diff --git a/.github/workflows/uixrender-ci.yml b/.github/workflows/uixrender-ci.yml
new file mode 100644
index 0000000..0dc0299
--- /dev/null
+++ b/.github/workflows/uixrender-ci.yml
@@ -0,0 +1,37 @@
+name: UIXrender CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    # UIXrender/UIXsup are implemented cross-platform (Silk.NET, no Windows-specific
+    # APIs), but NativeAOT can't cross-compile Linux->Windows, and the P/Invoke-based
+    # managed consumers we need to stay compatible with (UIX.dll et al) only run on
+    # Windows today -- so Windows is what Phase 0 verifies against here. Other RIDs can
+    # get their own job later once there's something worth publishing them for.
+    runs-on: windows-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "8.0.x"
+
+      - name: Restore
+        run: dotnet restore MicrosoftIris.sln
+
+      - name: Build solution
+        run: dotnet build MicrosoftIris.sln -c Release --no-restore
+
+      - name: Publish UIXrender (NativeAOT, win-x64)
+        run: dotnet publish UIXrender/UIXrender.csproj -c Release -f net8.0 -r win-x64 --self-contained -p:PublishAot=true
+
+      - name: Publish UIXsup (NativeAOT, win-x64)
+        run: dotnet publish UIXsup/UIXsup.csproj -c Release -f net8.0 -r win-x64 --self-contained -p:PublishAot=true
+
+      # TODO: run the Windows-only interop test harness (Tests/UIXrender.Interop.Tests)
+      # against the published DLLs once it exists (Phase 0 spike step) — see
+      # logs/UIXrender/Architecture.md and the plan for context.
diff --git a/Directory.Build.props b/Directory.Build.props
index 18e8638..668cdda 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -19,7 +19,9 @@
     </PropertyGroup>
 
     <PropertyGroup Condition=" $([MSBuild]::IsOsPlatform('Windows')) ">
-        <TargetFrameworks>$(TargetFrameworks);net461;net8.0-windows10.0.22000</TargetFrameworks>
+        <TargetFrameworks>$(TargetFrameworks);net8.0-windows10.0.22000</TargetFrameworks>
+        
+        <TargetFrameworks Condition=" $(EnableNetFXTarget) == 'true' ">$(TargetFrameworks);net461;</TargetFrameworks>
     </PropertyGroup>
 
     <Choose>
diff --git a/UIX.RenderApi/UIX.RenderApi.csproj b/UIX.RenderApi/UIX.RenderApi.csproj
index c2af7a6..36eadfb 100644
--- a/UIX.RenderApi/UIX.RenderApi.csproj
+++ b/UIX.RenderApi/UIX.RenderApi.csproj
@@ -7,5 +7,7 @@
         <RootNamespace></RootNamespace>
         <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+        
+        <EnableNetFXTarget>true</EnableNetFXTarget>
     </PropertyGroup>
 </Project>
\ No newline at end of file
diff --git a/UIX/UIX.csproj b/UIX/UIX.csproj
index 43fcc1a..8367b91 100644
--- a/UIX/UIX.csproj
+++ b/UIX/UIX.csproj
@@ -7,6 +7,8 @@
         <RootNamespace></RootNamespace>
         <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+
+        <EnableNetFXTarget>true</EnableNetFXTarget>
     </PropertyGroup>
 
