What's Changed

• base_identity.h: added missing constexpr by Mathias Berchtold (@matbech) in #1589
• Stop exporting winrt::impl::get_marshaler to workaround MSVC modules bug by Ryan Shepherd (@DefaultRyan) in #1592
• Migrate GitHub CI off VS 2022, add C++20 module test, dynamic v143/v145 toolset by Ryan Shepherd (@DefaultRyan) with @Copilot in #1601
• Massive speedup to file_equal and file_to_string by Ryan Shepherd (@DefaultRyan) in #1584
• Improve and ship module docs. Add missing properties to VS project properties page by Ryan Shepherd (@DefaultRyan) in #1586
• Bump actions/checkout from 6 to 7 by Dependabot (@dependabot)[bot] in #1600
• Fix C4819 warning: replace non-ASCII em dash in base_macros.h comment by Ryan Shepherd (@DefaultRyan) with @Copilot in #1606

New Contributors

• Mathias Berchtold (@matbech) made their first contribution in #1589

Full Changelog: 3.0.260520.1...3.0.260715.1

Major additions and breaking changes

In addition to the usual bugfixes and enhancements, this first 3.0 release contains two major updates: support for C++20 modules, and support for deprecated pre-standard coroutines has been removed.

Removing pre-standard coroutines

C++/WinRT has removed support for the pre-standard coroutines via the /await compiler option and the <experimental/coroutine> header. This aligns with the new behavior in the MSVC Build Tools 14.50 (shipping in Visual Studio 2026) that officially deprecated /await, and will soon deprecate the experimental headers. Standard coroutines are available by default starting in C++20, or if you are still on C++17, use /await:strict.

If your existing projects are using the Nupkg support out of the box and have not manually added /await, you probably won't have to change anything, as we've updated the default behavior in Microsoft.Windows.CppWinRT.targets to use /await:strict when building with C++17. If for some reason, you need to override this default behavior in the targets file, you can set CppWinRTEnableCpp17Coroutines to false to prevent it from auto-setting /await:strict.

Module support

Full module support has finally arrived to C++/WinRT! Replace

#include <winrt/Windows.Foundation.h>

with

import winrt.Windows.Foundation;

and rejoice!

This brings potential improvements in build speed, disk space, and memory usage, particularly for large projects using Xaml projections, and starts to isolate more of the internal C++/WinRT implementation details from the consumer side. Test-driving this work on a quick and dirty prototype fork of Windows Terminal yielded a 10-15% build speed improvement (22 minutes before, 19 minutes after), and a reduction in disk space from 30GB down to 18GB.

If you've ever used C++/WinRT with Windows.UI.Xaml.*, you've probably moved those headers into your precompiled header (PCH), but then saw your PCH consume well upwards of 1-2GB of disk space per vcxproj, per flavor. In the Terminal prototype, taking these headers out of the PCH and replacing them with a single cppwinrt module, built once and shared between projects, the PCHs shrunk by upwards of 80%, and the time to build each PCH went from ~40 seconds down to ~5 seconds. The single prebuilt cppwinrt modules carried all of the types for the entire Windows.* namespaces and WinUI, and still consumed only 700MB, and took ~80-90 seconds to build. Excluding unused namespaces from the module build can lower those numbers even further. The Terminal prototype didn't do this, and still enjoyed immediate wins on disk space, and the build time wins broke even after converting about 2-3 projects out of the ~15 or so that use C++/WinRT.

As part of this large effort, we no longer generate the old monolithic module interface file winrt.ixx, but instead generate a module interface .ixx file for each WinRT namespace. There is more documentation at nuget/modules/md to help get you started.

