  A fundamental question in galaxy and black-hole evolution remains how
galaxies and their supermassive black holes have evolved together over cosmic
time. Specifically, it is still unclear how the position of X-ray active
galactic nucleus (AGN) host galaxies with respect to the star-forming main
sequence (MS) may change with the X-ray luminosity ($L_\mathrm{X}$) of the AGN
or the stellar mass ($M_\star$) of the host galaxy. We use data from XMM-SERVS
to probe this issue. XMM-SERVS is covered by the largest medium-depth X-ray
survey (with superb supporting multiwavelength data) and thus contains the
largest sample to date for study. To ensure consistency, we locally derive the
MS from a large reference galaxy sample. In our analysis, we demonstrate that
the turnover of the galaxy MS does not allow reliable conclusions to be drawn
for high-mass AGNs, and we establish a robust safe regime where the results do
not depend upon the choice of MS definition. Under this framework, our results
indicate that less-massive AGN host-galaxies ($\log M_\star\sim9.5-10.5$
$M_\odot$) generally possess enhanced SFRs compared to their normal-galaxy
counterparts while the more-massive AGN host galaxies ($\log
M_\star\sim10.5-11.5$ $M_\odot$) lie on or below the star-forming MS. Further,
we propose an empirical model for how the placement of an AGN with respect to
the MS (SFR$_{norm}$) evolves as a function of both $M_\star$ and
$L_\mathrm{X}$.
