diff --git a/Assets/Scripts/Components/MeshPainter/MeshPainter.Backend.cs b/Assets/Scripts/Components/MeshPainter/MeshPainter.Backend.cs
index 4de395b..74db91d 100644
--- a/Assets/Scripts/Components/MeshPainter/MeshPainter.Backend.cs
+++ b/Assets/Scripts/Components/MeshPainter/MeshPainter.Backend.cs
@@ -93,7 +93,12 @@ public partial class MeshPainter
     // Material slots per map, as pre-hashed IDs (this runs per stroke end - no per-call allocations).
     // MSO: one mask map drives three URP slots: _MetallicGlossMap (R/A) + _OcclusionMap (G) +
     // _ParallaxMap (G = occlusion reused as a 0.5-centred height for parallax/relief).
-    private static readonly int[][] MapPropIds =
+    // Built lazily on first use (runtime): the *Id fields live in the MeshPainter.cs partial and the
+    // static field-initializer order ACROSS partial files is unspecified - a plain field initializer
+    // here can run first and capture 0 for every id, so HasProperty(0) fails and no map ever binds
+    // (white defaults -> full-glossy + emissive). Deferring to first access sidesteps that ordering.
+    private static int[][] _mapPropIds;
+    private static int[][] MapPropIds => _mapPropIds ??= new[]
     {
         new[] { BaseMapId, MainTexId },                              // MAP_ALBEDO
         new[] { MetallicGlossMapId, OcclusionMapId, ParallaxMapId }, // MAP_MSO