Move transparent depth prepass just after the sky to avoid problems with opaque classification for lighting.

com.unity.render-pipelines.high-definition/HDRP/RenderPipeline/HDRenderPipeline.cs

 
                         RenderSky(hdCamera, cmd);
 
+                        RenderTransparentDepthPrepass(m_CullResults, hdCamera, renderContext, cmd);
+
                         // Render pre refraction objects
                         RenderForward(m_CullResults, hdCamera, renderContext, cmd, ForwardPass.PreRefraction);
 
                         RenderForwardError(m_CullResults, hdCamera, renderContext, cmd);
 
                         // Fill depth buffer to reduce artifact for transparent object during postprocess
-                        RenderTransparentDepthPostpass(m_CullResults, hdCamera, renderContext, cmd, ForwardPass.Transparent);
+                        RenderTransparentDepthPostpass(m_CullResults, hdCamera, renderContext, cmd);
 
                         RenderColorPyramid(hdCamera, cmd, renderContext, false);
 
                     RenderOpaqueRenderList(cull, hdCamera, renderContext, cmd, m_DepthForwardOnlyPassNames, 0, HDRenderQueue.k_RenderQueue_AllOpaque);
                 }
             }
-
-            if (hdCamera.frameSettings.enableTransparentPrepass)
-            {
-                // Render transparent depth prepass after opaque one
-                using (new ProfilingSample(cmd, "Transparent Depth Prepass", CustomSamplerId.TransparentDepthPrepass.GetSampler()))
-                {
-                    RenderTransparentRenderList(cull, hdCamera, renderContext, cmd, m_TransparentDepthPrepassNames);
-                }
-            }
         }
 
         // RenderGBuffer do the gbuffer pass. This is solely call with deferred. If we use a depth prepass, then the depth prepass will perform the alpha testing for opaque apha tested and we don't need to do it anymore
                 {
                     drawSettings.SetShaderPassName(0, HDShaderPassNames.s_MeshDecals3RTName);
                 }
-                                               
+
                 FilterRenderersSettings filterRenderersSettings = new FilterRenderersSettings(true)
                 {
                     renderQueueRange = HDRenderQueue.k_RenderQueue_AllOpaque
             }
         }
 
-        void RenderTransparentDepthPostpass(CullResults cullResults, HDCamera hdCamera, ScriptableRenderContext renderContext, CommandBuffer cmd, ForwardPass pass)
+        void RenderTransparentDepthPrepass(CullResults cull, HDCamera hdCamera, ScriptableRenderContext renderContext, CommandBuffer cmd)
+        {
+            if (hdCamera.frameSettings.enableTransparentPrepass)
+            {
+                // Render transparent depth prepass after opaque one
+                using (new ProfilingSample(cmd, "Transparent Depth Prepass", CustomSamplerId.TransparentDepthPrepass.GetSampler()))
+                {
+                    RenderTransparentRenderList(cull, hdCamera, renderContext, cmd, m_TransparentDepthPrepassNames);
+                }
+            }
+        }
+
+        void RenderTransparentDepthPostpass(CullResults cullResults, HDCamera hdCamera, ScriptableRenderContext renderContext, CommandBuffer cmd)
         {
             if (!hdCamera.frameSettings.enableTransparentPostpass)
                 return;