gewarren · Jul 7, 2026 · Jul 7, 2026 · Jul 7, 2026 · Jul 7, 2026 · Jul 7, 2026
@@ -3,8 +3,6 @@ description: This template is for .NET product team members to report breaking c
 title: "[Breaking change]: "
 labels:
   - breaking-change
-  - Pri1
-  - doc-idea
 assignees:
  - gewarren
 body:

@@ -39,8 +39,15 @@ See [Breaking changes in ASP.NET Core 11](/aspnet/core/breaking-changes/11/overv
 
 | Title                                                          | Type of change    |
 |----------------------------------------------------------------|-------------------|
+| [API obsoletions](cryptography/11/obsolete-apis.md)            | Source incompatible |
 | [DSA removed from macOS](cryptography/11/dsa-removed-macos.md) | Behavioral change |
 
+## Deployment
+
+| Title | Type of change    |
+|-------|-------------------|
+| [configProperties in .runtimeconfig.dev.json override .runtimeconfig.json](deployment/11/runtimeconfigdev-configproperties-precedence.md) | Behavioral change |
+
 <!--
 ## Entity Framework Core
 

@@ -2,11 +2,12 @@
 title: "Breaking change: .NET 11 obsoletions with custom IDs"
 titleSuffix: ""
 description: Learn about the APIs that have been marked as obsolete in .NET 11 with a custom diagnostic ID.
-ms.date: 04/03/2026
+ms.date: 07/06/2026
+ai-usage: ai-assisted
 ---
 # API obsoletions with non-default diagnostic IDs (.NET 11)
 
-Some APIs have been marked as obsolete, starting in .NET 11.
+Some APIs are marked as obsolete, starting in .NET 11.
 
 This breaking change is specific to APIs that have been marked as obsolete *with a custom diagnostic ID*. Suppressing the default obsoletion diagnostic ID, which is [CS0618](../../../../csharp/language-reference/compiler-messages/cs0618.md) for the C# compiler, does not suppress the warnings that the compiler generates when these APIs are used.
 
@@ -43,6 +44,7 @@ These obsoletions can affect [source compatibility](../../categories.md#source-c
 
 ## See also
 
+- [Cryptography obsoletions (.NET 11)](../../cryptography/11/obsolete-apis.md)
 - [API obsoletions with non-default diagnostic IDs (.NET 10)](../10.0/obsolete-apis.md)
 - [API obsoletions with non-default diagnostic IDs (.NET 9)](../9.0/obsolete-apis-with-custom-diagnostics.md)
 - [API obsoletions with non-default diagnostic IDs (.NET 8)](../8.0/obsolete-apis-with-custom-diagnostics.md)

