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When building with VS2026 on Windows, use PlatformToolSet v145 by default #144679
Description
Activity
Using
v145also changes the appearance in the VS2026 solution explorer from
to
- added a commit that references this issue
on Feb 19, 2026 - added a commit that references this issue
on Feb 19, 2026 - added a commit that references this issue
on Feb 19, 2026 It can currently build without modifying any files, but packaging into an MSI bundle still fails. When running
./Tools/msi/buildrelease.bat, I always get:
MSB8020: The build tools for v145 (Platform Toolset = 'v145') cannot be found.Detailed outputs:
$ ./Tools/msi/buildrelease.bat -x64 --skip-nuget --skip-build Using py -3.14 (found 3.14 with py.exe) Fetching external libraries... Fetching external tools... binutils already exists, skipping. gpg already exists, skipping. htmlhelp already exists, skipping. nuget already exists, skipping. redist-1 already exists, skipping. wix-314 already exists, skipping. Finished. Using "C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Current\Bin\amd64\MSBuild.exe" (found in the PATH) MSBuild version 18.3.0-release-26070-10+3972042b7 for .NET Framework Build started 2026/2/21 8:31:01. Project "E:\Sources\Python\Tools\msi\launcher\launcher.wixproj" on node 1 (default targets). Project "E:\Sources\Python\Tools\msi\launcher\launcher.wixproj" (1) is building "E:\Sources\Python\PCbuild\pyshellext.vcxproj" (2) on node 1 (Build target(s)). C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VC\v180\Microsoft.CppBuild.targets(473,5): error MSB8020: The build tools for v145 (Platform Toolset = 'v145') cannot be found. T o build using the v145 build tools, please install v145 build tools. Alternatively, you may upgrade to the current Visual Studio tools by selecting the Project menu or right-click the solution, and th en selecting "Retarget solution". [E:\Sources\Python\PCbuild\pyshellext.vcxproj] Done Building Project "E:\Sources\Python\PCbuild\pyshellext.vcxproj" (Build target(s)) -- FAILED. Done Building Project "E:\Sources\Python\Tools\msi\launcher\launcher.wixproj" (default targets) -- FAILED. Build FAILED. "E:\Sources\Python\Tools\msi\launcher\launcher.wixproj" (default target) (1) -> "E:\Sources\Python\PCbuild\pyshellext.vcxproj" (Build target) (2) -> (PrepareForBuild target) -> C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VC\v180\Microsoft.CppBuild.targets(473,5): error MSB8020: The build tools for v145 (Platform Toolset = 'v145') cannot be found. To build using the v145 build tools, please install v145 build tools. Alternatively, you may upgrade to the current Visual Studio tools by selecting the Project menu or right-click the solution, and then selecting "Retarget solution". [E:\Sources\Python\PCbuild\pyshellext.vcxproj] 0 Warning(s) 1 Error(s) Time Elapsed 00:00:00.18
$ ./Tools/msi/buildrelease.bat -x64 --skip-nuget --skip-build
Sorry, I cannot reproduce. This builds
launcher.wixproj/pyshellext.vcxprojfor me in a fresh environment and creates a workinglauncher.msi. But then soon later of course fails due to missing files because of--skip-build.Hence, I also did a "full" build
$ ./Tools/msi/buildrelease.batand got a working
launcher.msi, installerpython-3.15.0a6-amd64.exeandpython-3.15.0a6-embed-amd64.zip.It can currently build without modifying any files
So it seems
v145is found in this case ...but packaging into an MSI bundle still fails
... but here it is not found in your case. This is weird, so I can only speculate: maybe you do not have
v145for x86 and arm installed? For the launcher, shellext is built in those configurations, too ...Thanks for the reply. I can confirm your findings. Running
./Tools/msi/buildrelease.bat -x64 --skip-nugetin a clean VM environment completes without any issues.For context, I had previously run
./PCbuild/build.batto generate the binaries and added--skip-buildtobuildrelease.batexpecting it to reuse the existing build outputs. It turns out that doing so somehow leads to thev145not found error.Since it works seamlessly without the flag in a clean environment, the required toolchains are definitely present. Appreciate your time checking this!
Reacted by Chris Eibl@DEVwXZ4Njdmo4hm Just as a heads-up, we'll be deleting the MSI build in its entirety after 3.15 gets its own branch - it won't be part of 3.16. So if you're relying on it, you'll want to be planning to fork that part yourself at some point (or possibly just create a simpler one). See PEP 773 for more info.
Triage: @chris-eibl, is this complete?
Yes - the only reason I've kept it open was to remind me to switch from the preview
windows-2025-vs2026towindows-2025once the latter officially supports VS2026 (which should happen soon). Best done after the 3.15 beta1 release I think.But this most probably deserves its own issue, anyway ...
But this most probably deserves its own issue, anyway ...
Done #150605, so closing here.
- added a commit that references this issue
on Sep 25, 2026
As discussed offline with @zooba and @Fidget-Spinner as a preparational step to be able to use tailcalling (#139922) for the official Windows binaries beginning with 3.15.
Linked PRs
windows-2025-vs2026in GitHub Actions #145005