arXiv:2611.06466v1 Announce Type: cross Abstract: Phase locking in oscillator networks depends critically on the interaction strengths between coupled units. In many applications, however, these couplings are uncertain, state dependent, or time varying. We derive rigorous conditions for phase locking in Kuramoto-type networks when each coupling strength is known only within prescribed bounds. Building on a convex formulation of the nonlinear fixed-point equations, we obtain edge-wise error bounds for arbitrary feasible approximations that hold uniformly over all admissible couplings. These bounds yield sufficient conditions for the existence of phase-locked states with prescribed phase-difference limits. We illustrate the framework for AC power grids with uncertain voltage magnitudes and adaptive oscillator networks with state-dependent couplings. For the latter, the bounds can be further tightened by exploiting the state dependence of the couplings.