2026ApJ..1000L..53P

We present the discovery and subsequent 3.2 yr monitoring campaign of the repeating fast radio burst (FRB) FRB 20220529A with CHIME/FRB. We observe a gradual decline in dispersion measure (DM) of -0.881 ± 0.001 pc cm^–3 yr^–1 (-1.235 ± 0.001 pc cm^–3 yr^–1 in the rest frame), implying a ≥3.5% ± 0.2% decrease in the total electron column in the source environment, and we see scattering timescale variations over weeks to years. We observe a short-lived excursion in which the DM rises by ∼1 pc cm^–3, immediately preceding an increase in transient Faraday rotation measure (RM) of ∼2000 rad m^–2 previously reported for this source, before returning to its gradual decline in DM. During this DM/RM excursion, we identify a local line-of-sight magnetic field of 3.4 ± 0.2 mG around FRB 20220529A, corresponding to one of the most strongly magnetized FRB environments. We measure a decrease in the linear polarization fraction of FRB 20220529A bursts with decreasing frequency that we attribute to depolarization from multipath propagation in the source environment. We also place a 5σ upper limit on the spectral luminosity of an associated persistent radio source of ≤5 × 10²⁸ erg s^–1 Hz^–1 at 1.5 GHz. These observations are consistent with FRB 20220529A originating from a young (approximately years to centuries old) expanding supernova remnant, with short-lived DM and RM variability arising from interactions with the supernova remnant or with a binary companion.