PaulTrampert · Oct 4, 2026 · Oct 4, 2026
diff --git a/AGENTS.md b/AGENTS.md
@@ -11,15 +11,17 @@ omitted apart from one that was explicitly set to `null` or to a value. A contro
 
 ## Layout
 
-| Project | Target | Purpose |
-| --- | --- | --- |
-| `PTrampert.SimplePatch` | net8.0 | Core package: `Optional<T>`, `IPatchObject<T>`, `PatchClassBuilder`, JSON converters, validation |
-| `PTrampert.SimplePatch.Schema` | net8.0 | `PatchSchemaTransform`: the OpenAPI schema rewrite shared by both integration packages |
-| `PTrampert.SimplePatch.Swashbuckle` | net8.0 | Swashbuckle schema filter |
-| `PTrampert.SimplePatch.OpenApi` | net10.0 | `Microsoft.AspNetCore.OpenApi` schema transformer. It is net10.0 only because it needs `GetOrCreateSchemaAsync`. |
-| `*.Test` | match their subject | NUnit test projects, one per shipped package (except `Schema`, which the integration tests cover) |
-| `PTrampert.SimplePatch.Test.External` | net8.0 | A second assembly for the core tests, holding non-public types they use from another assembly. Not packed. |
-| `PTrampert.SimplePatch.Sample` | net8.0 | Sample web API, not packed |
+Every project targets `net10.0` only. Don't add another target framework without an issue for it.
+
+| Project | Purpose |
+| --- | --- |
+| `PTrampert.SimplePatch` | Core package: `Optional<T>`, `IPatchObject<T>`, `PatchClassBuilder`, JSON converters, validation |
+| `PTrampert.SimplePatch.Schema` | `PatchSchemaTransform`: the OpenAPI schema rewrite shared by both integration packages |
+| `PTrampert.SimplePatch.Swashbuckle` | Swashbuckle schema filter |
+| `PTrampert.SimplePatch.OpenApi` | `Microsoft.AspNetCore.OpenApi` schema transformer |
+| `*.Test` | NUnit test projects, one per shipped package (except `Schema`, which the integration tests cover) |
+| `PTrampert.SimplePatch.Test.External` | A second assembly for the core tests, holding non-public types they use from another assembly. Not packed. |
+| `PTrampert.SimplePatch.Sample` | Sample web API, not packed |
 
 Docs are built with docfx (`docfx.json`, `index.md`, `docs/`). The API reference is generated
 into `api/` from XML doc comments. `README.md` is packed into every NuGet package, so it is the

diff --git a/PTrampert.SimplePatch.OpenApi/PTrampert.SimplePatch.OpenApi.csproj b/PTrampert.SimplePatch.OpenApi/PTrampert.SimplePatch.OpenApi.csproj
@@ -1,11 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <!--
-          net10.0 only: the transformer needs OpenApiSchemaTransformerContext.GetOrCreateSchemaAsync
-          to obtain the source model's schema, which .NET 9 does not have. See the OpenAPI proposal
-          in docs/proposals for the .NET 9 story.
-        -->
         <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>

diff --git a/PTrampert.SimplePatch.Sample/PTrampert.SimplePatch.Sample.csproj b/PTrampert.SimplePatch.Sample/PTrampert.SimplePatch.Sample.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <Nullable>enable</Nullable>
         <ImplicitUsings>enable</ImplicitUsings>
     </PropertyGroup>

diff --git a/PTrampert.SimplePatch.Schema/PTrampert.SimplePatch.Schema.csproj b/PTrampert.SimplePatch.Schema/PTrampert.SimplePatch.Schema.csproj
@@ -1,11 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <!--
-          net8.0 so that both integration packages can consume it: PTrampert.SimplePatch.Swashbuckle
-          targets net8.0 and PTrampert.SimplePatch.OpenApi targets net10.0.
-        -->
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>

diff --git a/PTrampert.SimplePatch.Swashbuckle.Test/PTrampert.SimplePatch.Swashbuckle.Test.csproj b/PTrampert.SimplePatch.Swashbuckle.Test/PTrampert.SimplePatch.Swashbuckle.Test.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
 

