Windows portable-core and Swift/WinRT projection host

This is a Windows-only developer build surface for Context for Claude. It has two deliberately separate boundaries:

1. ../core is the portable C++17 policy/audio/recall library. Native Windows hosts call its stable C ABI directly.
2. swift-winrt at pinned revision 79ffa65c generates Swift bindings for Windows SDK metadata (.winmd). It is not a generator for this project's C ABI and does not make the core into a WinRT component.

The CMake target generate_windows_foundation_projection runs the actual upstream swiftwinrt.exe against the installed SDK's Windows.winmd, including the concrete Windows.Foundation namespace. It produces the real platform projection that the Swift host in swift-host/ consumes.

The swift-host/ directory is a SwiftPM package that imports the generated WindowsFoundation projection and links the portable C++ core through a module map (CContextCore). The CMake target build_swift_host generates the projection into swift-host/projection/ and then runs swift build to compile the host executable.

What this proves

• The portable core builds and its C++ host callers work on Windows.
• The pinned upstream Swift/WinRT generator can project a real Windows SDK namespace.
• A Swift host can import that projection and link the C++ core through a C ABI module map.
• The host boundary is honest: Windows APIs use generated Swift/WinRT bindings; product policy/audio/recall use the Context core C ABI.

What this does not implement

This slice does not ship a Windows app, microphone/system-audio capture, screen capture, OCR, storage, MCP, or the macOS menu-bar UI. The Swift host in swift-host/ proves the import/link boundary but does not implement capture or MCP. In particular, SwiftUI is not provided by Swift/WinRT and is not claimed to be a supported Windows UI stack here. A Windows UI must choose and validate its own native UI layer (for example WinUI) before this becomes an end-user host.

Prerequisites

• Windows 10/11 on x64 or ARM64.
• Visual Studio 2022 with the Desktop development with C++ workload and a Windows SDK.
• A Windows Swift toolchain compatible with the pinned swift-winrt revision. Upstream recommends using the release selected by its Windows build workflow.
• CMake 3.24+ and Git.

Run configuration from a Visual Studio Developer PowerShell so WindowsSdkDir and WindowsSDKVersion resolve the SDK's UnionMetadata/.../Windows.winmd file. CMake validates this before downloading/building the generator.

Validate on Windows

# Configure native core host + the pinned upstream Swift/WinRT generator.
cmake -S desktop/context-for-claude/windows -B out/context-for-claude-windows `
  -G "Visual Studio 17 2022" -A x64

# Portable-core host checks.
cmake --build out/context-for-claude-windows --config Release
ctest --test-dir out/context-for-claude-windows -C Release --output-on-failure

# Real upstream Windows metadata -> Swift projection.
cmake --build out/context-for-claude-windows --config Release `
  --target generate_windows_foundation_projection

# Swift host: generates the WinRT projection and builds the SwiftPM package.
cmake --build out/context-for-claude-windows --config Release `
  --target build_swift_host

For ARM64, configure with -A ARM64. The projection command must run on Windows: this macOS development host cannot compile swiftwinrt.exe or exercise WinRT activation/UI runtime behavior.

Validate on macOS

macOS can validate the portable C++ boundary:

cmake -S desktop/context-for-claude/core -B /tmp/context-core
cmake --build /tmp/context-core
ctest --test-dir /tmp/context-core --output-on-failure

The Windows CMake project intentionally stops immediately on non-Windows hosts and does not fetch or pretend to validate swift-winrt there. The Swift host's Package.swift and source files are visible on macOS but cannot be built here — swift build for the x86_64-unknown-windows-msvc / aarch64-unknown-windows-msvc triples requires a Windows Swift toolchain.

Structure

windows/
├── CMakeLists.txt        Windows C++ hosts, swift-winrt projection, and Swift host build
├── src/core_smoke.cpp    Session/recall C ABI smoke test
├── src/session_host.cpp  Session-boundary host test
├── src/pcm_host.cpp      PCM encode/decode/RMS/downmix host test
├── swift-host/           SwiftPM package: imports WinRT projection + links C++ core
│   ├── Package.swift
│   └── Sources/
│       ├── CContextCore/     C ABI module map wrapper (header → ../core/include)
│       └── ContextWindowsHost/  Swift main: calls core C ABI + WinRT Uri
└── README.md