WN: 10 Prev 7: Microsoft.OpenAPI breaking change (#35942)

* WN: 10 Prev 7: Microsoft.OpenAPI breaking change

Author: wadepickett

aspnetcore/release-notes/aspnetcore-10.0.md

@@ -4,7 +4,7 @@ author: wadepickett
 description: Learn about the new features in ASP.NET Core in .NET 10.
 ms.author: wpickett
 ms.custom: mvc
-ms.date: 8/11/2025
+ms.date: 08/13/2025
 uid: aspnetcore-10
 ---
 # What's new in ASP.NET Core in .NET 10

aspnetcore/release-notes/aspnetcore-10/includes/OpenApiNetUpdatePrev.md

@@ -1,4 +1,12 @@
 ### Upgrade Microsoft.OpenApi to 2.0.0
 
-The [`Microsoft.OpenApi`](https://www.nuget.org/packages/Microsoft.OpenApi/) library used for OpenAPI document generation in ASP.NET Core has been upgraded to version 2.0.0 (GA).  
-With this update to the GA version, no further breaking changes are expected in OpenAPI document generation.
+The [`Microsoft.OpenApi`](https://www.nuget.org/packages/Microsoft.OpenApi/) library used for OpenAPI document generation in ASP.NET Core has been upgraded to version 2.0.0 (GA).
+
+#### Breaking changes in 2.0.0
+
+The following breaking changes were introduced in the preview releases and remain in the GA version. These primarily affect users who implement document, operation, or schema transformers:
+
+* [Ephemeral object properties are now in Metadata](https://github.com/microsoft/OpenAPI.NET/blob/main/docs/upgrade-guide-2.md#ephemeral-object-properties-are-now-in-metadata)
+* [Use HTTP Method Object Instead of Enum](https://github.com/microsoft/OpenAPI.NET/blob/main/docs/upgrade-guide-2.md#use-http-method-object-instead-of-enum)
+
+With the update to the GA version, no further breaking changes are expected in OpenAPI document generation.