  We present an improved calculation of the light CP-even Higgs boson pole mass
in the MSSM based on the FlexibleEFTHiggs hybrid method. The calculation resums
large logarithms to all orders and includes power-suppressed terms at fixed
order. It uses state-of-the-art 2- and 3-loop matching of the quartic Higgs
coupling and renormalization group running up to 4-loop, resulting in a
resummation of large logarithmic corrections up to N$^3$LL level. A
conceptually novel ingredient is the expansion of the matching conditions in
terms of high-scale MSSM parameters instead of SM parameters. In this way
leading terms in the stop-mixing parameter are effectively resummed, leading to
an improved numerical convergence of the perturbative expansion. Furthermore,
the avoidance of double counting of loop corrections is more transparent than
in other approaches and more independent of the high-scale model. We present
numerical results and a detailed discussion of theoretical uncertainties for
standard benchmark scenarios.