@@ -0,0 +1,49 @@
+---
+title: "Breaking change: .NET 11 obsoletions in cryptography"
+titleSuffix: ""
+description: Learn about the cryptography APIs that have been marked as obsolete in .NET 11.
+ms.date: 07/06/2026
+ai-usage: ai-assisted
+---
+# Cryptography obsoletions (.NET 11)
+
+Some cryptography APIs are marked as obsolete, starting in .NET 11.
+
+For obsoletions in other core .NET library areas, see [API obsoletions with non-default diagnostic IDs (.NET 11)](../../core-libraries/11/obsolete-apis.md).
+
+## Previous behavior
+
+Previously, you could use these APIs without any compile-time warnings about obsoletion.
+
+## New behavior
+
+In .NET 11 and later versions, using these APIs produces a compile-time diagnostic.
+
+The following table lists the custom diagnostic IDs and their corresponding warning messages.
+
+| Diagnostic ID | Description | Severity |
+|---------------|-------------|----------|
+| [SYSLIB0065](../../../../fundamentals/syslib-diagnostics/syslib0065.md) | The `set` accessor of <xref:System.Security.Cryptography.AsnEncodedData.RawData?displayProperty=nameWithType> is obsolete. Use the constructor of the appropriate type to decode data, or use <xref:System.Security.Cryptography.AsnEncodedData.CopyFrom(System.Security.Cryptography.AsnEncodedData)?displayProperty=nameWithType> for mutable scenarios. | Warning |
+
+## Version introduced
+
+.NET 11 Preview 6
+
+## Type of breaking change
+
+These obsoletions can affect [source compatibility](../../categories.md#source-compatibility).
+
+## Recommended action
+
+If you must keep use the obsolete APIs, suppress the warning by using the custom diagnostic ID.
+
+## Affected APIs
+
+### SYSLIB0065
+
+- `set` accessor of <xref:System.Security.Cryptography.AsnEncodedData.RawData?displayProperty=fullName>
+
+## See also
+
+- [SYSLIB0065: AsnEncodedData.RawData setter is obsolete](../../../../fundamentals/syslib-diagnostics/syslib0065.md)
+- [API obsoletions with non-default diagnostic IDs (.NET 11)](../../core-libraries/11/obsolete-apis.md)
@@ -0,0 +1,74 @@
+---
+title: "Breaking change: configProperties in .runtimeconfig.dev.json override .runtimeconfig.json"
+description: "Learn about the breaking change in .NET 11 where configProperties in .runtimeconfig.dev.json override matching configProperties in .runtimeconfig.json."
+ms.date: 07/05/2026
+ai-usage: ai-assisted
+---
+
+# configProperties in .runtimeconfig.dev.json override .runtimeconfig.json
+
+If an app defines the same runtime `configProperties` key in both `.runtimeconfig.json` and `.runtimeconfig.dev.json`, the `.runtimeconfig.dev.json` value takes precedence.
+
+## Version introduced
+
+.NET 11 Preview 6
+
+## Previous behavior
+
+Previously, `.runtimeconfig.json` took precedence over `.runtimeconfig.dev.json` for duplicate `configProperties` keys.
+
+For example:
+
+```json
+// app.runtimeconfig.json
+{
+  "runtimeOptions": {
+    "configProperties": {
+      "System.GC.Concurrent": true
+    }
+  }
+}
+```
+
+```json
+// app.runtimeconfig.dev.json
+{
+  "runtimeOptions": {
+    "configProperties": {
+      "System.GC.Concurrent": false
+    }
+  }
+}
+```
+
+With this configuration, the runtime used `System.GC.Concurrent: true`.
+
+## New behavior
+
+To support development-time overrides in .NET 11, `.runtimeconfig.dev.json` takes precedence over `.runtimeconfig.json` for duplicate `configProperties` keys.
+
+Using the same example, the runtime now uses `System.GC.Concurrent: false`.
+
+## Type of breaking change
+
+This change is a [behavioral change](../../categories.md#behavioral-change).
+
+## Reason for change
+
+This change enables developers to override production settings during development without modifying production configuration files.
+
+For more information, see [dotnet/runtime#126606](https://github.com/dotnet/runtime/issues/126606).
+
+## Recommended action
+
+For predictable production behavior, only place development-time overrides in `.runtimeconfig.dev.json`.
+
+To prevent a development-time override, remove the duplicate key from `.runtimeconfig.dev.json`.
+
+## Affected APIs
+
+None.
+
+## See also
+
+- [.NET runtime configuration settings](../../../runtime-config/index.md)
@@ -36,8 +36,14 @@ items:
                 href: core-libraries/11/ziparchive-createasync-eager-load.md
           - name: Cryptography
             items:
+              - name: API obsoletions
+                href: cryptography/11/obsolete-apis.md
               - name: DSA removed from macOS
                 href: cryptography/11/dsa-removed-macos.md
+          - name: Deployment
+            items:
+              - name: configProperties in .runtimeconfig.dev.json override .runtimeconfig.json
+                href: deployment/11/runtimeconfigdev-configproperties-precedence.md
           - name: Extensions
             items:
               - name: IHost.RunAsync and IHost.StopAsync throw when a BackgroundService fails

