Online accelerator modeling with two controls systems at FACET-II

FACET-II is a unique experimental facility housed in 1 km of the original Stanford Linear Accelerator tunnel. Multiple generations of hardware are still in use, as are two generations of software controls. A majority of subsystems (RF, magnets, timing, etc.) have their controls split across both ecosystems. Three software layers, including a newly-developed online modeling infrastructure, bridge this gap to form a unified high-level abstraction of the accelerator used for data analysis and as a foundation to develop control-room physics applications. We discuss the implementation of this infrastructure and some downstream programs.