TEST1: Comparison of summary statistics of the initial density contrast field for the mock reference (dashed red line) and 500 independent reconstructions (solid blue line). Columns from left to right: (1) Monopole power spectrum; (2) quadrupole; (3) reduced bispectrum as a function of triangle opening angle, θ; and (4) cross-correlation coefficient C(k) between the reference and reconstruction (solid blue line) and the propagator (dashed red line), defined as the cross-correlation between the mock tracer density contrast and the initial density reference. In columns (1)–(3), the lower sub-panels display the ratios with respect to the reference. Shaded bands denote the 1σ intervals from the posterior samples. Vertical dashed lines indicate the isotropic Nyquist frequency, $k_{\mathrm{nyq}}/\sqrt{3}$.