  Extending the Standard Model with a new complex singlet scalar, right-handed
neutrinos and a vector-like quark allows to simultaneously tackle several
problems in particle physics and cosmology within a constrained framework that
can be falsified by future probes of the cosmic microwave background, as well
as by upcoming axion experiments. This Standard Model - Axion - Seesaw - H
portal inflation theory (SMASH) provides predictive inflation and $H$ boson
stabilization, and can explain baryogenesis, light neutrino masses, dark matter
and the strong CP problem. The model contains a unique new mass scale which
coincides with the axion decay constant, and also sets the scale for
perturbative lepton-number violation processes. Testable predictions include a
minimum value of the tensor-to-scalar ratio of $r\gtrsim 0.004$, a running of
the spectral index $\alpha\gtrsim-8\times10^{-4}$, a change $\delta N_{\rm
eff}\sim 0.03$ in the number of effective relativistic neutrinos, and an axion
mass in the range $50\mu eV\leq m_A \leq 200 \mu eV$.