diff --git a/PTrampert.SimplePatch.Swashbuckle/PTrampert.SimplePatch.Swashbuckle.csproj b/PTrampert.SimplePatch.Swashbuckle/PTrampert.SimplePatch.Swashbuckle.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>

diff --git a/PTrampert.SimplePatch.Test.External/PTrampert.SimplePatch.Test.External.csproj b/PTrampert.SimplePatch.Test.External/PTrampert.SimplePatch.Test.External.csproj
@@ -4,7 +4,7 @@
          non-public property type from an assembly that, unlike the test project, grants no access
          to the generated patch classes. -->
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <IsPackable>false</IsPackable>

diff --git a/PTrampert.SimplePatch.Test/PTrampert.SimplePatch.Test.csproj b/PTrampert.SimplePatch.Test/PTrampert.SimplePatch.Test.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
 

diff --git a/PTrampert.SimplePatch/Optional.cs b/PTrampert.SimplePatch/Optional.cs
@@ -37,7 +37,7 @@
    /// Default constructor for Optional.
    /// Initializes an Optional with no value, meaning HasValue will be false.
    /// </summary>
    public Optional()
    {
        HasValue = false;
    }
@@ -64,7 +64,6 @@
     /// <returns>True if the Optional has a value and the values are equal. False otherwise.</returns>
     public static bool operator ==(Optional<T> left, T right)
     {
-        ArgumentNullException.ThrowIfNull(left);
         if (!left.HasValue)
             return false;
         if (left.Value != null)

diff --git a/PTrampert.SimplePatch/PTrampert.SimplePatch.csproj b/PTrampert.SimplePatch/PTrampert.SimplePatch.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
@@ -27,8 +27,7 @@
 
     <ItemGroup>
       <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.14.0" />
-      <PackageReference Include="System.CodeDom" Version="9.0.8" />
-      <PackageReference Include="System.Text.Json" Version="9.0.8" />
+      <PackageReference Include="System.CodeDom" Version="10.0.12" />
     </ItemGroup>
 
 </Project>
diff --git a/README.md b/README.md
@@ -25,6 +25,11 @@ and your object contains additional properties besides `name`, PTrampert.SimpleP
 - Documents PATCH routes properly in OpenAPI, via optional Swashbuckle and
   `Microsoft.AspNetCore.OpenApi` integration packages.
 
+## Requirements
+
+Every package targets `net10.0`, so your application needs .NET 10 or later. The last releases that
+run on .NET 8 and .NET 9 are the 1.x line.
+
 ## Getting Started
 A full sample project is available in the [PTrampert.SimplePatch.Samples](./PTrampert.SimplePatch.Sample)
 * Install the library via NuGet:
@@ -167,7 +172,7 @@ dotnet add package PTrampert.SimplePatch.Swashbuckle
 builder.Services.AddSwaggerGen(options => options.AddSimplePatchSchemas());
 ```
 
-### Microsoft.AspNetCore.OpenApi (.NET 10+)
+### Microsoft.AspNetCore.OpenApi
 
 ```bash
 dotnet add package PTrampert.SimplePatch.OpenApi

diff --git a/docs/getting-started.md b/docs/getting-started.md
@@ -78,7 +78,7 @@ dotnet add package PTrampert.SimplePatch
    }));
    ```
 
-   On .NET 10 and later, `PTrampert.SimplePatch.OpenApi` does the same for the built-in generator:
+   `PTrampert.SimplePatch.OpenApi` does the same for the built-in generator:
 
    ```csharp
    builder.Services.AddOpenApi(options => options.AddSimplePatchSchemas());

diff --git a/docs/proposals/openapi-contract-generation.md b/docs/proposals/openapi-contract-generation.md
@@ -10,6 +10,10 @@ net9.0 as proposed in §3. Obtaining the source model's schema from a transforme
 have. Supporting .NET 9 would need a different mechanism, and .NET 9's OpenAPI.NET 1.6 object model
 would also fork the shared transform. Swashbuckle covers .NET 8 and 9 in the meantime.
 
+Since 2.0, every package targets net10.0 only
+([#76](https://github.com/PaulTrampert/PTrampert.SimplePatch/issues/76)), so the target frameworks
+in §3 and §4 describe the 1.x packages.
+
 ## 1. The problem
 
 A route that takes `[FromBody] IPatchObject<PersonWriteModel>` is documented from the