@@ -39,6 +39,10 @@ Specify runtime configuration options in the **configProperties** section of the
 }
 ```
 
+Starting in .NET 11, to support development-time overrides, the value in *[appname].runtimeconfig.dev.json* takes precedence when you define the same key in `configProperties` in both *[appname].runtimeconfig.dev.json* and *[appname].runtimeconfig.json*.
+
+For more information, see [configProperties in .runtimeconfig.dev.json override .runtimeconfig.json](../compatibility/deployment/11/runtimeconfigdev-configproperties-precedence.md).
+
 ### Example [appname].runtimeconfig.json file
 
 If you're placing the options in the *output* JSON file, nest them under the `runtimeOptions` property.

@@ -67,9 +67,11 @@ private static void ShowIndentation()
 
         // First content line begins at column 0 of the value:
         Console.WriteLine(xml);
-        // <order id="42">
-        //     <item>book</item>
-        // </order>
+        /* Output:
+           <order id="42">
+               <item>book</item>
+           </order>
+         */
         // </Indentation>
     }
 

@@ -87,7 +87,9 @@ The following table lists the `SYSLIB0XXX` obsoletions in .NET 5+.
 | [SYSLIB0060](syslib0060.md) | Warning | Constructors on <xref:System.Security.Cryptography.Rfc2898DeriveBytes?displayProperty=nameWithType> are obsolete. Use <xref:System.Security.Cryptography.Rfc2898DeriveBytes.Pbkdf2*?displayProperty=nameWithType> instead. |
 | [SYSLIB0061](syslib0061.md) | Warning | The `Queryable` <xref:System.Linq.Queryable.MaxBy``2(System.Linq.IQueryable{``0},System.Linq.Expressions.Expression{System.Func{``0,``1}},System.Collections.Generic.IComparer{``0})?displayProperty=nameWithType> and <xref:System.Linq.Queryable.MinBy``2(System.Linq.IQueryable{``0},System.Linq.Expressions.Expression{System.Func{``0,``1}},System.Collections.Generic.IComparer{``0})?displayProperty=nameWithType> taking an `IComparer<TSource>` are obsolete. Use the new ones that take an `IComparer<TKey>`. |
 | [SYSLIB0062](syslib0062.md) | Warning | <xref:System.Xml.Xsl.XsltSettings.EnableScript?displayProperty=nameWithType> is obsolete. |
+| [SYSLIB0063](syslib0063.md) | Warning | The <xref:System.IO.Pipes.NamedPipeClientStream> constructor that has an `isConnected` parameter is obsolete because the argument has no effect. Use the constructor that accepts `direction`, `isAsync`, and `safePipeHandle`. |
 | [SYSLIB0064](syslib0064.md) | Warning | <xref:System.Security.Cryptography.RSACryptoServiceProvider.Encrypt(System.Byte[],System.Boolean)?displayProperty=nameWithType> and <xref:System.Security.Cryptography.RSACryptoServiceProvider.Decrypt(System.Byte[],System.Boolean)?displayProperty=nameWithType> are obsolete. Use the overloads that accept an <xref:System.Security.Cryptography.RSAEncryptionPadding> instead. |
+| [SYSLIB0065](syslib0065.md) | Warning | The `set` accessor of <xref:System.Security.Cryptography.AsnEncodedData.RawData?displayProperty=nameWithType> is obsolete. Use the constructor of the appropriate type to decode data, or use <xref:System.Security.Cryptography.AsnEncodedData.CopyFrom(System.Security.Cryptography.AsnEncodedData)?displayProperty=nameWithType> for mutable scenarios. |
 
 ## EXTOBS obsoletions
 

@@ -160,13 +160,13 @@ The following table provides an index to the `SYSLIB1XXX` diagnostics in .NET 6
 | [SYSLIB1220][1220] | JsonSourceGenerator encountered a [JsonConverterAttribute] with an invalid type argument. |
 | [SYSLIB1221][1221] | JsonSourceGenerator does not support this C# language version. |
 | [SYSLIB1222][1222] | Constructor annotated with JsonConstructorAttribute is inaccessible. |
-| [SYSLIB1223][1223] | Constructor annotated with JsonConstructorAttribute is inaccessible. |
+| [SYSLIB1223][1223] | Attributes deriving from JsonConverterAttribute are not supported by the source generator. |
 | [SYSLIB1224][1224] | Types annotated with JsonSerializableAttribute must be classes deriving from JsonSerializerContext. |
