Parameter space of orbital separations and companion masses that would produce either a significant Gaia proper motion anomaly or a higher-than-observed RUWE value in LkCa 15 and WISPIT 2, smoothed with a kernel density estimate (contours indicate the 20, 50, and 80% levels of the normalised area). These regions can be discarded as hosting a companion dominating the astrometry (Sect. 3.2, Eqs. (6), (7)). For WISPIT 2, the confirmed (at ∼57 au, van Capelleveen et al. 2025) and proposed (at ∼15 au, Close et al. 2025) planetary mass companions are indicated. Similar plots for all other 65 systems with non-detections are shown in Fig. A.3.