Core/World/LandblockLoader.cs b/src/AcDream.Core/World/LandblockLoader.cs
index b18608a..c685496 100644
--- a/src/AcDream.Core/World/LandblockLoader.cs
+++ b/src/AcDream.Core/World/LandblockLoader.cs
@@ -82,6 +82,7 @@ public static class LandblockLoader
                 Position = building.Frame.Origin,
                 Rotation = building.Frame.Orientation,
                 MeshRefs = Array.Empty<MeshRef>(),
+                IsBuildingShell = true,  // Phase A8: tag at source array boundary
             };
             buildingEntity.RefreshAabb(); // A.5 T18: populate cached AABB at construction
             result.Add(buildingEntity);
diff --git a/src/AcDream.Core/World/WorldEntity.cs b/src/AcDream.Core/World/WorldEntity.cs
index 20643d3..0a70d81 100644
--- a/src/AcDream.Core/World/WorldEntity.cs
+++ b/src/AcDream.Core/World/WorldEntity.cs
@@ -44,6 +44,25 @@ public sealed class WorldEntity
     /// </summary>
     public uint? ParentCellId { get; init; }
 
+    /// <summary>
+    /// True when this entity originates from <c>LandBlockInfo.Buildings[]</c>
+    /// (the dat array that carries building shells: cottage walls, smithy walls,
+    /// inn walls — every solid building enclosure). False for entities from
+    /// <c>LandBlockInfo.Objects[]</c> (rocks, fences, lampposts, tree clusters —
+    /// outdoor scenery placeholders). The two arrays are conflated through
+    /// hydration today but the dat itself carries the distinction; retail
+    /// (<c>CLandBlock::init_buildings</c>) and WorldBuilder
+    /// (<c>SceneryInstance.IsBuilding</c>) both preserve it.
+    ///
+    /// <para>
+    /// Read at draw time by <c>WbDrawDispatcher</c>'s <c>IndoorPass</c>
+    /// partition so building shells render unconditionally when the camera
+    /// is inside their building (they ARE the indoor walls), not stencil-gated
+    /// as outdoor scenery would be.
+    /// </para>
+    /// </summary>
+    public bool IsBuildingShell { get; init; }
+
     /// <summary>
     /// Uniform scale applied to this entity's mesh by the scenery pipeline.
     /// For scenery objects this is spawn.Scale (typically 0.8–1.3). For stabs
diff --git a/tests/AcDream.Core.Tests/World/LandblockLoaderTests.cs b/tests/AcDream.Core.Tests/World/LandblockLoaderTests.cs
index d1d24b8..21096dd 100644
--- a/tests/AcDream.Core.Tests/World/LandblockLoaderTests.cs
+++ b/tests/AcDream.Core.Tests/World/LandblockLoaderTests.cs
@@ -162,4 +162,54 @@ public class LandblockLoaderTests
         Assert.Single(entities);
         Assert.Equal(1u, entities[0].Id);
     }
+
+    [Fact]
+    public void BuildEntitiesFromInfo_TagsBuildingsWithIsBuildingShellTrue()
+    {
+        var info = new LandBlockInfo
+        {
+            Buildings =
+            {
+                new BuildingInfo
+                {
+                    ModelId = 0x02000123u,  // Setup id
+                    Frame = new Frame
+                    {
+                        Origin = new Vector3(10f, 20f, 30f),
+                        Orientation = Quaternion.Identity,
+                    },
+                },
+            },
+        };
+
+        var entities = LandblockLoader.BuildEntitiesFromInfo(info);
+
+        Assert.Single(entities);
+        Assert.True(entities[0].IsBuildingShell);
+    }
+
+    [Fact]
+    public void BuildEntitiesFromInfo_TagsObjectsWithIsBuildingShellFalse()
+    {
+        var info = new LandBlockInfo
+        {
+            Objects =
+            {
+                new Stab
+                {
+                    Id = 0x01000123u,  // GfxObj id
+                    Frame = new Frame
+                    {
+                        Origin = new Vector3(10f, 20f, 30f),
+                        Orientation = Quaternion.Identity,
+                    },
+                },
+            },
+        };
+
+        var entities = LandblockLoader.BuildEntitiesFromInfo(info);
+
+        Assert.Single(entities);
+        Assert.False(entities[0].IsBuildingShell);
+    }
 }