  Understanding the fate of planetary systems through white dwarfs which
accrete debris crucially relies on tracing the orbital and physical properties
of exo-asteroids during the giant branch phase of stellar evolution. Giant
branch luminosities exceed the Sun's by over three orders of magnitude, leading
to significantly enhanced Yarkovsky and YORP effects on minor planets. Here, we
place bounds on Yarkovsky-induced differential migration between asteroids and
planets during giant branch mass loss by modelling one exo-Neptune with inner
and outer exo-Kuiper belts. In our bounding models, the asteroids move too
quickly past the planet to be diverted from their eventual fate, which can
range from: (i) populating the outer regions of systems out to 10^4-10^5 au,
(ii) being engulfed within the host star, or (iii) experiencing
Yarkovsky-induced orbital inclination flipping without any Yarkovsky-induced
semimajor axis drift. In these violent limiting cases, temporary resonant
trapping of asteroids with radii of under about 10 km by the planet is
insignificant, and capture within the planet's Hill sphere requires fine-tuned
dissipation. The wide variety of outcomes presented here demonstrates the need
to employ sophisticated structure and radiative exo-asteroid models in future
studies. Determining where metal-polluting asteroids reside around a white
dwarf depends on understanding extreme Yarkovsky physics.
