Phase convention (G6)

Every graph is exported as $G={\kappa }^2{N}_{ϵ}\hat{G}$ with $N_{ϵ}=i{S}_{ϵ}/16{\pi }^2$. For D01 and D03, $\hat{G}=-i\mathrm{pref}/{\kappa }^2\int$ with real export prefactors (${\kappa }^2/2$, $-{\kappa }^2$), so $A(d)$ carries an overall $i$. D13's exported prefactor is $i{\kappa }^2$, so its $A(d)$ is real. Because $sh=i(\dots )$, $X_{hh}$ is real like the D13 slot. The D01/D03 relative phase is tested by H3 (mutation M1 breaks it). The D13-versus-hh relative phase is not tested by a nonzero identity, since both slot contributions vanish. No physical overall phase is asserted.