The prefix is added as of scipy-openblas 0.3.24.95.0. Because the magic happens in the pkg-config Cflags, which are part of the wheel, older versoin can still be used and will work. They will not have the prefix, so newer versions should be prefered in order to avoid symbol confusion when more than one CBLAS library is linked in (like when mixing a NumPy built with the scipy-openblas wheels together with a SciPy that is built using a different CBLAS library).

LGTM, and I doubt there is a lot of complexity I am missing, thanks Matti.

If/when we would release wheels with this, they would need a version pin in principle to ensure that the user cannot have an older one already?
Although, if that is the case, I wonder if just janking old versions might also make sense.

Removing backport candidate, NumPy 1.26 doesn't include the scipy-openblas stuff.

If/when we would release wheels with this ...

The wheels will keep the old linking (i.e. not depending on the scipy-openblas wheels at runtime, only using them at build time and then shipping + RPATHing the shared objects) for the foreseeable future, since there are problems to express the metadata needed.