Impact of closed-loop F&F correction on the tip-tilt stability of the MITHIC bench. Main panel: measured radial offsets from the mean PSF centroid location as a function of iteration number, for the headline MITHIC F&F convergence test of Fig. 5 (blue) and a set of reference images containing only natural MITHIC bench image jitter (red). F&F convergence is taken to be achieved after five iterations. Inset panels: the central 0.3 λ/D pixels of the mean reference image (left) and the F&F-corrected image (right) respectively, each over-plotted with the centroid data used to compute jitter estimates. Dashed cross-hairs show the mean PSF centroid for each dataset, showing that F&F applies a systematic sub-pixel offset to align the PSF with its internal reference zero-point.