  Context: Internal chemical mixing in intermediate- and high-mass stars
represents an immense uncertainty in stellar evolution models.In addition to
extending the main-sequence lifetime, chemical mixing also appreciably
increases the mass of the stellar core. Several studies have made attempts to
calibrate the efficiency of different convective boundary mixing mechanisms,
with sometimes seemingly conflicting results. Aims: We aim to demonstrate that
stellar models regularly under-predict the masses of convective stellar cores.
Methods: We gather convective core mass and fractional core hydrogen content
inferences from numerous independent binary and asteroseismic studies, and
compare them to stellar evolution models computed with the MESA stellar
evolution code. Results: We demonstrate that core mass inferences from the
literature are ubiquitously more massive than predicted by stellar evolution
models without or with little convective boundary mixing. Conclusions:
Independent of the form of internal mixing, stellar models require an efficient
mixing mechanism that produces more massive cores throughout the main sequence
to reproduce high-precision observations. This has implications for the
post-main sequence evolution of all stars which have a well developed
convective core on the main sequence.
