Decadal evolution of a repeating fast radio burst source

The origin of fast radio bursts (FRBs), the brightest cosmic radio explosions, is still unknown ^1–3 . Bearing critical clues to FRBs’ origin, the long-term evolution of FRBs has yet to be con- firmed, since the field is still young and most FRBs were seen only once. Here we report clear evidence of decadal evolution of FRB 20121102A, the first precisely localized repeater. In conjunction with archival data, our FAST and GBT monitoring campaign since 2020 reveals a significant ∼7% decline of local dispersion measure (DM). The rotation measure (RM) of 30,755±16 rad m ⁻² detected in the last epoch represents a 70% decrease compared to that from December 20165 . The σ _RM parameter, which describes the complexity of the magneto-ionic environment surrounding the source, was shown to have decreased by 13%. These general trends reveal an evolving FRB environment, which could originate from an early-phase su- pernova associated with an enhanced pair wind from the FRB central engine.