Diagnostic maps. Left: NE2025 Galactic DM (DM_MW) on the Northern Sky (N_side = 16), showing values of 50–250 pc cm⁻³ with the highest contributions near the Galactic plane. Middle: counts of all 2812 selected FRBs in N_side = 4 HEALPix pixels. The distribution is roughly uniform in R.A., with a concentration toward the North Celestial Pole (NCP) reflecting CHIME’s higher exposure at more northern declinations as a transit telescope. Right: jackknife range (max.−min. of DM contrast over 100 realizations each dropping 10% of FRBs). Typical ranges of ≲80 pc cm⁻³ around Wall 1 confirm that this excess is robust to the removal of individual events, although a somewhat increased range in the region of Wall 2 points to a lower significance of this feature.