diff --git a/src/AcDream.App/Rendering/CellVisibility.cs b/src/AcDream.App/Rendering/CellVisibility.cs
index 87fdc67..d3cf6f1 100644
--- a/src/AcDream.App/Rendering/CellVisibility.cs
+++ b/src/AcDream.App/Rendering/CellVisibility.cs
@@ -176,18 +176,6 @@ public sealed class CellVisibility
     /// <summary>Full-ID lookup for O(1) neighbour resolution during BFS.</summary>
     private readonly Dictionary<uint, LoadedCell> _cellLookup = new();
 
-    /// <summary>
-    /// Phase A8 RR7.1 (2026-05-27): read-only view of every loaded cell, keyed
-    /// by full 32-bit cell id. Used by <see cref="Wb.BuildingLoader"/> at
-    /// landblock-info-arrival time so its BFS can reach cells that streamed
-    /// in on earlier frames (not just the per-frame drain). Without this view
-    /// the registry's <c>EnvCellIds</c> set was systematically short, leaving
-    /// <see cref="LoadedCell.BuildingId"/> unset on the cells the camera
-    /// actually enters — which silently routed indoor frames through the
-    /// outdoor branch.
-    /// </summary>
-    public IReadOnlyDictionary<uint, LoadedCell> AllLoadedCells => _cellLookup;
-
     /// <summary>The cell the camera was in during the last <see cref="ComputeVisibility"/> call.</summary>
     private LoadedCell? _lastCameraCell;
 
diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index 6c26170..d6ecebb 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -5696,21 +5696,12 @@ public sealed class GameWindow : IDisposable
         _terrain.AddLandblockWithMesh(lb.LandblockId, meshData, origin);
 
         // Step 4: drain pending LoadedCells from the worker thread.
-        // Phase A8 RR7.1 (2026-05-27): also late-stamp BuildingId on each
-        // arriving cell if the landblock's BuildingRegistry already exists
-        // (cells loaded after the registry-build pass at line ~5876). Cells
-        // arriving BEFORE the registry are stamped by BuildingLoader.Build
-        // itself via the AllLoadedCells dict.
+        // Also collect into a local dict for the BuildingLoader stamping pass below.
+        var drainedCells = new System.Collections.Generic.Dictionary<uint, LoadedCell>();
         while (_pendingCells.TryTake(out var cell))
         {
             _cellVisibility.AddCell(cell);
-            uint cellLbId = cell.CellId & 0xFFFF0000u;
-            if (_buildingRegistries.TryGetValue(cellLbId, out var existingReg))
-            {
-                var bs = existingReg.GetBuildingsContainingCell(cell.CellId);
-                if (bs.Count > 0)
-                    cell.BuildingId = bs[0].BuildingId;
-            }
+            drainedCells[cell.CellId] = cell;
         }
 
         // Compute the per-landblock AABB for frustum culling. XY from the
@@ -5872,20 +5863,18 @@ public sealed class GameWindow : IDisposable
             _physicsEngine.AddLandblock(lb.LandblockId, terrainSurface, cellSurfaces,
                 portalPlanes, origin.X, origin.Y);
 
-            // Phase A8 (2026-05-26, fixed 2026-05-27 RR7.1): build per-landblock
-            // BuildingRegistry from LandBlockInfo.Buildings, stamping
-            // LoadedCell.BuildingId for each cell in a building's cell set.
-            // Uses _cellVisibility.AllLoadedCells (every cell loaded so far,
-            // not just the per-frame drain) so the BFS can reach cells that
-            // streamed in on earlier frames. Cells arriving AFTER this build
-            // pass get stamped at drain time (see _pendingCells loop above).
-            // Cells without a building stay at BuildingId == null (outdoor
-            // surface cells; dungeon cells not in LandBlockInfo.Buildings).
+            // Phase A8 (2026-05-26): build per-landblock BuildingRegistry from
+            // LandBlockInfo.Buildings, stamping LoadedCell.BuildingId for each cell
+            // in a building's cell set. Uses the already-drained drainedCells dict
+            // (LoadedCells registered this frame) so stamping and registry build
+            // happen in the same render-thread pass — no extra dat reads required.
+            // Cells without a building stay at BuildingId == null (outdoor surface
+            // cells; dungeon cells not enumerated in LandBlockInfo.Buildings).
             if (lbInfo is not null)
             {
                 _buildingRegistries[lb.LandblockId] =
                     AcDream.App.Rendering.Wb.BuildingLoader.Build(
-                        lbInfo, lb.LandblockId, _cellVisibility.AllLoadedCells);
+                        lbInfo, lb.LandblockId, drainedCells);
             }
         }