{57}$Zn $\beta$-delayed proton emission establishes the $^{56}$Ni $rp$-process waiting point bypass

•In our letter, we address the dominant uncertainty regarding the extent of the rp-process flow bypass around Ni 56 waiting point for astrophysical conditions relevant to Type-1 X-ray bursts.•We removed the final significant uncertainty, the beta-delayed proton branching ratio for Zn 57 , definitively determining that there is a Ni 56 bypass.•In addition, we also identified the second case of the exotic β − γ − p decay mode in the fp-shell. We measured the Zn 57 β-delayed proton (βp) and γ emission at the National Superconducting Cyclotron Laboratory. We find a Zn 57 half-life of 43.6±0.2 ms, βp branching ratio of ( 84.7±1.4 ) % , and identify four transitions corresponding to the exotic β-γ-p decay mode, the second such identification in the fp-shell. The p/γ ratio was used to correct for isospin mixing while determining the Zn 57 mass via the isobaric multiplet mass equation. Previously, it was uncertain as to whether the rp-process flow could bypass the textbook waiting point Ni 56 for astrophysical conditions relevant to Type-I X-ray bursts. Our results definitively establish the existence of the Ni 56 bypass, with 14-17% of the rp-process flow taking this route.