 The study shows that cilia-carpets exhibit self-organized metacrynal synchronization in the form of traveling waves, which enhances fluid transport. A multiscale model calibrated by an experimental cilia-beat pattern predicts multistability of wave modes, with a single mode having predominant basin of attraction. Relaxation times diverge with system size, ruling out global order in infinite systems. In finite systems, the study characterizes a synchronization transition as function of quenched frequency disorder using generalized Kuramoto order parameters. The framework termed Lagrangian mechanics of active systems allows to predict the direction and stability of metacrynal synchronization for given beat patterns. This article was authored by Anton Solove and Benjamin M. Friedrich.