  We explore the sensitivity of future hadron colliders to constrain the
fermionic Higgs portal, with a focus on scenarios where the new fermions cannot
be directly observed in exotic Higgs decays. This portal emerges in various
models including twin-Higgs scenarios and dark matter models, posing
significant challenges for collider tests. Working in an effective field theory
(EFT), we determine the reach of the high-luminosity option of the Large Hadron
Collider (HL-LHC), the high-energy upgrade of the LHC (HE-LHC) and a proposed
Future Circular Collider (FCC) in probing the fermionic Higgs portal through
off-shell and double-Higgs production. Notably, we find that quantum-enhanced
indirect probes offer a better sensitivity than other direct Higgs
measurements. We argue that this finding is valid in a wide class of
ultraviolet realisations of the EFT. Our study presents a roadmap of a
multifaceted search strategy for exploring the fermionic Higgs portal at
forthcoming hadron machines.