What's changed

• Enable NuGet Central Package Management by Ryan Shepherd (@DefaultRyan) in #1483
• Declare public LTO visibility for ABI type declarations by Brady Hahn (@ZeroMemes) in #1482
• All cppwinrt vcxproj should build with /W4 and /WX (warnings turned up, treated as error). Fix existing violations. by David Machaj (@dmachaj) in #1487
• fix indent in generated code by David Lechner (@dlech) in #1489
• Bump actions/checkout from 4 to 5 by Dependabot (@dependabot)[bot] in #1502
• Bump actions/download-artifact from 4 to 5 by Dependabot (@dependabot)[bot] in #1501
• Bump actions/stale from 9 to 10 by Dependabot (@dependabot)[bot] in #1507
• Fix CI build by using latest Windows SDK in C# project by Ryan Shepherd (@DefaultRyan) in #1516
• Remove throwing/originating errors in expected scenarios (Lookup/TryLookup and Cancel) by antmor in #1512
• Bump actions/download-artifact from 5 to 6 by Dependabot (@dependabot)[bot] in #1519
• Bump actions/upload-artifact from 4 to 5 by Dependabot (@dependabot)[bot] in #1518
• Bump actions/checkout from 5 to 6 by Dependabot (@dependabot)[bot] in #1523
• Bump actions/upload-artifact from 5 to 6 by Dependabot (@dependabot)[bot] in #1525
• Bump actions/download-artifact from 6 to 7 by Dependabot (@dependabot)[bot] in #1526
• Enable PreFast for build stage in OneBranch pipeline by Vineeth Thomas Alex (@vineeththomasalex) in #1533
• Update PreFast run stage in OneBranchBuild.yml to "Guardian" to avoid race condition with build. by Vineeth Thomas Alex (@vineeththomasalex) in #1534
• Remove Windows pool from build stage by Vineeth Thomas Alex (@vineeththomasalex) in #1535
• Only sign the VSIX contents instead of the entire temp directory by Ryan Shepherd (@DefaultRyan) in #1537
• Fix handling of NuGet package version in VSIX by Ryan Shepherd (@DefaultRyan) in #1536
• Fix accidentally deleted parameter by Ryan Shepherd (@DefaultRyan) in #1538
• Delete stale.yml by Stephan T. Lavavej (@StephanTLavavej) in #1543
• Bump actions/download-artifact from 7 to 8 by Dependabot (@dependabot)[bot] in #1541
• Bump actions/upload-artifact from 6 to 7 by Dependabot (@dependabot)[bot] in #1542
• Simplify the definition of the consume function by Yexuan Xiao (@YexuanXiao) in #1544
• Remove experimental coroutines support by Charles Milette (@sylveon) in #1521
• Add missing headers and std qualification, use std::numeric_limits in… by Yexuan Xiao (@YexuanXiao) in #1546
• Fix race condition in multi_threaded_observable_map test by Ryan Shepherd (@DefaultRyan) in #1550
• Fix integer fields causing impl promotion by Charles Milette (@sylveon) in #1551
• box_value constructor: Replace param::hstring with hstring by justanotheranonymoususer in #1530
• fix: normalize CRLF to LF in test/test/box_string.cpp by @Copilot in #1557
• Breaking coroutines means v3.0 by Ryan Shepherd (@DefaultRyan) in #1547
• Add inline for hstring_reference_flag by Yexuan Xiao (@YexuanXiao) in #1571
• CI: test against VS2022 (v143) and VS2026 (v145) in parallel by @Copilot in #1573
• Move operator<< to winrt::Windows::Foundation by Yexuan Xiao (@YexuanXiao) in #1576
• C++20 module support v2 by Ryan Shepherd (@DefaultRyan) in #1575

New Contributors

• Brady Hahn (@ZeroMemes) made their first contribution in #1482
• antmor made their first contribution in #1512
• Vineeth Thomas Alex (@vineeththomasalex) made their first contribution in #1533
• Stephan T. Lavavej (@StephanTLavavej) made their first contribution in #1543
• Yexuan Xiao (@YexuanXiao) made their first contribution in #1544
• justanotheranonymoususer made their first contribution in #1530
• @Copilot made their first contribution in #1557

