  Using cosmic-ray boron to carbon ratio (B/C) data recently released by the
AMS-02 experiment, we find tantalizing indications ({\it decisive evidence}, in
Bayesian terms) in favor of a diffusive origin for the broken power-law spectra
found in protons ($p$) and helium nuclei (He). The result is robust with
respect to currently estimated uncertainties in the cross sections, and in the
presence of a small component of primary boron, expected because of spallation
at the acceleration site. Reduced errors at high energy as well as further
cosmic ray nuclei data (as absolute spectra of C, N, O, Li, Be) may
definitively confirm this scenario.
