  Thin-film nanostructures with embedded M\"ossbauer nuclei have been
successfully used for x-ray quantum optical applications with hard x-rays
coupling in grazing incidence. Here we address theoretically a new geometry, in
which hard x-rays are coupled in forward incidence (front coupling), setting
the stage for waveguide QED with nuclear x-ray resonances. We present in a
self-contained manner a general model based on the Green's function formalism
of the field-nucleus interaction in one dimensional waveguides, and show that
it combines aspects of both nuclear forward scattering, visible as dynamical
beating in the spatio-temporal response, and the resonance structure from
grazing incidence, visible in the spectrum of guided modes. The interference of
multiple modes is shown to play an important role, resulting in beats with
wavelengths on the order of tens of microns, on the scale of practical
photolithography. This allows for the design of special sample geometries to
explore the resonant response or micro-striped waveguides, opening a new
toolbox of geometrical design for hard X-ray quantum optics.