Full Changelog: 2.0.250303.1...3.0.260520.1

What's Changed

• Use actions/cache@v4 by Josh Soref (@jsoref) in #1411
• Spelling by Josh Soref (@jsoref) in #1412
• Changed visibility of observable_map_base::call_changed to protected by Felix Patschkowski (@Patschkowski) in #1425
• Add missing <exception> to base_includes.h by Michael Maltsev (@m417z) in #1427
• Add NuGet config by Manodasan Wignarajah (@manodasanW) in #1433
• Update NuGetCommand to use nuget.config by Manodasan Wignarajah (@manodasanW) in #1434
• Clarify how InitializeComponent works in the template comment by L Thorn (@la-thorn) in #1435
• Silence clang-tidy "unused variable" warnings by Duncan Horn (@dunhor) in #1438
• Value-init fields of WinRT structs (fix warning C24695 in generated code) by Ryan Shepherd (@DefaultRyan) in #1443
• Bug: Projected winrt::consume_ methods will nullptr crash if the underlying QueryInterface call fails by David Machaj (@dmachaj) in #1442
• WINRT_SOURCE_LOCATION has ODR checks that prevent mixing cpp17 and cpp20 static libraries by David Machaj (@dmachaj) in #1444
• Latest vpack has an extra cppwinrt folder by Ryan Shepherd (@DefaultRyan) in #1447
• Reduce the code size of generated consume methods by skipping casts when the type is already a match by David Machaj (@dmachaj) in #1448
• try_as casts should not store COM error context; consume method cast checking should use return codes directly by David Machaj (@dmachaj) in #1450
• Try to fix the disabled/failing nuget test build step by David Machaj (@dmachaj) in #1451
• GitHub Actions workflow cannot build arm32 after updating Windows SDK by David Machaj (@dmachaj) in #1454
• The new variables in winrt::impl::consume_ methods can collide with parameters to that method by David Machaj (@dmachaj) in #1455
• Fix overloads coming from overridable interfaces by Charles Milette (@sylveon) in #1458
• Make consume methods more amenable to optimization by Ryan Shepherd (@DefaultRyan) in #1462
• Fix warnings in natvis project by Ryan Shepherd (@DefaultRyan) in #1463
• Fix reading past end of array. by David Lechner (@dlech) in #1468
• Fix setting of IntDir MSBuild property by Ryan Shepherd (@DefaultRyan) in #1471
• Allow visualization of properties on generic types by Ryan Shepherd (@DefaultRyan) in #1472
• Fix various build warnings by Ryan Shepherd (@DefaultRyan) in #1473
• Configure guardian, SDL, TSA, and CodeQL in Official Builds by Ryan Shepherd (@DefaultRyan) in #1474
• Clean up more warnings and Component Governance by Ryan Shepherd (@DefaultRyan) in #1475
• Stop manually downloading hardcoded version of llvm/clang. by Ryan Shepherd (@DefaultRyan) in #1478
• Enable prefast and warnings checker in SDL by Ryan Shepherd (@DefaultRyan) in #1477
• Merge compiler and msbuild vpacks by Ryan Shepherd (@DefaultRyan) in #1479
• Fix vpack clobbering and update to newer Windows container image by Ryan Shepherd (@DefaultRyan) in #1480

New Contributors

• Felix Patschkowski (@Patschkowski) made their first contribution in #1425
• Michael Maltsev (@m417z) made their first contribution in #1427
• L Thorn (@la-thorn) made their first contribution in #1435

Full Changelog: 2.0.240405.15...2.0.250303.1

Changes:

• d2a6677 Remove references to stale winmd files to fix incremental builds (#1404)
• e03bdc4 Use latest upload/download actions (#1410)
• 17d095a Fix build following dependabot updates (#1409)
• 2b8fe6e Revert "Bump actions/upload-artifact from 3 to 4 (#1407)"
• ea18769 Bump actions/download-artifact from 3 to 4 (#1408)
• 6f74952 Bump actions/upload-artifact from 3 to 4 (#1407)
• 523eda7 Bump actions/stale from 6 to 9 (#1405)
• dfad7ed Bump actions/checkout from 3 to 4 (#1406)
• f0ce6c6 Create dependabot.yml
• adc6ef9 TDBuild - updating localized resource files.

Changes:

• 25a14f8 Update build.yml for Azure Pipelines (#1384) [ #1338 ]
• cb67472 CppWinRTAddXamlReferences to not use outputs as inputs (#1381)
• 5ef408f User/dmachaj/slim source location (#1379)
• 2511bf7 Update pool (#1374)
• fc587f3 Allow delegates to be created with weak reference + lambda (#1372) [ #1371 ]
• 912aa47 Update GitHub action LLVM version to 17.0.5 (#1373)
• bf4459b Allow resume_agile to be stored in a variable (#1358)
• fac72c8 Add resume_agile to allow coroutine to resume in any apartment (#1356)
• 23c4ced Improve GCC compatibility (#1352)
• 691f6f8 Support for std::span for winrt::array_view and winrt::com_array (#1343)

Changes:

• 297454e Allow classic COM interfaces with get_self (#1314) [ #1312 ]
• d3bb275 Fix source location test failure resulting from newer compiler (#1326)
• ec54c40 Clarify contributing guide (#1324)
• c24bc39 Fix workflow trigger (#1321)
• ed6a1e3 Update open source docs (#1315)
• e2dc214 Update readme

This list of changes was auto generated.

