Synthetic planetary populations resulting from the Monte Carlo runs of the GroMiT code, plotted in the final mass–final semimajor axis space. The cross indicates the median mass and semimajor axis of TOI-837 b, while the box shows the associated 3σ range of the planetary mass and semimajor axis. Left: results for both mm-sized (red) and cm-sized (blue) pebbles. Right: same as in the left panel, but including a colour scale to indicate the initial semimajor axes of the planetary seeds.