diff --git a/tests/AcDream.Core.Tests/Conformance/Issue113DoorVanishDiagnosticTests.cs b/tests/AcDream.Core.Tests/Conformance/Issue113DoorVanishDiagnosticTests.cs
index f698b0b0..78420fa2 100644
--- a/tests/AcDream.Core.Tests/Conformance/Issue113DoorVanishDiagnosticTests.cs
+++ b/tests/AcDream.Core.Tests/Conformance/Issue113DoorVanishDiagnosticTests.cs
@@ -181,6 +181,56 @@ public sealed class Issue113DoorVanishDiagnosticTests
         return n.LengthSquared() < 1e-10f ? Vector3.Zero : Vector3.Normalize(n);
     }
 
+    /// <summary>
+    /// Phase A confirmation: retail's building/cell mesh pass skips surface
+    /// batches whose CSurface type has neither Base1Image (0x2) nor
+    /// Base1ClipMap (0x4) — the skipNoTexture rule (D3DPolyRender inner draw
+    /// 0x0059d4a0; default skipNoTexture=1). Prediction: the hall's phantom
+    /// stair-ramp portal-fill polys {0,1} reference SOLID (untextured)
+    /// surfaces while cottage door/window fills reference TEXTURED surfaces —
+    /// which is exactly why retail shows doors but not the ramp.
+    /// </summary>
+    [Fact]
+    public void DumpPortalFillSurfaceTypes()
+    {
+        var datDir = ConformanceDats.ResolveDatDir();
+        if (datDir is null) { _out.WriteLine("dats unavailable — skipped"); return; }
+        using var dats = new DatCollection(datDir, DatAccessType.Read);
+
+        foreach (uint mid in new uint[] { 0x010014C3u, 0x01000827u, 0x0100082Eu, 0x01000C17u })
+        {
+            var gfx = dats.Get<DatReaderWriter.DBObjs.GfxObj>(mid);
+            if (gfx?.DrawingBSP?.Root is null) continue;
+
+            var walked = new HashSet<ushort>();
+            void Walk(DatReaderWriter.Types.DrawingBSPNode? n)
+            {
+                if (n is null) return;
+                if (n.Polygons is not null) foreach (var pid in n.Polygons) walked.Add((ushort)pid);
+                Walk(n.PosNode); Walk(n.NegNode);
+            }
+            Walk(gfx.DrawingBSP.Root);
+            var portalFills = gfx.Polygons.Keys.Where(k => !walked.Contains(k)).OrderBy(k => k).ToList();
+
+            _out.WriteLine($"=== model 0x{mid:X8}: {portalFills.Count} portal-fill polys; Surfaces list has {gfx.Surfaces.Count} entries ===");
+            foreach (var pid in portalFills)
+            {
+                var poly = gfx.Polygons[pid];
+                string Describe(short surfIdx)
+                {
+                    if (surfIdx < 0 || surfIdx >= gfx.Surfaces.Count) return $"idx{surfIdx}=OOB";
+                    uint sid = gfx.Surfaces[surfIdx];
+                    var surf = dats.Get<DatReaderWriter.DBObjs.Surface>(sid);
+                    if (surf is null) return $"0x{sid:X8}=MISSING";
+                    bool textured = surf.Type.HasFlag(DatReaderWriter.Enums.SurfaceType.Base1Image)
+                                 || surf.Type.HasFlag(DatReaderWriter.Enums.SurfaceType.Base1ClipMap);
+                    return $"0x{sid:X8} type={surf.Type} -> {(textured ? "TEXTURED (drawn)" : "SOLID (skipNoTexture SKIPS on building/cell pass)")}";
+                }
+                _out.WriteLine($"  poly {pid,3}: sides={poly.SidesType} stip={poly.Stippling} pos[{Describe(poly.PosSurface)}] neg[{Describe(poly.NegSurface)}]");
+            }
+        }
+    }
+
     /// <summary>
     /// Control group: the two #113 models (hall + cottage) whose orphans ARE
     /// the phantom geometry, for type-model comparison against the door.