diff --git a/.gitignore b/.gitignore
index 9960f95..036b9c9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,8 @@
 build/
 build-x86/
 build-arm64/
+tests/apps/WinUI3Sample/bin/
+tests/apps/WinUI3Sample/obj/
 
 # IDE files
 .vs/
diff --git a/CMakeLists.txt b/CMakeLists.txt
index cc1ea7f..455ba4b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -303,6 +303,32 @@ add_custom_target(wpf_sample_app ALL
 file(TO_NATIVE_PATH "${WPF_SAMPLE_OUTPUT_DIR}/WpfSample.exe" WPF_SAMPLE_EXE_NATIVE)
 string(REPLACE "\\" "\\\\" WPF_SAMPLE_EXE_ESCAPED "${WPF_SAMPLE_EXE_NATIVE}")
 
+# WinUI3 sample app used by integration tests
+set(WINUI3_SAMPLE_PROJECT "${CMAKE_SOURCE_DIR}/tests/apps/WinUI3Sample/WinUI3Sample.csproj")
+set(WINUI3_SAMPLE_OUTPUT_DIR "${CMAKE_BINARY_DIR}/tests/apps/WinUI3Sample")
+set(WINUI3_SAMPLE_MSBUILD_ARGS "")
+if(DEFINED ENV{VSINSTALLDIR} AND EXISTS "$ENV{VSINSTALLDIR}/MSBuild/Microsoft/VisualStudio/v18.0/AppxPackage/Microsoft.Build.Packaging.Pri.Tasks.dll")
+    list(APPEND WINUI3_SAMPLE_MSBUILD_ARGS
+        "-p:MSBuildExtensionsPath=$ENV{VSINSTALLDIR}/MSBuild")
+endif()
+add_custom_target(winui3_sample_app ALL
+    COMMAND dotnet publish "${WINUI3_SAMPLE_PROJECT}"
+        -c Release -p:Platform=x64 -r win-x64 --self-contained true
+        -o "${WINUI3_SAMPLE_OUTPUT_DIR}"
+        ${WINUI3_SAMPLE_MSBUILD_ARGS}
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different
+        "${CMAKE_SOURCE_DIR}/tests/apps/WinUI3Sample/obj/x64/Release/net10.0-windows10.0.19041.0/win-x64/App.xbf"
+        "${WINUI3_SAMPLE_OUTPUT_DIR}/App.xbf"
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different
+        "${CMAKE_SOURCE_DIR}/tests/apps/WinUI3Sample/obj/x64/Release/net10.0-windows10.0.19041.0/win-x64/MainWindow.xbf"
+        "${WINUI3_SAMPLE_OUTPUT_DIR}/MainWindow.xbf"
+    BYPRODUCTS "${WINUI3_SAMPLE_OUTPUT_DIR}/WinUI3Sample.exe"
+    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+    COMMENT "Publishing WinUI3 sample app"
+)
+file(TO_NATIVE_PATH "${WINUI3_SAMPLE_OUTPUT_DIR}/WinUI3Sample.exe" WINUI3_SAMPLE_EXE_NATIVE)
+string(REPLACE "\\" "\\\\" WINUI3_SAMPLE_EXE_ESCAPED "${WINUI3_SAMPLE_EXE_NATIVE}")
+
 # Integration tests — require a running Notepad instance
 add_executable(lvt_integration_tests
     tests/integration_tests.cpp
@@ -312,6 +338,7 @@ target_include_directories(lvt_integration_tests PRIVATE src)
 target_compile_definitions(lvt_integration_tests PRIVATE
     WIN32_LEAN_AND_MEAN NOMINMAX WINRT_LEAN_AND_MEAN UNICODE _UNICODE
     WPF_SAMPLE_EXE_PATH="${WPF_SAMPLE_EXE_ESCAPED}"
+    WINUI3_SAMPLE_EXE_PATH="${WINUI3_SAMPLE_EXE_ESCAPED}"
 )
 target_link_libraries(lvt_integration_tests PRIVATE
     GTest::gtest GTest::gtest_main
@@ -319,7 +346,7 @@ target_link_libraries(lvt_integration_tests PRIVATE
     comctl32
 )
 target_link_options(lvt_integration_tests PRIVATE "/MANIFEST:NO")
-add_dependencies(lvt_integration_tests wpf_sample_app)
+add_dependencies(lvt_integration_tests wpf_sample_app winui3_sample_app)
 add_test(NAME integration_tests COMMAND lvt_integration_tests)
 
 # Chromium plugin tests — DOM JSON format and native messaging protocol
diff --git a/tests/apps/WinUI3Sample/App.xaml b/tests/apps/WinUI3Sample/App.xaml
new file mode 100644
index 0000000..74ab9ee
