diff --git a/src/AcDream.App/Rendering/RetailPViewRenderer.cs b/src/AcDream.App/Rendering/RetailPViewRenderer.cs
index e994a311..5bf7bd45 100644
--- a/src/AcDream.App/Rendering/RetailPViewRenderer.cs
+++ b/src/AcDream.App/Rendering/RetailPViewRenderer.cs
@@ -110,12 +110,17 @@ public sealed class RetailPViewRenderer
 
         foreach (var cell in ctx.NearbyBuildingCells!)
         {
-            if (cell.BuildingId is not uint buildingId)
-                continue; // outdoor surface cells (no building) don't flood
-            if (!_buildingGroups.TryGetValue(buildingId, out var group))
+            // R-A2 seam fix: a cell without a BuildingId (unstamped, or outdoor-adjacent with an exit
+            // portal) must STILL flood — the pre-R-A2 node flood reached it via a reverse portal, so
+            // dropping it (the original `continue`) left holes at building/terrain seams. Key it by its
+            // own CellId → a singleton per-entrance flood: a cell with an exit portal seeds from it, a
+            // cell with none contributes nothing (same as before). BuildingId/CellId key collisions are
+            // harmless — BuildFromExterior seeds each exit-portal cell in a group independently.
+            uint groupKey = cell.BuildingId ?? cell.CellId;
+            if (!_buildingGroups.TryGetValue(groupKey, out var group))
             {
                 group = new List<LoadedCell>();
-                _buildingGroups[buildingId] = group;
+                _buildingGroups[groupKey] = group;
             }
             group.Add(cell);
         }