diff --git a/README.md b/README.md
index 3e65b86..8e150e3 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,8 @@ Here's an example of some of the new features that **PolySharp** can enable down
 - `[OverloadResolutionPriority]` (needed for [overload resolution priority](https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-13#overload-resolution-priority))
 - `[ParamsCollection]` (needed for [params collection](https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-13#params-collections))
 - `[ConstantExpected]` (see [proposal](https://github.com/dotnet/runtime/issues/33771))
+- `[CompilerLoweringPreserve]` (see [proposal](https://github.com/dotnet/runtime/issues/103430))
+- `[ExtensionMarker]` (needed for [extensions](https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-14#extension-members))
 
 To leverage them, make sure to bump your C# language version. You can do this by setting the `<LangVersion>` MSBuild property in your project. For instance, by adding `<LangVersion>13.0</LangVersion>` (or your desired C# version) to the first `<PropertyGroup>` of your .csproj file. For more info on this, [see here](https://sergiopedri.medium.com/enabling-and-using-c-9-features-on-older-and-unsupported-runtimes-ce384d8debb), but remember that you don't need to manually copy polyfills anymore: simply adding a reference to **PolySharp** will do this for you automatically.
 
@@ -84,6 +86,7 @@ It also includes the following optional runtime-supported polyfills:
   - `[FeatureGuard]`
   - `[FeatureSwitchDefinition]`
 - `[WasmImportLinkage]` (see [here](https://github.com/dotnet/runtime/pull/93823))
+- `[UnsafeAccessorType]` (see [here](https://github.com/dotnet/runtime/issues/90081))
 
 # Options ⚙️
 
diff --git a/src/PolySharp.Package/README.md b/src/PolySharp.Package/README.md
index 0cacf88..fc41674 100644
--- a/src/PolySharp.Package/README.md
+++ b/src/PolySharp.Package/README.md
@@ -53,6 +53,8 @@ Here's an example of some of the new features that **PolySharp** can enable down
 - `[OverloadResolutionPriority]` (needed for [overload resolution priority](https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-13#overload-resolution-priority))
 - `[ParamsCollection]` (needed for [params collection](https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-13#params-collections))
 - `[ConstantExpected]` (see [proposal](https://github.com/dotnet/runtime/issues/33771))
+- `[CompilerLoweringPreserve]` (see [proposal](https://github.com/dotnet/runtime/issues/103430))
+- `[ExtensionMarker]` (needed for [extensions](https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-14#extension-members))
 
 To leverage them, make sure to bump your C# language version. You can do this by setting the `<LangVersion>` MSBuild property in your project. For instance, by adding `<LangVersion>13.0</LangVersion>` (or your desired C# version) to the first `<PropertyGroup>` of your .csproj file. For more info on this, [see here](https://sergiopedri.medium.com/enabling-and-using-c-9-features-on-older-and-unsupported-runtimes-ce384d8debb), but remember that you don't need to manually copy polyfills anymore: simply adding a reference to **PolySharp** will do this for you automatically.
 
@@ -82,6 +84,7 @@ It also includes the following optional runtime-supported polyfills:
   - `[FeatureGuard]`
   - `[FeatureSwitchDefinition]`
 - `[WasmImportLinkage]` (see [here](https://github.com/dotnet/runtime/pull/93823))
+- `[UnsafeAccessorType]` (see [here](https://github.com/dotnet/runtime/issues/90081))
 