--- /dev/null
+++ b/tests/apps/WinUI3Sample/App.xaml
@@ -0,0 +1,5 @@
+<Application
+    x:Class="WinUI3Sample.App"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+</Application>
diff --git a/tests/apps/WinUI3Sample/App.xaml.cs b/tests/apps/WinUI3Sample/App.xaml.cs
new file mode 100644
index 0000000..49a4f44
--- /dev/null
+++ b/tests/apps/WinUI3Sample/App.xaml.cs
@@ -0,0 +1,19 @@
+using Microsoft.UI.Xaml;
+
+namespace WinUI3Sample;
+
+public partial class App : Application
+{
+    private Window? window;
+
+    public App()
+    {
+        InitializeComponent();
+    }
+
+    protected override void OnLaunched(LaunchActivatedEventArgs args)
+    {
+        window = new MainWindow();
+        window.Activate();
+    }
+}
diff --git a/tests/apps/WinUI3Sample/MainWindow.xaml b/tests/apps/WinUI3Sample/MainWindow.xaml
new file mode 100644
index 0000000..c38fb40
--- /dev/null
+++ b/tests/apps/WinUI3Sample/MainWindow.xaml
@@ -0,0 +1,20 @@
+<Window
+    x:Class="WinUI3Sample.MainWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    Title="LVT WinUI3 Sample">
+
+    <Grid x:Name="RootGrid" Padding="24" RowSpacing="12" Width="420" Height="260">
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="Auto" />
+        </Grid.RowDefinitions>
+
+        <TextBlock x:Name="HeaderText" Text="LVT WinUI3 Sample" FontSize="24" />
+        <TextBox x:Name="InputBox" Grid.Row="1" Header="Sample input" Text="Durable key text" />
+        <Button x:Name="PrimaryButton" Grid.Row="2" Content="Primary action" />
+        <CheckBox x:Name="ReadyCheckBox" Grid.Row="3" Content="Ready" IsChecked="True" />
+    </Grid>
+</Window>
diff --git a/tests/apps/WinUI3Sample/MainWindow.xaml.cs b/tests/apps/WinUI3Sample/MainWindow.xaml.cs
new file mode 100644
index 0000000..b5164a0
--- /dev/null
+++ b/tests/apps/WinUI3Sample/MainWindow.xaml.cs
@@ -0,0 +1,12 @@
+using Microsoft.UI.Xaml;
+
+namespace WinUI3Sample;
+
+public sealed partial class MainWindow : Window
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+        Title = "LVT WinUI3 Sample";
+    }
+}
diff --git a/tests/apps/WinUI3Sample/WinUI3Sample.csproj b/tests/apps/WinUI3Sample/WinUI3Sample.csproj
new file mode 100644
index 0000000..ad74b48
--- /dev/null
+++ b/tests/apps/WinUI3Sample/WinUI3Sample.csproj
@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net10.0-windows10.0.19041.0</TargetFramework>
+    <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
+    <RootNamespace>WinUI3Sample</RootNamespace>
+    <AssemblyName>WinUI3Sample</AssemblyName>
+    <Nullable>enable</Nullable>
+    <UseWinUI>true</UseWinUI>
+    <WindowsPackageType>None</WindowsPackageType>
+    <WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>
+    <Platforms>x64</Platforms>
+    <PlatformTarget>x64</PlatformTarget>
+    <RuntimeIdentifier>win-x64</RuntimeIdentifier>
+    <RuntimeIdentifiers>win-x64</RuntimeIdentifiers>
+    <SelfContained>true</SelfContained>
+    <UseRidGraph>true</UseRidGraph>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.WindowsAppSDK" Version="2.2.0" />
+  </ItemGroup>
+</Project>
diff --git a/tests/integration_tests.cpp b/tests/integration_tests.cpp
index 97298d7..c2193e4 100644
--- a/tests/integration_tests.cpp
+++ b/tests/integration_tests.cpp
