  Following the 2015 Planck release, we briefly comment on the status and some
ongoing opportunities in the interface between inflationary cosmology, string
theory, and CMB data. The constraints in the $r$-$n_s$ plane introduce a new
parameter into inflationary cosmology relative to the simplest quadratic
inflation model, in a direction which fits well with couplings to heavy fields
as occurs in string theory. The precision of the data permits further searches
for and constraints on additional model-dependent features, such as oscillatory
$N$-spectra, a program requiring specific theoretically motivated shapes. Since
the perturbations can easily be affected by additional sectors and couplings,
null results can usefully bound such contributions. We also review the broader
lessons string theory has contributed to our understanding of primordial
inflation, and close with some approaches to a more complete framework.
Published in a special volume of Comptes Rendus on Inflation: Theoretical and
Observational Status.
