diff --git a/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs b/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
index b934ade..10a14f4 100644
--- a/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
+++ b/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
@@ -1089,6 +1089,41 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
         }
     }
 
+    /// <summary>
+    /// Phase A8 RR5 (2026-05-26): per-building draw overload. Walks only
+    /// entities whose ParentCellId is in <paramref name="cellIds"/>, plus
+    /// outdoor-style entities matching the EntitySet partition. Used by
+    /// the indoor render branch to scope rendering to the camera-buildings'
+    /// cells.
+    ///
+    /// <para>Mirrors the existing visibleCellIds-based Draw but with an
+    /// explicit cell list (not the BFS-derived visibility set). The semantic
+    /// difference is at the caller: cellIds = the camera-buildings' EnvCellIds,
+    /// not the portal BFS result. The dispatcher's internal logic is identical
+    /// — it filters indoor entities by membership in the provided set.</para>
+    /// </summary>
+    public void Draw(
+        ICamera camera,
+        IEnumerable<(uint LandblockId, Vector3 AabbMin, Vector3 AabbMax,
+                     IReadOnlyList<WorldEntity> Entities,
+                     IReadOnlyDictionary<uint, WorldEntity>? AnimatedById)> landblockEntries,
+        IReadOnlyCollection<uint> cellIds,
+        FrustumPlanes? frustum = null,
+        uint? neverCullLandblockId = null,
+        HashSet<uint>? animatedEntityIds = null,
+        EntitySet set = EntitySet.All)
+    {
+        // Adapt IReadOnlyCollection<uint> → HashSet<uint> for the existing path.
+        // If the caller already passed a HashSet, avoid re-wrapping.
+        HashSet<uint> cellIdSet = cellIds is HashSet<uint> hs ? hs : new HashSet<uint>(cellIds);
+        Draw(camera, landblockEntries,
+             frustum: frustum,
+             neverCullLandblockId: neverCullLandblockId,
+             visibleCellIds: cellIdSet,
+             animatedEntityIds: animatedEntityIds,
+             set: set);
+    }
+
     private static IndirectGroupInput ToInput(InstanceGroup g) => new(
         IndexCount:    g.IndexCount,
         FirstIndex:    g.FirstIndex,
@@ -1400,6 +1435,34 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
         return output;
     }
 
+    /// <summary>
+    /// Phase A8 RR5 (2026-05-26): pure-data walk for the explicit cellIds
+    /// overload. Used by RR7's IndoorPass to render only the camera-buildings'
+    /// cells (instead of the visibility-derived set).
+    ///
+    /// <para>Indoor entities (ParentCellId set) gated by membership in
+    /// <paramref name="cellIds"/>. Building shells (IsBuildingShell) pass
+    /// unconditionally when <paramref name="set"/> == IndoorPass. Outdoor
+    /// scenery is excluded by the EntitySet partition (no cell-list gate
+    /// needed — EntityMatchesSet handles it).</para>
+    /// </summary>
+    public static List<uint> WalkEntitiesForTestByCellIds(
+        IEnumerable<AcDream.Core.World.WorldEntity> entities,
+        IReadOnlyCollection<uint> cellIds,
+        EntitySet set)
+    {
+        var result = new List<uint>();
+        foreach (var entity in entities)
+        {
+            if (!EntityMatchesSet(entity, set)) continue;
+            if (entity.MeshRefs.Count == 0) continue;
+            if (entity.ParentCellId.HasValue && !cellIds.Contains(entity.ParentCellId.Value))
+                continue;
+            result.Add(entity.Id);
+        }
+        return result;
+    }
+
     public void Dispose()
     {
         if (_disposed) return;
diff --git a/tests/AcDream.Core.Tests/Rendering/Wb/WbDrawDispatcherCellIdsOverloadTests.cs b/tests/AcDream.Core.Tests/Rendering/Wb/WbDrawDispatcherCellIdsOverloadTests.cs
new file mode 100644
index 0000000..5b52f57
--- /dev/null
+++ b/tests/AcDream.Core.Tests/Rendering/Wb/WbDrawDispatcherCellIdsOverloadTests.cs
@@ -0,0 +1,90 @@
+// Phase A8 RR5 — verify WbDrawDispatcher.WalkEntitiesForTestByCellIds,
+// the pure-data companion to the new Draw(cellIds:) production overload.
