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When building with VS2026 on Windows, use PlatformToolSet v145 by default #144679

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When building with VS2026 on Windows, use PlatformToolSet v145 by default#144679
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chris-eibl
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3.15bugs and security fixesOS-windowsbuildThe build process and cross-buildpendingThe issue will be closed if no feedback is providedtype-featureA feature request or enhancement

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  1. chris-eibl
    added
    OS-windows
    buildThe build process and cross-build
    3.15bugs and security fixes
    on Feb 10, 2026
  2. chris-eibl
    self-assigned this
    on Feb 10, 2026

  3. chris-eibl commented on Feb 10, 2026

    @chris-eibl
    chris-eibl
    on Feb 10, 2026
    MemberAuthor

    Using v145 also changes the appearance in the VS2026 solution explorer from

    Image

    to
    Image

  4. zooba
    added a commit that references this issue on Feb 19, 2026

    GH-144679: When building with VS 2026 on Windows, use PlatformToolset…

    c06f4f4
  5. Fidget-Spinner
    added a commit that references this issue on Feb 19, 2026

    GH-144679: MSVC tailcall CI no longer needs to specify PlatformToolset (

    0341b10
  6. zooba
    added a commit that references this issue on Feb 19, 2026

    GH-144679: Switch to windows-2025-vs2026 build image in GitHub Actions (

    6485c85

  7. DEVwXZ4Njdmo4hm commented on Feb 21, 2026

    @DEVwXZ4Njdmo4hm
    DEVwXZ4Njdmo4hm
    on Feb 21, 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

  8. chris-eibl commented on Feb 21, 2026

    @chris-eibl
    chris-eibl
    on Feb 21, 2026
    MemberAuthor

    $ ./Tools/msi/buildrelease.bat -x64 --skip-nuget --skip-build

    Sorry, I cannot reproduce. This builds launcher.wixproj / pyshellext.vcxproj for me in a fresh environment and creates a working launcher.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.bat

    and got a working launcher.msi, installer python-3.15.0a6-amd64.exe and python-3.15.0a6-embed-amd64.zip.

    It can currently build without modifying any files

    So it seems v145 is 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 v145 for x86 and arm installed? For the launcher, shellext is built in those configurations, too ...

  9. DEVwXZ4Njdmo4hm commented on Feb 22, 2026

    @DEVwXZ4Njdmo4hm
    DEVwXZ4Njdmo4hm
    on Feb 22, 2026

    Thanks for the reply. I can confirm your findings. Running ./Tools/msi/buildrelease.bat -x64 --skip-nuget in a clean VM environment completes without any issues.

    For context, I had previously run ./PCbuild/build.bat to generate the binaries and added --skip-build to buildrelease.bat expecting it to reuse the existing build outputs. It turns out that doing so somehow leads to the v145 not found error.

    Since it works seamlessly without the flag in a clean environment, the required toolchains are definitely present. Appreciate your time checking this!

  10. zooba commented on Feb 23, 2026

    @zooba
    zooba
    on Feb 23, 2026
    Member

    @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.

  11. brijkapadia
    added 3 commits that reference this issue on Feb 28, 2026

    pythonGH-144679: When building with VS 2026 on Windows, use PlatformT…

    8174d4e

    pythonGH-144679: MSVC tailcall CI no longer needs to specify Platform…

    60d6b7e

    pythonGH-144679: Switch to windows-2025-vs2026 build image in GitHub …

    e63f2ea
  12. ljfp
    added 3 commits that reference this issue on Apr 25, 2026

    pythonGH-144679: When building with VS 2026 on Windows, use PlatformT…

    568bd59

    pythonGH-144679: MSVC tailcall CI no longer needs to specify Platform…

    46269fb

    pythonGH-144679: Switch to windows-2025-vs2026 build image in GitHub …

    cc82e0c

  13. StanFromIreland commented on May 2, 2026

    @StanFromIreland
    StanFromIreland
    on May 2, 2026
    Member

    Triage: @chris-eibl, is this complete?

  14. StanFromIreland
    added
    type-featureA feature request or enhancement
    pendingThe issue will be closed if no feedback is provided
    on May 2, 2026

  15. chris-eibl commented on May 2, 2026

    @chris-eibl
    chris-eibl
    on May 2, 2026
    MemberAuthor

    Yes - the only reason I've kept it open was to remind me to switch from the preview windows-2025-vs2026 to windows-2025 once 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 ...

  16. chris-eibl commented on May 30, 2026

    @chris-eibl
    chris-eibl
    on May 30, 2026
    MemberAuthor

    But this most probably deserves its own issue, anyway ...

    Done #150605, so closing here.

  17. chris-eibl
    closed this as completedon May 30, 2026
  18. pablogsal
    added a commit that references this issue on Sep 25, 2026

    [3.14] GH-144679: When building with VS 2026 on Windows, use Platform…

    2649b37
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