  Gamma-ray burst GRB221009A was of unprecedented brightness in gamma-rays and
X-rays, and through to the far ultraviolet, allowing for identification within
a host galaxy at redshift z=0.151 by multiple space and ground-based
optical/near-infrared telescopes and enabling a first association - via
cosmic-ray air-shower events - with a photon of 251 TeV. That is in direct
tension with a potentially observable phenomenon of quantum gravity (QG), where
spacetime "foaminess" accumulates in wavefronts propagating cosmological
distances, and at high-enough energy could render distant yet bright pointlike
objects invisible, by effectively spreading their photons out over the whole
sky. But this effect would not result in photon loss, so it remains distinct
from any absorption by extragalactic background light. A simple multiwavelength
average of foam-induced blurring is described, analogous to atmospheric seeing
from the ground. When scaled within the fields of view for the Fermi and Swift
instruments, it fits all z<5 GRB angular-resolution data of 10 MeV or any
lesser peak energy and can still be consistent with the highest-energy
localization of GRB221009A: a limiting bound of about 1 degree is in agreement
with a holographic QG-favored formulation.