 # Options ⚙️
 
diff --git a/src/PolySharp.SourceGenerators/EmbeddedResources/LanguageSupport/System.Runtime.CompilerServices.CompilerLoweringPreserveAttribute.cs b/src/PolySharp.SourceGenerators/EmbeddedResources/LanguageSupport/System.Runtime.CompilerServices.CompilerLoweringPreserveAttribute.cs
new file mode 100644
index 0000000..6a54468
--- /dev/null
+++ b/src/PolySharp.SourceGenerators/EmbeddedResources/LanguageSupport/System.Runtime.CompilerServices.CompilerLoweringPreserveAttribute.cs
@@ -0,0 +1,29 @@
+// <auto-generated/>
+#pragma warning disable
+#nullable enable annotations
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// When applied to an attribute class, instructs the compiler to flow applications of that attribute,
+    /// from source code down to compiler-generated symbols. This can help IL-based analysis tools.
+    /// </summary>
+    /// <remarks>
+    /// One example where this attribute applies is in C# primary constructor parameters. If an attribute
+    /// marked with <see cref="global::System.Runtime.CompilerServices.CompilerLoweringPreserveAttribute"/> gets applied to a primary constructor
+    /// parameter, the attribute will also be applied to any compiler-generated fields storing that parameter.
+    /// </remarks>
+    [global::System.AttributeUsage(global::System.AttributeTargets.Class, Inherited = false)]
+    [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    [global::Microsoft.CodeAnalysis.Embedded]
+    internal sealed class CompilerLoweringPreserveAttribute : global::System.Attribute
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="global::System.Runtime.CompilerServices.CompilerLoweringPreserveAttribute"/> class.
+        /// </summary>
+        public CompilerLoweringPreserveAttribute() { }
+    }
+}
\ No newline at end of file
diff --git a/src/PolySharp.SourceGenerators/EmbeddedResources/LanguageSupport/System.Runtime.CompilerServices.ExtensionMarkerAttribute.cs b/src/PolySharp.SourceGenerators/EmbeddedResources/LanguageSupport/System.Runtime.CompilerServices.ExtensionMarkerAttribute.cs
new file mode 100644
index 0000000..74401fd
--- /dev/null
+++ b/src/PolySharp.SourceGenerators/EmbeddedResources/LanguageSupport/System.Runtime.CompilerServices.ExtensionMarkerAttribute.cs
@@ -0,0 +1,40 @@
+// <auto-generated/>
+#pragma warning disable
+#nullable enable annotations
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// This attribute is used to mark extension members and associate them with a specific marker type (which provides detailed information about an extension block and its receiver parameter).
+    /// This attribute should not be used by developers in source code.
+    /// </summary>
+    [global::System.ComponentModel.EditorBrowsable(EditorBrowsableState.Never)]
+    [global::System.AttributeUsage(
+        global::System.AttributeTargets.Class |
+        global::System.AttributeTargets.Struct |
+        global::System.AttributeTargets.Enum |
+        global::System.AttributeTargets.Method |
+        global::System.AttributeTargets.Property |
+        global::System.AttributeTargets.Field |
+        global::System.AttributeTargets.Event |
+        global::System.AttributeTargets.Interface |
+        global::System.AttributeTargets.Delegate,
+        Inherited = false)]
+    [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    [global::Microsoft.CodeAnalysis.Embedded]
+    internal sealed class ExtensionMarkerAttribute : global::System.Attribute
+    {
+        /// <summary>Initializes a new instance of the <see cref="global::System.Runtime.CompilerServices.ExtensionMarkerAttribute"/> class.</summary>
+        /// <param name="name">The name of the marker type this extension member is associated with.</param>
+        public ExtensionMarkerAttribute(string name)
+            => Name = name;
+
+        /// <summary>The name of the marker type this extension member is associated with.</summary>
+        public string Name { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute.cs b/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute.cs
index 6930625..96385f4 100644
--- a/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute.cs
+++ b/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute.cs
@@ -134,6 +134,8 @@ public DynamicDependencyAttribute(global::System.Diagnostics.CodeAnalysis.Dynami
         /// <summary>
         /// Gets or sets the condition in which the dependency is applicable, e.g. "DEBUG".
         /// </summary>
+        [global::System.Obsolete("This property is no longer supported.")]
