Set the ID of the SSS material to 0 and of the standard material to 1

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/LayeredLit/LayeredLit.shader

         _HorizonFade("Horizon fade", Range(0.0, 5.0)) = 1.0
 
         // Stencil state
-        [HideInInspector] _StencilRef("_StencilRef", Int) = 2 // StencilBits.Standard
+        [HideInInspector] _StencilRef("_StencilRef", Int) = 2 // StencilBits.Standard (fixed at compile time)
 
         // Blending state
         [HideInInspector] _SurfaceType("__surfacetype", Float) = 0.0

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/LayeredLit/LayeredLitTessellation.shader

         _HorizonFade("Horizon fade", Range(0.0, 5.0)) = 1.0
 
         // Stencil state
-        [HideInInspector] _StencilRef("_StencilRef", Int) = 2 // StencilBits.Standard
+        [HideInInspector] _StencilRef("_StencilRef", Int) = 2 // StencilBits.Standard (fixed at compile time)
 
         // Blending state
         [HideInInspector] _SurfaceType("__surfacetype", Float) = 0.0

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Editor/BaseLitUI.cs

 
         // Properties
         // Material ID
-        protected MaterialProperty materialID = null;
-        protected const string kMaterialID = "_MaterialID";
+        protected MaterialProperty materialID  = null;
+        protected const string     kMaterialID = "_MaterialID";
+
+        protected const string     kStencilRef = "_StencilRef";
 
         // Wind
         protected MaterialProperty windEnable = null;
             bool depthOffsetEnable = material.GetFloat(kDepthOffsetEnable) > 0.0f;
             SetKeyword(material, "_DEPTHOFFSET_ON", depthOffsetEnable);
 
-            int stencilRef = (int)UnityEngine.Experimental.Rendering.HDPipeline.StencilBits.Standard; // See 'StencilBits'.
+            // Temp. material ID upgrade workaround: determine the material ID from the stencil reference value.
+            // Select the menu item [HDRenderPipeline -> Reset all material keywords] to proceed.
+            // Remove after upgrading all projects!
-                int materialID = (int)material.GetFloat(kMaterialID);
+                int sr = (int)material.GetFloat(kStencilRef);
+                Debug.Assert(sr > 0, "The stencil reference value must be greater than 0. This material will have an incorrect ID assigned to it.");
+
+                material.SetInt(kMaterialID, sr - 1);
+            }
-                switch (materialID)
-                {
-                    case (int)UnityEngine.Experimental.Rendering.HDPipeline.Lit.MaterialId.LitSSS:
-                        stencilRef = (int)UnityEngine.Experimental.Rendering.HDPipeline.StencilBits.SSS;
-                        break;
-                    case (int)UnityEngine.Experimental.Rendering.HDPipeline.Lit.MaterialId.LitStandard:
-                        stencilRef = (int)UnityEngine.Experimental.Rendering.HDPipeline.StencilBits.Standard;
-                        break;
-                    default:
-                        stencilRef = 1 + materialID;
-                        break;
-                }
+            // Set the reference value for the stencil test.
+            int stencilRef = (int)UnityEngine.Experimental.Rendering.HDPipeline.StencilBits.Standard;
+            if (material.HasProperty(kMaterialID))
+            {
+                stencilRef = 1 + (int)material.GetFloat(kMaterialID);
-            material.SetInt("_StencilRef", stencilRef);
+            material.SetInt(kStencilRef, stencilRef);
 
             bool enablePerPixelDisplacement = material.GetFloat(kEnablePerPixelDisplacement) > 0.0f;
             SetKeyword(material, "_PER_PIXEL_DISPLACEMENT", enablePerPixelDisplacement);

