Windows: uv sync fails building cffi (MSVC required, no prebuilt wheel used)

[Liberaether]

Environment:

• OS: Windows 11 (PowerShell)
• Python: 3.14.x
• Package manager: uv

Problem:
Running uv sync on Windows fails when building cffi==1.17.1.

From the dependency chain:

• toolbox depends on cryptography (v45.0.4)
• cryptography depends on cffi
• uv does not pick up a prebuilt Windows wheel for cffi
• instead, it falls back to building cffi from source

During the build step, the process fails with the following error:

Microsoft Visual C++ 14.0 or greater is required

The failure happens inside setuptools.build_meta.build_wheel,
specifically during MSVC environment detection in distutils.

Steps to reproduce:

1. On a Windows machine without Microsoft C++ Build Tools installed
2. Run:

   uv sync

3. The build fails while compiling cffi

Expected behavior:

• On Windows, a precompiled wheel for cffi should be used if available
• Or the documentation should clearly state that MSVC Build Tools are required on Windows

Suggestions:

• Ensure Windows wheels for cffi are properly resolved when using uv
• Or document the Windows build requirements explicitly in the README / install guide

This issue is easy to hit on fresh Windows environments or CI machines.
Sharing this for awareness and possible improvement. Thanks!

[alex]

It's a bit hard to make sense of this:

cffi does publish wheels: https://pypi.org/project/cffi/#files. If they're not being installed, that's an issue with your environment or installer, there's nothing that cryptography can do to address this.

[reaperhulk]

cffi didn’t publish a 3.14 wheel for 1.17.1. The solution is to update the dep to 2.0. This isn’t a cryptography issue though, we don’t pin cffi.

[github-actions]

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