diff --git a/tools/RainMeshProbe/Program.cs b/tools/RainMeshProbe/Program.cs
index 37475b1..1eaff70 100644
--- a/tools/RainMeshProbe/Program.cs
+++ b/tools/RainMeshProbe/Program.cs
@@ -28,8 +28,47 @@ using var dats = new DatCollection(datDir, DatAccessType.Read);
 
 uint[] gfxIds = { 0x01004C42u, 0x01004C44u };
 foreach (uint gid in gfxIds) ProbeRain(dats, gid);
+
+// Phase 7c: also dump every sky surface we know to test the LUMINOUS flag.
+// Two existing code comments contradict each other about whether Dereth's
+// dome/sun/moon meshes carry the LUMINOUS bit. Resolve empirically.
+Console.WriteLine();
+Console.WriteLine("================ Sky Surface LUMINOUS audit ================");
+uint[] skySurfaceIds = {
+    0x08000048u, 0x08000049u, 0x0800004Au, 0x0800004Bu,  // dome 0x010015EE
+    0x0800004Du,                                         // star sheet 0x010015EF
+    0x0800004Eu, 0x0800004Fu, 0x08000050u, 0x08000051u,  // dome 0x010015F0
+    0x08000053u, 0x08000054u, 0x08000055u, 0x08000056u,  // dome 0x010015F1
+    0x08000057u, 0x08000058u, 0x08000059u, 0x0800005Au,  // dome 0x010015F2
+    0x080000D1u,                                         // celestial 0x01001348
+    0x080000D2u,                                         // sun-like 0x01001F67
+    0x080000D6u, 0x080000D7u,                            // moon 0x01001F6A
+    0x080000D4u,                                         // cloud 0x01004C36/37
+    0x08000023u,                                         // cloud 0x01004C35
+    0x08000024u, 0x08000025u,                            // cloud 0x01004C39/3A
+    0x080000D5u,                                         // dome variant 0x010015B6
+    0x080000C5u,                                         // RAIN — control row, expected NO Luminous
+};
+foreach (uint sid in skySurfaceIds) ProbeSkySurface(dats, sid);
+
 return 0;
 
+static void ProbeSkySurface(DatCollection dats, uint sid)
+{
+    if (!dats.TryGet<Surface>(sid, out var s) || s is null)
+    { Console.WriteLine($"  Surface 0x{sid:X8} (NOT FOUND)"); return; }
+    uint t = (uint)s.Type;
+    bool luminous = (t & 0x40u) != 0u;
+    Console.Write($"  Surface 0x{sid:X8}  Type=0x{t:X8}  Luminous={(luminous ? "YES" : "no ")}  Lum={s.Luminosity:F4}  Trans={s.Translucency:F4}  ");
+    // Decode bits inline.
+    var bits = new (uint mask, string n)[] {
+        (0x01u,"B1Solid"),(0x02u,"B1Image"),(0x04u,"B1ClipMap"),(0x10u,"Translucent"),
+        (0x20u,"Diffuse"),(0x40u,"Luminous"),(0x100u,"Alpha"),(0x200u,"InvAlpha"),
+        (0x10000u,"Additive"),(0x20000u,"Detail"),
+    };
+    Console.WriteLine(string.Join("|", bits.Where(b => (t & b.mask) != 0).Select(b => b.n)));
+}
+
 static void ProbeRain(DatCollection dats, uint gid)
 {
     Console.WriteLine();