I present a fully analytic account of lepton $g$–factors within the Relator framework based on the single postulate $R\,\omega=c$. Internal phase evolution in $\mathbb{C}$-space acquires a self–Coulomb (and, in principle, gravitational) slowdown $\delta_C$; taking the measured Larmor rate as the clock and assigning this slowdown differentially to the orbital sector yields the closed mapping $g=2/\sqrt{1-\delta_C}$. A mode selection fixes the baseline $\delta_C$ in closed form \emph{without} perturbative QED, virtual quanta, or external renormalization. To capture the inter-lepton splitting with one universal input, I posit a mass-linear correction $\delta_{\rm tot}(m)=\delta_0+\Gamma m$, calibrated on $(e,\mu)$, which then provides a parameter-free prediction for $\tau$. All results follow directly from $R\,\omega=c$ and are testable in Penning-trap and storage-ring settings.