@@ -402,6 +402,47 @@ static bool frameworks_contain_wpf(const json& j) {
     return false;
 }
 
+static bool frameworks_contain_winui3(const json& j) {
+    if (!j.contains("frameworks") || !j["frameworks"].is_array())
+        return false;
+    for (auto& fw : j["frameworks"]) {
+        if (fw.is_string() && fw.get<std::string>().starts_with("winui3"))
+            return true;
+    }
+    return false;
+}
+
+static bool has_winui3_descendant(const json& el) {
+    if (el.value("framework", "") == "winui3")
+        return true;
+
+    if (el.contains("children") && el["children"].is_array()) {
+        for (auto& child : el["children"]) {
+            if (has_winui3_descendant(child))
+                return true;
+        }
+    }
+    return false;
+}
+
+static bool has_winui3_stitched_under_bridge(const json& el) {
+    if (el.value("className", "") == "Microsoft.UI.Content.DesktopChildSiteBridge" &&
+        el.contains("children") && el["children"].is_array()) {
+        for (auto& child : el["children"]) {
+            if (has_winui3_descendant(child))
+                return true;
+        }
+    }
+
+    if (el.contains("children") && el["children"].is_array()) {
+        for (auto& child : el["children"]) {
+            if (has_winui3_stitched_under_bridge(child))
+                return true;
+        }
+    }
+    return false;
+}
+
 static const json* find_element_by_type_property(const json& el,
                                                  const std::string& type,
                                                  const std::string& property,
@@ -539,6 +580,129 @@ TEST_F(WpfSampleFixture, DurableKeyContract) {
     EXPECT_EQ(queried.value("framework", ""), "wpf");
     EXPECT_EQ(queried.value("name", ""), "OkButton");
 }
+
+class WinUI3SampleFixture : public ::testing::Test {
+protected:
+    static void SetUpTestSuite() {
+        s_sample_exe = WINUI3_SAMPLE_EXE_PATH;
+        if (!fs::exists(s_sample_exe)) {
+            s_skip_reason = "WinUI3 sample app not found: " + s_sample_exe;
+            return;
+        }
+
+        STARTUPINFOA si = {sizeof(si)};
+        s_pi = {};
+        auto workdir = fs::path(s_sample_exe).parent_path().string();
+        std::string cmd = "\"" + s_sample_exe + "\"";
+        if (!CreateProcessA(nullptr, cmd.data(), nullptr, nullptr, FALSE, 0,
+                            nullptr, workdir.c_str(), &si, &s_pi)) {
+            s_skip_reason = "Failed to launch WinUI3 sample app";
+            return;
+        }
+        s_pid = s_pi.dwProcessId;
+        if (s_pi.hProcess) {
+            WaitForInputIdle(s_pi.hProcess, 10000);
+        }
+
+        auto lvt = get_lvt_path();
+        for (int attempt = 0; attempt < 60; ++attempt) {
+            if (WaitForSingleObject(s_pi.hProcess, 0) == WAIT_OBJECT_0) {
+                s_skip_reason = "WinUI3 sample app exited before it became ready";
+                return;
+            }
+
+            auto output = run_command(make_cmd(lvt, get_pid_arg()));
+            auto j = json::parse(output, nullptr, false);
+            if (!j.is_discarded() && frameworks_contain_winui3(j) &&
+                j.contains("root") &&
+                json_tree_has_named_control(j["root"], "PrimaryButton") &&
