Fix native AOT crash in ReactorApplication at XAML bootstrap

[codemonkeychris]

Summary

Reactor-based WinUI apps published with PublishAot=true crashed at Application startup with STATUS_APPLICATION_INTERNAL_EXCEPTION (0xc000027b) inside Microsoft.UI.Xaml.dll. The faulting call was Resources.MergedDictionaries.Add(new XamlControlsResources()) in ReactorApplication.OnLaunched — under native AOT the runtime XAML parse path that programmatic construction triggers is not safe, whereas the same type loaded via an App.xaml-compiled XBF (as App.xaml-based projects do) is safe. This affected every consumer of ReactorApp.Run that published AOT.

Fix

• ReactorApplication.xaml (new) — Application-level XAML companion in the Reactor library that declares <XamlControlsResources/> in Application.Resources. The XAML compiler precompiles this to XBF and emits ReactorApplication.g.i.cs with InitializeComponent(), matching the pattern any App.xaml-based project uses.
• ReactorApp.cs — ReactorApplication constructor now calls InitializeComponent(); removed the programmatic new XamlControlsResources() from OnLaunched. GetXamlType delegates primarily to the XAML-compiler-generated Reactor_XamlTypeInfo.XamlMetaDataProvider (late-bound via Type.GetType with [DynamicDependency] to survive trimming), with a hand-rolled fallback.
• ReactorCoreXamlMetaDataProvider.cs (new) — fallback provider covering system primitives, core Microsoft.UI.Xaml types (DependencyObject, ResourceDictionary, Style, Setter, DataTemplate, …), enums referenced by theme-dictionary Setter values, and common value structs. Chained after the generated provider.

The late-bound Type.GetType for the generated provider is necessary because referencing Reactor_XamlTypeInfo.XamlMetaDataProvider directly would fail the C# pre-compile that the XAML compiler runs before generating that type — classic chicken-and-egg. The [DynamicDependency] attribute keeps the generated type alive under AOT trimming.

Benchmark

StressPerf.Reactor and StressPerf.ReactorGrid both previously crashed under AOT publish. Now both run cleanly end-to-end (ARM64, 7s per cell):

Variant	10% FPS	50% FPS	100% FPS	Avg update ms
WinUI.Reactor (AOT)	18.5	8.0	5.2	~0.1
WinUI.ReactorGrid (AOT)	12.6	8.8	7.0	~0.1

Update cost (~0.1 ms) is the lowest of any WinUI variant — Reactor's diffing layer + AOT is a good combination once it runs. Other AOT variants (Direct, DirectX) show small FPS wins and ~30-40 MB memory drops vs JIT builds.

Test plan

• dotnet publish -c Release -r win-arm64 succeeds for StressPerf.Reactor and StressPerf.ReactorGrid with 0 warnings
• Both published AOT binaries run to completion in --headless mode and write report files
• tests/stress_perf/run_bench_aot_publish.sh full 10/50/100% sweep passes for all 6 variants
• Verify non-AOT (JIT) builds still work unchanged
• Sanity check: launch an interactive (non-headless) Reactor app under AOT and confirm controls render with correct themes

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Addresses a native AOT startup crash for Reactor-based WinUI apps by shifting XamlControlsResources loading to the XAML-compiled (XBF) bootstrap path and adjusting XAML metadata provider delegation accordingly.

Changes:

• Adds ReactorApplication.xaml and calls InitializeComponent() to load <XamlControlsResources/> via XBF instead of programmatic construction.
• Updates ReactorApplication’s IXamlMetadataProvider implementation to prefer the XAML-compiler-generated provider (late-bound for trimming/AOT) with a fallback provider.
• Adds/updates stress perf AOT publish benchmarking script and result CSVs.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/stress_perf/run_bench_aot_publish.sh	New script to run 10/50/100% benchmarks against AOT-published outputs and emit CSV.
tests/stress_perf/benchmark_results_aot_publish.csv	Captures baseline results from the new AOT publish benchmark sweep.
tests/stress_perf/benchmark_results.csv	Updates the “current” benchmark results dataset.
src/Reactor/Hosting/ReactorCoreXamlMetaDataProvider.cs	Adds a fallback IXamlMetadataProvider for core primitives/enums/structs used during WinUI theme resource loading under AOT.
src/Reactor/Hosting/ReactorApplication.xaml	New application-level XAML that declares <XamlControlsResources/> in Application.Resources.
src/Reactor/Hosting/ReactorApp.cs	Switches to XAML-based resource bootstrap + generated metadata provider delegation; removes programmatic new XamlControlsResources() in OnLaunched.

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