Starting June 8, GitHub Actions runners behind the windows-latest and windows-2025 labels will begin rolling over to Windows Server 2025 with Visual Studio 2026 — the cutover completes by June 15. Any workflow pinning assumptions about VS build toolchain version, MSVC flags, or preinstalled SDK paths should be tested now against the VS 2026 image before the rollover lands. The macOS side of this migration runs on a separate track: macos-latest starts shifting to macOS 26 on June 15, with that transition finishing by July 15. If you have matrix builds hitting both OS labels, you are looking at back-to-back image changes across the next six weeks — worth a single smoke-run in a non-default branch rather than discovering breakage in a release pipeline.