diff --git a/csharp/Directory.Build.props b/csharp/Directory.Build.props
index 05681a7..ae9e8d0 100644
--- a/csharp/Directory.Build.props
+++ b/csharp/Directory.Build.props
@@ -26,7 +26,7 @@
     <!-- Fallback version for any build that does NOT pass /p:Version (local dev, source/project
          references). Keep this >= every published release and every consumer's compiled reference
          so roll-forward always succeeds. Bump on each release alongside the git tag. -->
-    <Version Condition="'$(Version)' == ''">2.11.1</Version>
+    <Version Condition="'$(Version)' == ''">2.14.0</Version>
 
     <!-- AssemblyVersion / FileVersion track the package Version (strip any prerelease suffix such
          as -preview1; AssemblyVersion must be purely numeric). The CLR pads a 3-part value to
diff --git a/csharp/RocketWelder.SDK.Devices.Welding.Tests/Doubles.cs b/csharp/RocketWelder.SDK.Devices.Welding.Tests/Doubles.cs
new file mode 100644
index 0000000..3632dde
--- /dev/null
+++ b/csharp/RocketWelder.SDK.Devices.Welding.Tests/Doubles.cs
@@ -0,0 +1,45 @@
+using ModelingEvolution.Drawing;
+using ModelingEvolution.Signals;
+using RocketWelder.SDK.Abstractions;
+
+namespace RocketWelder.SDK.Devices.Welding.Tests;
+
+/// <summary>
+/// Implements <see cref="IWeldingMachine"/> without overriding any of the wire-inch surface, so
+/// <c>CanWireInch</c>/<c>WireInchSignal</c>/<c>WireInch</c>/<c>WireInchOn</c>/<c>WireInchOff</c>
+/// resolve to the interface's default implementations (design.md "SDK — IWeldingMachine delta").
+/// </summary>
+internal sealed class UnsupportedWeldingMachine : IWeldingMachine
+{
+    private static WritableSignal<T> Signal<T>(string name) =>
+        new(new SignalMetadata(name, new Uri($"signal://test/{name}"), null, null));
+
+    public DeviceId Id { get; } = new("test-welder", Guid.Empty);
+    public bool IsConnected { get; init; }
+
+    public ISignal<Amps<float>> CurrentSignal { get; } = Signal<Amps<float>>("current");
+    public ISignal<Amps<float>> TargetCurrentSignal { get; } = Signal<Amps<float>>("target-current");
+    public ISignal<Speed<float>> WireFeedSpeedSignal { get; } = Signal<Speed<float>>("wire-feed-speed");
+    public ISignal<Volts<float>> WeldingVoltageSignal { get; } = Signal<Volts<float>>("welding-voltage");
+
+    public WritableSignal<WeldingMode> ModeSignal { get; } = Signal<WeldingMode>("mode");
+    public WeldingMode Mode { get; set; }
+
+    public WritableSignal<bool> WeldingStartSignal { get; } = Signal<bool>("welding-start");
+    public bool WeldingStart { get; set; }
+
+    public WritableSignal<bool> GasSignal { get; } = Signal<bool>("gas");
+    public bool Gas { get; set; }
+
+    public WritableSignal<int> JobNumberSignal { get; } = Signal<int>("job-number");
+    public int JobNumber { get; set; }
+
+    public ValueTask ArcOn() => throw new NotSupportedException();
+    public ValueTask ArcOff() => ValueTask.CompletedTask;
+    public ValueTask GasOn() => throw new NotSupportedException();
+    public ValueTask GasOff() => ValueTask.CompletedTask;
+
+    public void Dispose()
+    {
+    }
+}
diff --git a/csharp/RocketWelder.SDK.Devices.Welding.Tests/RocketWelder.SDK.Devices.Welding.Tests.csproj b/csharp/RocketWelder.SDK.Devices.Welding.Tests/RocketWelder.SDK.Devices.Welding.Tests.csproj
new file mode 100644
index 0000000..2a5ad9b
--- /dev/null
+++ b/csharp/RocketWelder.SDK.Devices.Welding.Tests/RocketWelder.SDK.Devices.Welding.Tests.csproj
@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="FluentAssertions" Version="6.12.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.5.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\RocketWelder.SDK.Devices.Welding\RocketWelder.SDK.Devices.Welding.csproj" />
+  </ItemGroup>
+
+</Project>
diff --git a/csharp/RocketWelder.SDK.Devices.Welding.Tests/WireInchDefaultsTests.cs b/csharp/RocketWelder.SDK.Devices.Welding.Tests/WireInchDefaultsTests.cs
new file mode 100644
index 0000000..8d37291
--- /dev/null
+++ b/csharp/RocketWelder.SDK.Devices.Welding.Tests/WireInchDefaultsTests.cs
@@ -0,0 +1,46 @@
+using FluentAssertions;
+
+namespace RocketWelder.SDK.Devices.Welding.Tests;
+
+/// <summary>
+/// design.md "SDK — IWeldingMachine delta" / test-scenarios.md U-01..U-03: the wire-inch surface's
+/// default interface members, exercised through an implementation that overrides none of them.