-| [SYSLIB1225][1225] | (Reserved for System.Text.Json.SourceGeneration.) |
-| [SYSLIB1226][1226] | (Reserved for System.Text.Json.SourceGeneration.) |
-| [SYSLIB1227][1227] | (Reserved for System.Text.Json.SourceGeneration.) |
-| [SYSLIB1228][1228] | (Reserved for System.Text.Json.SourceGeneration.) |
-| [SYSLIB1229][1229] | (Reserved for System.Text.Json.SourceGeneration.) |
+| [SYSLIB1225][1225] | Type includes a ref-like property, a field, or a constructor parameter. |
+| [SYSLIB1226][1226] | `JsonIgnoreCondition.Always` is not valid on type-level `JsonIgnoreAttribute` annotations. |
+| [SYSLIB1227][1227] | Union case types cannot be unambiguously classified by JSON value type. |
+| [SYSLIB1228][1228] | Union type shape is not a valid C# union. |
+| [SYSLIB1229][1229] | Open generic derived type could not be resolved for the polymorphic base type. |
 | [SYSLIB1230][1230] | Deriving from a `GeneratedComInterface`-attributed interface defined in another assembly is not supported. |
 
 <!-- Include adds ## Suppress warnings (H2 heading) -->

@@ -0,0 +1,50 @@
+---
+title: SYSLIB0063 warning - NamedPipeClientStream constructor with isConnected is obsolete
+description: Learn about the obsoletion of the NamedPipeClientStream constructor that includes an isConnected argument. Use of this constructor generates compile-time warning SYSLIB0063.
+ms.date: 07/06/2026
+ai-usage: ai-assisted
+f1_keywords:
+  - SYSLIB0063
+---
+
+# SYSLIB0063: NamedPipeClientStream constructor with isConnected is obsolete
+
+Starting in .NET 11, the <xref:System.IO.Pipes.NamedPipeClientStream.%23ctor(System.IO.Pipes.PipeDirection,System.Boolean,System.Boolean,Microsoft.Win32.SafeHandles.SafePipeHandle)?displayProperty=nameWithType> constructor is obsolete. Calling this constructor in code generates warning `SYSLIB0063` at compile time.
+
+## Reason for obsoletion
+
+The `isConnected` argument on this constructor has no effect. To avoid confusion, use the constructor that omits this argument.
+
+## Workaround
+
+Use <xref:System.IO.Pipes.NamedPipeClientStream.%23ctor(System.IO.Pipes.PipeDirection,System.Boolean,Microsoft.Win32.SafeHandles.SafePipeHandle)?displayProperty=nameWithType> instead.
+
+## Suppress a warning
+
+If you must use the obsolete API, you can suppress the warning in code or in your project file.
+
+To suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the warning.
+
+```csharp
+// Disable the warning.
+#pragma warning disable SYSLIB0063
+
+// Code that uses obsolete API.
+// ...
+
+// Re-enable the warning.
+#pragma warning restore SYSLIB0063
+```
+
+To suppress all the `SYSLIB0063` warnings in your project, add a `<NoWarn>` property to your project file.
+
+```xml
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+   ...
+   <NoWarn>$(NoWarn);SYSLIB0063</NoWarn>
+  </PropertyGroup>
+</Project>
+```
+
+For more information, see [Suppress warnings](obsoletions-overview.md#suppress-warnings).
@@ -0,0 +1,73 @@
+---
+title: SYSLIB0065 warning - AsnEncodedData.RawData setter is obsolete
+description: Learn about the obsoletion of the AsnEncodedData.RawData property setter. Use of this setter generates compile-time warning SYSLIB0065.
+ms.date: 07/05/2026
+ai-usage: ai-assisted
+f1_keywords:
+  - SYSLIB0065
+---
+
+# SYSLIB0065: AsnEncodedData.RawData setter is obsolete
+
+Starting in .NET 11, the `set` accessor of <xref:System.Security.Cryptography.AsnEncodedData.RawData?displayProperty=nameWithType> is obsolete. Setting this property in code generates warning `SYSLIB0065` at compile time.
+
+## Reason for obsoletion
+
+<xref:System.Security.Cryptography.AsnEncodedData> represents an ASN.1-encoded object. Many types derive from it, such as <xref:System.Security.Cryptography.X509Certificates.X509BasicConstraintsExtension>, and cache their decoded representation so that property access doesn't repeatedly decode the ASN.1.
+