+                json_tree_has_named_control(j["root"], "InputBox") &&
+                json_tree_has_named_control(j["root"], "ReadyCheckBox")) {
+                s_ready = true;
+                return;
+            }
+            Sleep(1000);
+        }
+
+        s_skip_reason = "WinUI3 sample app never became ready with WinUI3 framework and named controls";
+    }
+
+    static void TearDownTestSuite() {
+        if (s_pi.hProcess) {
+            TerminateProcess(s_pi.hProcess, 0);
+            CloseHandle(s_pi.hProcess);
+            CloseHandle(s_pi.hThread);
+        }
+    }
+
+    static void SkipIfNotReady() {
+        if (!s_ready)
+            GTEST_SKIP() << s_skip_reason;
+    }
+
+    static std::string get_pid_arg() {
+        return "--pid " + std::to_string(s_pid);
+    }
+
+    static PROCESS_INFORMATION s_pi;
+    static DWORD s_pid;
+    static bool s_ready;
+    static std::string s_sample_exe;
+    static std::string s_skip_reason;
+};
+
+PROCESS_INFORMATION WinUI3SampleFixture::s_pi = {};
+DWORD WinUI3SampleFixture::s_pid = 0;
+bool WinUI3SampleFixture::s_ready = false;
+std::string WinUI3SampleFixture::s_sample_exe;
+std::string WinUI3SampleFixture::s_skip_reason;
+
+TEST_F(WinUI3SampleFixture, DurableKeysDeterministicAndQueryable) {
+    SkipIfNotReady();
+
+    auto lvt = get_lvt_path();
+    auto first = run_command(make_cmd(lvt, get_pid_arg()));
+    auto second = run_command(make_cmd(lvt, get_pid_arg()));
+    ASSERT_FALSE(first.empty());
+    ASSERT_FALSE(second.empty());
+
+    auto j1 = json::parse(first, nullptr, false);
+    auto j2 = json::parse(second, nullptr, false);
+    ASSERT_FALSE(j1.is_discarded());
+    ASSERT_FALSE(j2.is_discarded());
+    ASSERT_TRUE(frameworks_contain_winui3(j1));
+    ASSERT_TRUE(has_winui3_stitched_under_bridge(j1["root"]))
+        << "WinUI3 elements were not grafted under DesktopChildSiteBridge";
+
+    std::vector<const json*> elements;
+    collect_json_elements(j1["root"], elements);
+    ASSERT_GT(elements.size(), 0u);
+
+    std::set<std::string> keys;
+    for (auto* el : elements) {
+        auto key = el->value("key", "");
+        EXPECT_FALSE(key.empty()) << "Element " << el->value("id", "?") << " has empty durable key";
+        EXPECT_TRUE(keys.insert(key).second) << "Duplicate durable key: " << key;
+    }
+
+    std::map<std::string, std::string> firstMap;
+    std::map<std::string, std::string> secondMap;
+    collect_key_contract_map(j1["root"], "0", firstMap);
+    collect_key_contract_map(j2["root"], "0", secondMap);
+    EXPECT_EQ(firstMap, secondMap);
+
+    auto* button = find_named_control(j1["root"], "PrimaryButton");
+    ASSERT_NE(button, nullptr);
+    EXPECT_EQ(button->value("framework", ""), "winui3");
+    EXPECT_EQ(button->value("type", ""), "Button");
+
+    auto buttonKey = button->value("key", "");
+    ASSERT_FALSE(buttonKey.empty());
+    auto byKey = run_command(make_cmd(lvt, get_pid_arg() + " --query " +
+                                           cmd_escape_arg(buttonKey) + " name"));
+    EXPECT_EQ(trim_crlf(byKey), "PrimaryButton");
+}
+
 TEST_F(NotepadFixture, Win32BoundsReasonable) {
     // Every element in the Win32 tree should have reasonable (non-extreme) bounds
     auto lvt = get_lvt_path();