+/// </summary>
+public class WireInchDefaultsTests
+{
+    [Fact]
+    public void CanWireInch_Should_Be_False_On_An_Unsupported_Welder()
+    {
+        // Arrange
+        IWeldingMachine welder = new UnsupportedWeldingMachine();
+
+        // Act & Assert
+        welder.CanWireInch.Should().BeFalse();
+    }
+
+    [Fact]
+    public async Task WireInchOn_Should_Throw_NotSupportedException_On_An_Unsupported_Welder()
+    {
+        // Arrange
+        IWeldingMachine welder = new UnsupportedWeldingMachine();
+
+        // Act
+        var act = () => welder.WireInchOn().AsTask();
+
+        // Assert
+        await act.Should().ThrowAsync<NotSupportedException>();
+    }
+
+    [Fact]
+    public async Task WireInchOff_Should_Complete_Without_Throwing_When_Unsupported_And_Disconnected()
+    {
+        // Arrange
+        IWeldingMachine welder = new UnsupportedWeldingMachine { IsConnected = false };
+
+        // Act
+        var act = () => welder.WireInchOff().AsTask();
+
+        // Assert
+        await act.Should().NotThrowAsync();
+    }
+}
diff --git a/csharp/RocketWelder.SDK.Devices.Welding/IWeldingMachine.cs b/csharp/RocketWelder.SDK.Devices.Welding/IWeldingMachine.cs
index f5c4c71..a18610c 100644
--- a/csharp/RocketWelder.SDK.Devices.Welding/IWeldingMachine.cs
+++ b/csharp/RocketWelder.SDK.Devices.Welding/IWeldingMachine.cs
@@ -149,4 +149,19 @@ public interface IWeldingMachine : IDevice
 
     /// <summary>Close the shielding-gas valve. Returns when the hardware has acknowledged the command.</summary>
     ValueTask GasOff();
+
+    /// <summary>Whether this welder can feed wire out of the torch. UI gate; defaults to unsupported.</summary>
+    bool CanWireInch => false;
+
+    /// <summary>Wire-inch held level, shaped like <see cref="GasSignal"/>. Defaults to unsupported.</summary>
+    WritableSignal<bool> WireInchSignal => throw new NotSupportedException();
+
+    /// <summary>Plain ergonomic surface. Defaults to unsupported (false / throws); an override forwards to <see cref="WireInchSignal"/>.</summary>
+    bool WireInch { get => false; set => throw new NotSupportedException(); }
+
+    /// <summary>Engage wire feed. Throws <see cref="NotSupportedException"/> when unsupported.</summary>
+    ValueTask WireInchOn() => throw new NotSupportedException();
+
+    /// <summary>Disengage wire feed. Idempotent and never throws, connected or not.</summary>
+    ValueTask WireInchOff() => ValueTask.CompletedTask;
 }
diff --git a/csharp/RocketWelder.SDK.sln b/csharp/RocketWelder.SDK.sln
index 098dd3a..c58e91f 100644
--- a/csharp/RocketWelder.SDK.sln
+++ b/csharp/RocketWelder.SDK.sln
@@ -84,6 +84,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "RocketWelder.SDK.Devices.Mo
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "RocketWelder.SDK.Devices.Motion.Tests", "RocketWelder.SDK.Devices.Motion.Tests\RocketWelder.SDK.Devices.Motion.Tests.csproj", "{30189920-72B0-41AE-9B2A-E49C7A7071DB}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "RocketWelder.SDK.Devices.Welding.Tests", "RocketWelder.SDK.Devices.Welding.Tests\RocketWelder.SDK.Devices.Welding.Tests.csproj", "{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -514,6 +516,18 @@ Global
 		{30189920-72B0-41AE-9B2A-E49C7A7071DB}.Release|x64.Build.0 = Release|Any CPU
 		{30189920-72B0-41AE-9B2A-E49C7A7071DB}.Release|x86.ActiveCfg = Release|Any CPU
 		{30189920-72B0-41AE-9B2A-E49C7A7071DB}.Release|x86.Build.0 = Release|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Debug|x64.Build.0 = Debug|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Debug|x86.Build.0 = Debug|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Release|Any CPU.Build.0 = Release|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Release|x64.ActiveCfg = Release|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Release|x64.Build.0 = Release|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Release|x86.ActiveCfg = Release|Any CPU
+		{5F8278F0-C070-4CCB-83FD-D9AB4F3DE798}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE