Question

Problem

I am working on a project with C++ extensions that are built with scikit-build-core. To have proper editable installations, they recommend to use --no-build-isolation.

I have seen in the uv docs that this flag is properly supported for dependencies of your project, but nothing was mentioned on the project itself.

When trying to build it, it actually fails to build because uv doesn't pre-install the build dependencies.
I have put together a MRE in the following repo.

Current workaround

Currently, the you have to preinstall the build dependencies yourself. You can create a dependency group build to simplify the procedure, and even add it to the default groups to avoid uv sync removing it. But either way, you have to duplicate the list between the [dependency-groups] table and [build-system] table since you cannot include a dependency group in the build-system.requires.

Please propose better workarounds if you have some.

Question

Is this expected behavior? Is there some limitation that I am not aware of? I would find it reasonable to expect uv sync/uv run to preinstall the build dependencies by themselves.

Thank you a lot for your help

Platform

macOS 15.5 arm64

Version

uv 0.8.0 (0b23572 2025-07-17)