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.cs

         [GenerateHLSL(PackingRules.Exact)]
         public enum MaterialId
         {
-            LitStandard = 0,
-            LitSSS = 1,
+            LitSSS      = 0,
+            LitStandard = 1,
-            LitUnused = 3,
-            LitAniso = 4 // Should be the last as it is not setup by the users but generated based on anisotropy property
+            LitUnused   = 3,
+            LitAniso    = 4 // Should be the last as it is not setup by the users but generated based on anisotropy property
-            public static uint FEATURE_FLAG_MATERIAL_LIT_STANDARD = 1 << 12;
-            public static uint FEATURE_FLAG_MATERIAL_LIT_SSS = 1 << 13;
+            public static uint FEATURE_FLAG_MATERIAL_LIT_SSS      = 1 << 12;
+            public static uint FEATURE_FLAG_MATERIAL_LIT_STANDARD = 1 << 13;
-            public static uint FEATURE_FLAG_MATERIAL_LIT_ANISO = 1 << 15;
+            public static uint FEATURE_FLAG_MATERIAL_LIT_ANISO    = 1 << 15;
         }
 
         //-----------------------------------------------------------------------------

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.shader

         [HideInInspector] _UVMappingMask("_UVMappingMask", Color) = (1, 0, 0, 0)
         [Enum(TangentSpace, 0, ObjectSpace, 1)] _NormalMapSpace("NormalMap space", Float) = 0
 
-        [Enum(Standard, 0, Subsurface Scattering, 1, Specular Color, 2)] _MaterialID("MaterialId", Int) = 0
+        [Enum(Subsurface Scattering, 0, Standard, 1, Specular Color, 2)] _MaterialID("MaterialId", Int) = 1 // MaterialId.LitStandard
 
         [ToggleOff]  _EnablePerPixelDisplacement("Enable per pixel displacement", Float) = 0.0
         _PPDMinSamples("Min sample for POM", Range(1.0, 64.0)) = 5

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitData.hlsl

     surfaceData.tangentWS = input.worldToTangent[0].xyz;
 #endif
     // Init other parameters
-    surfaceData.materialId = 0;
+    surfaceData.materialId = 1; // MaterialId.LitStandard
     surfaceData.anisotropy = 0;
     surfaceData.specular = 0.04;
     surfaceData.subsurfaceRadius = 1.0;

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitDataInternal.hlsl

 
     // Mandatory to setup value to keep compiler quiet
 
-    // Layered shader only support materialId 0
-    surfaceData.materialId = 0;
+    // Layered shader only supports the standard material
+    surfaceData.materialId = 1; // MaterialId.LitStandard
 
     // All these parameters are ignore as they are re-setup outside of the layers function
     surfaceData.tangentWS = float3(0.0, 0.0, 0.0);

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitTessellation.shader

         [HideInInspector] _UVMappingMask("_UVMappingMask", Color) = (1, 0, 0, 0)
         [Enum(TangentSpace, 0, ObjectSpace, 1)] _NormalMapSpace("NormalMap space", Float) = 0
 
-        [Enum(Standard, 0, Subsurface Scattering, 1, Specular Color, 2)] _MaterialID("MaterialId", Int) = 0
+        [Enum(Subsurface Scattering, 0, Standard, 1, Specular Color, 2)] _MaterialID("MaterialId", Int) = 1 // MaterialId.LitStandard
 
         [ToggleOff]  _EnablePerPixelDisplacement("Enable per pixel displacement", Float) = 0.0
         _PPDMinSamples("Min sample for POM", Range(1.0, 64.0)) = 5

Assets/ScriptableRenderPipeline/HDRenderPipeline/Utilities.cs

     [Flags]
     public enum StencilBits
     {
-        None      = 0,
-        SSS       = 0 + Lit.MaterialId.LitSSS,       // 1
-        Standard  = 2 + Lit.MaterialId.LitStandard,  // 2
-        All       = 255 // 0xff
+        None      = 0,                              // 0
+        SSS       = 1 + Lit.MaterialId.LitSSS,      // 1
+        Standard  = 1 + Lit.MaterialId.LitStandard, // 2
+        All       = 255                             // 0xFF
     }
 
     public class Utilities