Precision calculations for groomed event shapes at HERA

The possibility to reanalyse data taken by the HERA experiments offers the chance to study modern QCD jet and event-shape observables in deep-inelastic scattering production. In this contribution we present resummed and matched predictions for the groomed invariant-mass event shape in neutral-current DIS including the effect of grooming the hadronic final state using the soft-drop technique. Non-perturbative corrections from hadronisation are taken into account through parton- to-hadron level transfer matrices extracted from dedicated Monte Carlo simulations with SHERPA, including uncertainties extracted from replica tunes to data from the HERA experiments.