Add .NET 11 breaking change article: MVC compatibility options removed

aspnetcore/breaking-changes/11/mvc-compatibility-options-removed.md

@@ -0,0 +1,57 @@
+---
+title: "Breaking change: MVC compatibility options removed"
+ai-usage: ai-assisted
+description: "Learn about the breaking change in ASP.NET Core 11 where the MVC compatibility version APIs, including CompatibilityVersion and SetCompatibilityVersion, are removed."
+ms.date: 08/05/2026
+---
+# MVC compatibility options removed
+
+The MVC compatibility version APIs, such as `CompatibilityVersion` and `SetCompatibilityVersion`, are removed in ASP.NET Core 11. These APIs were no-ops since ASP.NET Core 3.0 and have been marked obsolete since ASP.NET Core 6.
+
+## Version introduced
+
+.NET 11 Preview 7
+
+## Previous behavior
+
+Previously, the compatibility version APIs existed and could be called, but they produced an obsoletion warning at build time and had no effect at runtime:
+
+```csharp
+services.AddMvc()
+    .SetCompatibilityVersion(CompatibilityVersion.Latest);
+```
+
+## New behavior
+
+Starting in ASP.NET Core 11, these APIs no longer exist. Code that calls them fails to compile, and existing binaries that reference them fail at runtime with a <xref:System.MissingMethodException> or <xref:System.TypeLoadException>.
+
+## Type of breaking change
+
+This change can affect [source compatibility](/dotnet/core/compatibility/categories#source-compatibility) and [binary compatibility](/dotnet/core/compatibility/categories#binary-compatibility).
+
+## Reason for change
+
+The APIs have been marked obsolete since ASP.NET Core 6 and did nothing since ASP.NET Core 3.0, so they served no value. For more information, see [dotnet/aspnetcore#67077](https://github.com/dotnet/aspnetcore/pull/67077).
+
+## Recommended action
+
+Remove any usages of these APIs. For example, change the following code:
+
+```csharp
+services.AddMvc()
+    .SetCompatibilityVersion(CompatibilityVersion.Latest);
+```
+
+To:
+
+```csharp
+services.AddMvc();
+```
+
+## Affected APIs
+
+- `Microsoft.Extensions.DependencyInjection.MvcCoreMvcBuilderExtensions.SetCompatibilityVersion`
+- `Microsoft.Extensions.DependencyInjection.MvcCoreMvcCoreBuilderExtensions.SetCompatibilityVersion`
+- `Microsoft.AspNetCore.Mvc.Infrastructure.ConfigureCompatibilityOptions<TOptions>`
+- `Microsoft.AspNetCore.Mvc.MvcCompatibilityOptions`
+- `Microsoft.AspNetCore.Mvc.CompatibilityVersion`

aspnetcore/breaking-changes/11/overview.md

@@ -21,6 +21,7 @@ If you're migrating an app to ASP.NET Core 11, the breaking changes listed here
 | [Hosting emits OpenTelemetry HTTP semantic-convention tags by default](http-activity-otel-semconv.md) | Behavioral change |
 | [Kestrel tightens HTTP protocol compliance](kestrel-strict-protocol-compliance.md) | Behavioral change |
 | [Microsoft.OpenApi upgraded to 3.x](microsoft-openapi-3x.md) | Source incompatible |
+| [MVC compatibility options removed](mvc-compatibility-options-removed.md) | Binary/source incompatible |
 | [Obsolete Blazor APIs removed](blazor-obsolete-apis-removed.md) | Source incompatible |
 | [OpenAPI document includes all ProducesResponseType entries per status code](openapi-multiple-produces-per-status.md) | Behavioral change |
 | [OpenAPI server URL no longer has a trailing slash when PathBase is empty](openapi-server-url-trailing-slash.md) | Behavioral change |

aspnetcore/mvc/compatibility-version.md

@@ -4,7 +4,7 @@ author: tdykstra
 description: Discover how the Startup class in ASP.NET Core configures services and the app's request pipeline.
 monikerRange: '>= aspnetcore-2.1'
 ms.author: tdykstra
-ms.date: 9/25/2019
+ms.date: 08/05/2026
 uid: mvc/compatibility-version
 ---
 # Compatibility version for ASP.NET Core MVC
@@ -17,6 +17,7 @@ The <xref:Microsoft.Extensions.DependencyInjection.MvcCoreMvcBuilderExtensions.S
 
 * The next minor version of ASP.NET Core may provide a new `CompatibilityVersion` value.
 * `CompatibilityVersion` values `Version_2_0` through `Version_2_2` are marked `[Obsolete(...)]`.
+* The compatibility version APIs are removed in ASP.NET Core 11. For more information, see [MVC compatibility options removed](/aspnet/core/breaking-changes/11/mvc-compatibility-options-removed).
 * See [Breaking API changes in Antiforgery, CORS, Diagnostics, Mvc, and Routing](https://github.com/aspnet/Announcements/issues/387). This list includes breaking changes for compatibility switches.
 
 To see how `SetCompatibilityVersion` works with ASP.NET Core 2.x apps, select the [ASP.NET Core 2.2 version of this article](?view=aspnetcore-2.2&preserve-view=true).

aspnetcore/mvc/overview.md

@@ -3,7 +3,7 @@ title: Overview of ASP.NET Core MVC
 author: ardalis
 description: Learn how ASP.NET Core MVC is a rich framework for building web apps and APIs using the Model-View-Controller design pattern.
 ms.author: tdykstra
-ms.date: 04/29/2026
+ms.date: 08/05/2026
 uid: mvc/overview
 ---
 # Overview of ASP.NET Core MVC
@@ -228,9 +228,7 @@ Tag Helpers provide an HTML-friendly development experience and a rich IntelliSe
 
 ## Compatibility version
 
-The <xref:Microsoft.Extensions.DependencyInjection.MvcCoreMvcBuilderExtensions.SetCompatibilityVersion*> method allows an app to opt-in or opt-out of potentially breaking behavior changes introduced in ASP.NET Core MVC 2.1 or later.
-
-For more information, see <xref:mvc/compatibility-version>.
+The `SetCompatibilityVersion` method allowed an app to opt in or opt out of potentially breaking behavior changes introduced in ASP.NET Core MVC 2.1 or later. The method is a no-op for ASP.NET Core 3.0 and later apps, and it's removed in ASP.NET Core 11. For more information, see <xref:mvc/compatibility-version> and [MVC compatibility options removed](/aspnet/core/breaking-changes/11/mvc-compatibility-options-removed).
 
 ## Additional resources
 

aspnetcore/toc.yml

@@ -29,6 +29,8 @@ items:
                 href: breaking-changes/11/kestrel-strict-protocol-compliance.md
               - name: Microsoft.OpenApi upgraded to 3.x
                 href: breaking-changes/11/microsoft-openapi-3x.md
+              - name: MVC compatibility options removed
+                href: breaking-changes/11/mvc-compatibility-options-removed.md
               - name: Obsolete Blazor APIs removed
                 href: breaking-changes/11/blazor-obsolete-apis-removed.md
               - name: OpenAPI document includes all ProducesResponseType entries per status code