+Because `RawData` is not `virtual`, setting it on a derived instance causes a discrepancy between the cached decoded state and the new raw data. The derived type can't detect that the raw data changed, so it continues to return stale decoded values. For example:
+
+```csharp
+X509BasicConstraintsExtension extension = new(
+    certificateAuthority: true,
+    hasPathLengthConstraint: true,
+    pathLengthConstraint: 3,
+    critical: true);
+
+X509BasicConstraintsExtension decoded = new();
+decoded.RawData = extension.RawData;
+Console.WriteLine(decoded.CertificateAuthority);      // Unexpectedly prints False
+Console.WriteLine(decoded.HasPathLengthConstraint);   // Unexpectedly prints False
+Console.WriteLine(decoded.PathLengthConstraint);      // Unexpectedly prints 0
+```
+
+## Workaround
+
+To maintain coherency between the decoded state and the underlying data, use the constructor of the appropriate type to decode data. Treat instances as read-only—construct a new instance instead of reusing an existing one.
+
+```csharp
+// Instead of setting RawData, use the constructor.
+X509BasicConstraintsExtension decoded = new(extension, extension.Critical);
+```
+
+If you need mutable behavior, use <xref:System.Security.Cryptography.AsnEncodedData.CopyFrom(System.Security.Cryptography.AsnEncodedData)?displayProperty=nameWithType>. The `CopyFrom` method is `virtual`, so derived types can invalidate their decoded state when the raw data changes.
+
+## Suppress a warning
+
+If you must use the obsolete setter, you can suppress the warning in code or in your project file.
+
+To suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the warning.
+
+```csharp
+// Disable the warning.
+#pragma warning disable SYSLIB0065
+
+// Code that uses obsolete API.
+// ...
+
+// Re-enable the warning.
+#pragma warning restore SYSLIB0065
+```
+
+To suppress all `SYSLIB0065` warnings in your project, add a `<NoWarn>` property to your project file.
+
+```xml
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+   ...
+   <NoWarn>$(NoWarn);SYSLIB0065</NoWarn>
+  </PropertyGroup>
+</Project>
+```
+
+For more information, see [Suppress warnings](obsoletions-overview.md#suppress-warnings).
@@ -25,8 +25,8 @@ The following table shows the diagnostic IDs for System.Text.Json source-generat
 |  `SYSLIB1222` | Constructor annotated with `JsonConstructorAttribute` is inaccessible. |
 |  `SYSLIB1223` | Attributes deriving from `JsonConverterAttribute` are not supported by the source generator. |
 |  `SYSLIB1224` | Types annotated with `JsonSerializableAttribute` must be classes deriving from `JsonSerializerContext`. |
-|  `SYSLIB1225` | Type includes `ref` like property, field, or constructor parameter. |
-|  `SYSLIB1226` | Reserved for System.Text.Json.SourceGeneration. |
-|  `SYSLIB1227` | Reserved for System.Text.Json.SourceGeneration. |
-|  `SYSLIB1228` | Reserved for System.Text.Json.SourceGeneration. |
-|  `SYSLIB1229` | Reserved for System.Text.Json.SourceGeneration. |
+|  `SYSLIB1225` | Type includes a ref-like property, a field, or a constructor parameter. |
+|  `SYSLIB1226` | `JsonIgnoreCondition.Always` is not valid on type-level `JsonIgnoreAttribute` annotations. |
+|  `SYSLIB1227` | Union case types cannot be unambiguously classified by JSON value type. |
+|  `SYSLIB1228` | Union type shape is not a valid C# union. |
+|  `SYSLIB1229` | Open generic derived type could not be resolved for the polymorphic base type. |
@@ -4091,8 +4091,12 @@ items:
             href: ../../fundamentals/syslib-diagnostics/syslib0061.md
           - name: SYSLIB0062
             href: ../../fundamentals/syslib-diagnostics/syslib0062.md
+          - name: SYSLIB0063
+            href: ../../fundamentals/syslib-diagnostics/syslib0063.md
           - name: SYSLIB0064
             href: ../../fundamentals/syslib-diagnostics/syslib0064.md
+          - name: SYSLIB0065
+            href: ../../fundamentals/syslib-diagnostics/syslib0065.md
       - name: Experimental features
         items:
           - name: Overview