  Developing complex, reliable advanced accelerators requires a coordinated,
extensible, and comprehensive approach in modeling, from source to the end of
beam lifetime. We present highlights in Exascale Computing to scale accelerator
modeling software to the requirements set for contemporary science drivers. In
particular, we present the first laser-plasma modeling on an exaflop
supercomputer using the US DOE Exascale Computing Project WarpX. Leveraging
developments for Exascale, the new DOE SCIDAC-5 Consortium for Advanced
Modeling of Particle Accelerators (CAMPA) will advance numerical algorithms and
accelerate community modeling codes in a cohesive manner: from beam source,
over energy boost, transport, injection, storage, to application or
interaction. Such start-to-end modeling will enable the exploration of hybrid
accelerators, with conventional and advanced elements, as the next step for
advanced accelerator modeling. Following open community standards, we seed an
open ecosystem of codes that can be readily combined with each other and
machine learning frameworks. These will cover ultrafast to ultraprecise
modeling for future hybrid accelerator design, even enabling virtual test
stands and twins of accelerators that can be used in operations.
