Abstract A combination of searches for top squark pair production using proton–proton collision data at a center-of-mass energy of 13 $$\,\text {Te}\text {V}$$ Te at the CERN LHC, corresponding to an integrated luminosity of 137 $$\,\text {fb}^{-1}$$ fb - 1 collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on the model, the combined result excludes a top squark mass up to 1325 $$\,\text {Ge}\text {V}$$ Ge for a massless neutralino, and a neutralino mass up to 700 $$\,\text {Ge}\text {V}$$ Ge for a top squark mass of 1150 $$\,\text {Ge}\text {V}$$ Ge . Top squarks with masses from 145 to 295 $$\,\text {Ge}\text {V}$$ Ge , for neutralino masses from 0 to 100 $$\,\text {Ge}\text {V}$$ Ge , with a mass difference between the top squark and the neutralino in a window of 30 $$\,\text {Ge}\text {V}$$ Ge around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 $$\,\text {Ge}\text {V}$$ Ge .