+//
+// Semantics: indoor entities (ParentCellId.HasValue) are gated by explicit
+// membership in cellIds. Building shells (IsBuildingShell) always pass.
+// Outdoor scenery (no ParentCellId, not a shell) is excluded by EntitySet.IndoorPass.
+
+using System.Collections.Generic;
+using System.Numerics;
+using AcDream.App.Rendering.Wb;
+using AcDream.Core.World;
+using Xunit;
+
+namespace AcDream.Core.Tests.Rendering.Wb;
+
+public class WbDrawDispatcherCellIdsOverloadTests
+{
+    private static WorldEntity CellEnt(uint id, uint cellId) => new()
+    {
+        Id = id,
+        SourceGfxObjOrSetupId = 0x01000001u,
+        ParentCellId = cellId,
+        MeshRefs = new List<MeshRef> { new(0x01000001u, Matrix4x4.Identity) },
+        Position = Vector3.Zero,
+        Rotation = Quaternion.Identity,
+    };
+
+    private static WorldEntity OutdoorScenery(uint id) => new()
+    {
+        Id = id,
+        SourceGfxObjOrSetupId = 0x01000001u,
+        ParentCellId = null,
+        IsBuildingShell = false,
+        MeshRefs = new List<MeshRef> { new(0x01000001u, Matrix4x4.Identity) },
+        Position = Vector3.Zero,
+        Rotation = Quaternion.Identity,
+    };
+
+    private static WorldEntity BuildingShell(uint id) => new()
+    {
+        Id = id,
+        SourceGfxObjOrSetupId = 0x02000001u,
+        ParentCellId = null,
+        IsBuildingShell = true,
+        MeshRefs = new List<MeshRef> { new(0x01000001u, Matrix4x4.Identity) },
+        Position = Vector3.Zero,
+        Rotation = Quaternion.Identity,
+    };
+
+    [Fact]
+    public void WalkEntitiesByCellIds_IncludesOnlyEntitiesInListedCells()
+    {
+        var entities = new List<WorldEntity>
+        {
+            CellEnt(0x40000001u, 0xA9B40150u),  // in listed cells
+            CellEnt(0x40000002u, 0xA9B40151u),  // in listed cells
+            CellEnt(0x40000003u, 0xA9B40999u),  // OUT — not in list
+            BuildingShell(0xC0000001u),          // always included (IsBuildingShell)
+            OutdoorScenery(0xC0000002u),         // OUT — not a shell, not in cell list
+        };
+        var cellIds = new HashSet<uint> { 0xA9B40150u, 0xA9B40151u };
+
+        var result = WbDrawDispatcher.WalkEntitiesForTestByCellIds(
+            entities, cellIds, set: WbDrawDispatcher.EntitySet.IndoorPass);
+
+        Assert.Equal(3, result.Count);
+        Assert.Contains(0x40000001u, result);
+        Assert.Contains(0x40000002u, result);
+        Assert.Contains(0xC0000001u, result);
+        Assert.DoesNotContain(0x40000003u, result);
+        Assert.DoesNotContain(0xC0000002u, result);
+    }
+
+    [Fact]
+    public void WalkEntitiesByCellIds_EmptyCellList_StillIncludesBuildingShells()
+    {
+        var entities = new List<WorldEntity>
+        {
+            CellEnt(0x40000001u, 0xA9B40150u),
+            BuildingShell(0xC0000001u),
+        };
+
+        var result = WbDrawDispatcher.WalkEntitiesForTestByCellIds(
+            entities, new HashSet<uint>(), set: WbDrawDispatcher.EntitySet.IndoorPass);
+
+        // Cell entity dropped (no cells in list); building shell still passes.
+        Assert.Single(result);
+        Assert.Contains(0xC0000001u, result);
+    }
+}