Changes:

• 0e740b1 Update issue template to use cpp instead of rust (#1313)
• 780e095 Add UTF-8 path support (#1307)
• 858d503 Disable MSYS2 mingw32 CI due to running out of memory (#1305)

This list of changes was auto generated.

Changes:

• 4587264 Remove explicitly setting PreferredToolArchitecture, since VS 2022 handles this more comprehensively (#1304)
• 49b2cab Remove ARM OneBranch build workaround (#1303)
• 65581a3 Add capture support for unconventional result types (#1301)
• c3b7fcf Move official build pipelines to OneBranch (#1295)
• 6162c9d Fix flakey clock and line-number tests (#1294)
• a1b9593 Use safe DLL loading (avoid current directory) (#1293)
• 737adea Compliance and test cleanup (#1291)
• f3c7309 Expose configuring /nomidl. (#1290)
• 9e89b5c Create pipeline to sync mirror repo (#1286)
• 629f9e7 Update README.md

This list of changes was auto generated.

What's Changed

• Stack usage reduction in apartment switching, and lifetime fixes by Raymond Chen (@oldnewthing) in #1272
• Reduce stack consumption if unable to switch to apartment_context by Raymond Chen (@oldnewthing) in #1276
• Fix unreliable clock epoch tests by Raymond Chen (@oldnewthing) in #1277
• to_hstring for IStringable by @JaiganeshKumaran in #1271
• Add a clang-specific impl->projection conversion operator by Dustin L. Howett (@DHowett) in #1274

New Contributors

• Dustin L. Howett (@DHowett) made their first contribution in #1274

Full Changelog: 2.0.230207.1...2.0.230225.1

What's Changed

• Fix llvm-mingw tests with LLVM trunk by alvinhochun (@alvinhochun) in #1235
• cppwinrt: Support Linux cross-build with mingw-w64 by alvinhochun (@alvinhochun) in #1238
• CI: Refactor LLVM setup steps and use cache by alvinhochun (@alvinhochun) in #1242
• Add Linux native build by alvinhochun (@alvinhochun) in #1239
• Make compatible with GCC by alvinhochun (@alvinhochun) in #1245
• FIx build on macOS and add CI build by alvinhochun (@alvinhochun) in #1247
• Improve error reporting for clock test by Kenny Kerr (@kennykerr) in #1248
• Fix cancellation propagation by moving responsability to awaiter by Charles Milette (@sylveon) in #1246
• Try to fix random failure of the clock test by alvinhochun (@alvinhochun) in #1251
• Clarify object usage after move in make_delegate_with_shared_state by yuvaln-s1 in #1253
• mingw: Stop using .weak symbols aliases by alvinhochun (@alvinhochun) in #1250
• cmake: Allow using external winmd headers to bypass download by alvinhochun (@alvinhochun) in #1256
• Make headers partially usable with LLVM/libc++ 13 by alvinhochun (@alvinhochun) in #1257
• Cleaning up some warnings for Clang and GCC by alvinhochun (@alvinhochun) in #1255
• Add option for using custom license text by alvinhochun (@alvinhochun) in #1262
• Add a mechanism to suppress std::source_location by David Machaj (@dmachaj) in #1260
• tests: Fix and enable cpp20/custom_error for incoming LLVM 16 by alvinhochun (@alvinhochun) in #1265
• Move build pipeline into YAML by Ryan Shepherd (@DefaultRyan) in #1268
• Make the formatter for IStringable const by Charles Milette (@sylveon) in #1270
• Workaround for false positive code analysis warning by Kenny Kerr (@kennykerr) in #1269

New Contributors

• yuvaln-s1 made their first contribution in #1253

Full Changelog: 2.0.221121.5...2.0.230207.1