  Early data from the James Webb Space Telescope (JWST) has uncovered the
existence of a surprisingly abundant population of very massive galaxies at
extremely high redshift, which are hard to accommodate within the standard
$\Lambda$CDM cosmology. We explore whether the JWST observations may be
pointing towards more complex dynamics in the dark energy (DE) sector.
Motivated by the ubiquity of anti-de Sitter vacua in string theory, we consider
a string-inspired scenario where the DE sector consists of a negative
cosmological constant (nCC) and a evolving component with positive energy
density on top, whose equation of state is allowed to cross the phantom divide.
We show that such a scenario can drastically alter the growth of structure
compared to $\Lambda$CDM, and accommodate the otherwise puzzling JWST
observations if the dynamical component evolves from the quintessence-like
regime in the past to the phantom regime today: in particular, we demonstrate
that the presence of a nCC (which requires a higher density for the evolving
component) plays a crucial role in enhancing the predicted cumulative comoving
stellar mass density. Our work reinforces the enormous potential held by
observations of the abundance of high-$z$ galaxies in probing cosmological
models and new fundamental physics, including string-inspired ingredients.