+        [global::System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
         public string? Condition { get; set; }
     }
 }
\ No newline at end of file
diff --git a/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute.cs b/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute.cs
index 6edb6e2..5c3905e 100644
--- a/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute.cs
+++ b/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute.cs
@@ -43,6 +43,7 @@ namespace System.Diagnostics.CodeAnalysis
     [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
     [global::Microsoft.CodeAnalysis.Embedded]
     [global::System.Diagnostics.Conditional("MULTI_TARGETING_SUPPORT_ATTRIBUTES")]
+    [global::System.Runtime.CompilerServices.CompilerLoweringPreserveAttribute]
     internal sealed class DynamicallyAccessedMembersAttribute : global::System.Attribute
     {
         /// <summary>
diff --git a/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.UnsafeAccessorTypeAttribute.cs b/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.UnsafeAccessorTypeAttribute.cs
new file mode 100644
index 0000000..ef363d2
--- /dev/null
+++ b/src/PolySharp.SourceGenerators/EmbeddedResources/RuntimeSupported/System.Diagnostics.CodeAnalysis.UnsafeAccessorTypeAttribute.cs
@@ -0,0 +1,64 @@
+// <auto-generated/>
+#pragma warning disable
+#nullable enable annotations
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Provides access to an inaccessible type.
+    /// </summary>
+    [global::System.AttributeUsage(
+        global::System.AttributeTargets.Parameter |
+        global::System.AttributeTargets.ReturnValue,
+        AllowMultiple = false,
+        Inherited = false)]
+    [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+    [global::Microsoft.CodeAnalysis.Embedded]
+    [global::System.Diagnostics.Conditional("MULTI_TARGETING_SUPPORT_ATTRIBUTES")]
+    internal sealed class UnsafeAccessorTypeAttribute : global::System.Attribute
+    {
+        /// <summary>
+        /// Instantiates an <see cref="UnsafeAccessorTypeAttribute"/> providing access to a type supplied by <paramref name="typeName"/>.
+        /// </summary>
+        /// <param name="typeName">A fully qualified or partially qualified type name.</param>
+        /// <remarks>
+        /// <paramref name="typeName"/> is expected to follow the same rules as if it were being
+        /// passed to <see name="global::System.Type.GetType(global::System.String)"/>. When unbound generics are involved they
+        /// should follow the IL syntax of referencing a type or method generic variables using
+        /// the syntax of <c>!N</c> or <c>!!N</c> respectively, where N is the zero-based index of the
+        /// generic parameters. The generic rules defined for <see cref="global::System.Diagnostics.CodeAnalysis.UnsafeAccessorAttribute"/>
+        /// apply to this attribute as well, meaning the arity and type of generic parameter must match
+        /// the target type.
+        ///
+        /// This attribute only has behavior on parameters or return values of methods marked with <see cref="global::System.Diagnostics.CodeAnalysis.UnsafeAccessorAttribute"/>.
+        ///
+        /// This attribute should only be applied to parameters or return types of methods that are
+        /// typed as follows:
+        ///
+        /// <ul>
+        ///   <li>References should be typed as <lang>object</lang>.</li>
+        ///   <li>Byref arguments should be typed with <lang>in</lang>, <lang>ref</lang>, or <lang>out</lang> to <lang>object</lang>.</li>
+        ///   <li>Unmanaged pointers should be typed as <lang>void*</lang>.</li>
+        ///   <li>Byref arguments to reference types or arrays should be typed with <lang>in</lang>, <lang>ref</lang>, or <lang>out</lang> to <lang>object</lang>.</li>
+        ///   <li>Byref arguments to unmanaged pointer types should be typed with <lang>in</lang>, <lang>ref</lang>, or <lang>out</lang> to <lang>void*</lang>.</li>
+        /// </ul>
+        ///
+        /// Value types are not supported.
+        ///
+        /// Due to lack of variance for byrefs, returns involving byrefs are not supported. This
+        /// specifically means that accessors for fields of inaccessible types are not supported.
+        /// </remarks>
+        public UnsafeAccessorTypeAttribute(string typeName)
+        {
+            TypeName = typeName;
+        }
+
+        /// <summary>
+        /// Fully qualified or partially qualified type name to target.
+        /// </summary>
+        public string TypeName { get; }
+    }
+}
\ No newline at end of file