     <ItemGroup>
diff --git a/UIXrender/UIXrender.csproj b/UIXrender/UIXrender.csproj
index 8db8e17..3357bf2 100644
--- a/UIXrender/UIXrender.csproj
+++ b/UIXrender/UIXrender.csproj
@@ -6,5 +6,12 @@
         <RootNamespace>Microsoft.Iris.Render</RootNamespace>
         <GenerateAssemblyInfo>true</GenerateAssemblyInfo>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+
+        <PublishAot>true</PublishAot>
+
+        <!-- Required for PublishAot to emit an actual exporting shared library (.dll/.so)
+             for the [UnmanagedCallersOnly] methods below: without this, PublishAot
+             alone produces a native executable, not something P/Invoke-able. -->
+        <NativeLib>Shared</NativeLib>
     </PropertyGroup>
 </Project>
\ No newline at end of file
diff --git a/UIXsup/DebugCategory.cs b/UIXsup/DebugCategory.cs
new file mode 100644
index 0000000..8ef3be9
--- /dev/null
+++ b/UIXsup/DebugCategory.cs
@@ -0,0 +1,48 @@
+namespace Microsoft.Iris.Support;
+
+// Mirrors Microsoft.Iris.Render.DebugCategory (UIX.RenderApi/Microsoft/Iris/Render/DebugCategory.cs)
+// field-for-field: ordinal values are part of the wire contract with the already-shipped
+// managed callers (DebugGetCategoryLevel/DebugSetCategoryLevel pass this by value), so
+// the order here must match exactly, not just the names.
+public enum DebugCategory
+{
+    Animation,
+    Critical,
+    Deprecated,
+    Dispatcher,
+    Dump,
+    Dx9Wrapper,
+    DynamicSurface,
+    Failure,
+    FormWindow,
+    GraphicsCache,
+    IFC,
+    ObjectCache,
+    Performance,
+    Profile,
+    Queues,
+    Render,
+    Sounds,
+    Surface,
+    SurfacePool,
+    SurfaceRestoration,
+    Timeouts,
+    Transport,
+    WindowState,
+    Effect,
+    HTTP,
+    ExternalCount,
+    Protocol,
+    RenderHost,
+    DumpException,
+    Focus,
+    Input,
+    TreeDisposal,
+    VisualSizePos,
+    Visual,
+    Painting,
+    RenderWindow,
+    ImageLoad,
+    ImageCache,
+    TotalCount,
+}
diff --git a/UIXsup/DebugState.cs b/UIXsup/DebugState.cs
new file mode 100644
index 0000000..4199d6a
--- /dev/null
+++ b/UIXsup/DebugState.cs
@@ -0,0 +1,22 @@
+namespace Microsoft.Iris.Support;
+
+internal static class DebugState
+{
+    private static readonly byte[] s_categoryLevels = new byte[(int)DebugCategory.TotalCount];
+
+    public static bool TimedWriteLines { get; set; }
+    public static string WriteLinePrefix { get; set; } = string.Empty;
+
+    public static byte GetCategoryLevel(DebugCategory category)
+    {
+        int index = (int)category;
+        return (uint)index < (uint)s_categoryLevels.Length ? s_categoryLevels[index] : (byte)0;
+    }
+
+    public static void SetCategoryLevel(DebugCategory category, byte level)
+    {
+        int index = (int)category;
+        if ((uint)index < (uint)s_categoryLevels.Length)
+            s_categoryLevels[index] = level;
+    }
+}
diff --git a/UIXsup/Interop/DebugApi.cs b/UIXsup/Interop/DebugApi.cs
new file mode 100644
index 0000000..2c14ebb
--- /dev/null
+++ b/UIXsup/Interop/DebugApi.cs
@@ -0,0 +1,38 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Iris.Support.Interop;
+
+// [UnmanagedCallersOnly] exports matching the 5 DllImport("UIXsup.dll") declarations in
+// the already-shipped managed callers (eDebugApi.cs / DebugHelpers.cs) field-for-field.
+// See logs/UIXrender/UIXsup.md for why parameters are byte*/int here instead of
+// string/bool (ANSI marshaling, blittability) and for the DebugDisplayErrorStack scope
+// gap noted below.
+public static unsafe class DebugApi
+{
+    [UnmanagedCallersOnly(EntryPoint = "DebugDisplayErrorStack")]
+    public static int DebugDisplayErrorStack(byte* stMessage, byte* filename, int line, byte* title, byte* stackTrace)
+    {
+        string timestamp = DebugState.TimedWriteLines ? $"[{DateTime.Now:HH:mm:ss.fff}] " : string.Empty;
+        Console.Error.WriteLine(
+            $"{timestamp}{DebugState.WriteLinePrefix}{PtrToString(title)}: {PtrToString(stMessage)} ({PtrToString(filename)}:{line})\n{PtrToString(stackTrace)}");
+
+        // TODO: no interactive dialog UI yet (see logs/UIXrender/UIXsup.md) -- always
+        // reports "don't break".
+        return 0;
+    }
+
+    [UnmanagedCallersOnly(EntryPoint = "DebugSetTimedWriteLines")]
+    public static void DebugSetTimedWriteLines(int fEnabled) => DebugState.TimedWriteLines = fEnabled != 0;
+
+    [UnmanagedCallersOnly(EntryPoint = "DebugSetWriteLinePrefix")]
+    public static void DebugSetWriteLinePrefix(byte* stPrefix) => DebugState.WriteLinePrefix = PtrToString(stPrefix) ?? string.Empty;
+
+    [UnmanagedCallersOnly(EntryPoint = "DebugGetCategoryLevel")]
+    public static byte DebugGetCategoryLevel(DebugCategory cat) => DebugState.GetCategoryLevel(cat);
+
+    [UnmanagedCallersOnly(EntryPoint = "DebugSetCategoryLevel")]
+    public static void DebugSetCategoryLevel(DebugCategory cat, byte level) => DebugState.SetCategoryLevel(cat, level);
+
+    private static string PtrToString(byte* p) => p == null ? null : Marshal.PtrToStringAnsi((IntPtr)p);
+}
diff --git a/UIXsup/UIXsup.csproj b/UIXsup/UIXsup.csproj
index 42f5411..ac9951d 100644
--- a/UIXsup/UIXsup.csproj
+++ b/UIXsup/UIXsup.csproj
@@ -6,5 +6,12 @@
         <RootNamespace>Microsoft.Iris.Support</RootNamespace>
         <GenerateAssemblyInfo>true</GenerateAssemblyInfo>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+
+        <PublishAot>true</PublishAot>
+
+        <!-- Required for PublishAot to emit an actual exporting shared library (.dll/.so)
+             for the [UnmanagedCallersOnly] methods below: without this, PublishAot
+             alone produces a native executable, not something P/Invoke-able. -->
+        <NativeLib>Shared</NativeLib>
     </PropertyGroup>
 </Project>
\ No newline at end of file