Fast radio bursts (FRBs) are millisecond-duration, extremely bright radio flashes originating at cosmological distances, with a mix of apparently one-off events and repeaters that show different spectral, temporal, and polarization properties (Petroff et al. 2019; Cordes & Chatterjee 2019). In ΛCDM, explaining this diversity within standard stellar evolution and compact-object channels while also using FRBs as clean cosmological probes is challenging, because magnetars, mergers, and other proposed engines must be finely tuned to match rates, host environments, repetition statistics, and energetics without overproducing or underproducing specific subclasses (Zhang 2020; Luo et al. 2024).