We refine the computation of the $\bar d-\bar u$ flavor asymmetry in the proton sea with
a complementary effort to reveal the dynamics
of pion exchange in high-energy processes. In particular,
we discuss the efficacy of pion exchange models to simultaneously
describe leading neutron electroproduction at HERA along with the
$\bar{d}-\bar{u}$ flavor asymmetry in the proton.
A detailed $\chi^2$ analysis of the ZEUS and H1 cross sections,
when combined with constraints on the pion flux from Drell-Yan
data, allows regions of applicability of one-pion exchange to be
delineated.
The analysis disfavors several models of the pion flux used in the
literature, and yields an improved extraction of the pion structure
function and its uncertainties at parton momentum fractions in the
pion of $4 \times 10^{-4} \lesssim x_\pi \lesssim 0.05$ at a scale
of $Q^2=10$~GeV$^2$.
Based on the fit results, we also address a possible estimate for leading proton
structure functions in upcoming tagged deep-inelastic scattering
experiments at Jefferson Lab on the deuteron with forward protons.