  Axion-mediated forces are enhanced by the presence of CP-violating axion
couplings, which are however tightly constrained by electric dipole moment
(EDM) searches. We discuss the underlying hypotheses behind different sources
of CP violation at high energies and the interplay between axion-mediated force
experiments and EDM observables. Specifically, we identify various mechanisms,
based on new sources of CP violation or Peccei-Quinn symmetry breaking, that
can significantly relax EDM constraints, leading to a substantial redefinition
of the QCD axion window for axion-mediated forces. By considerably enlarging
the QCD axion parameter space, our results provide a well-motivated target for
experiments probing scalar axion couplings to matter fields. These include
fifth-force tests of gravity, as well as searches for spin-dependent forces via
precision magnetometry, proton storage rings and ultracold molecules.
