The circumgalactic medium (CGM), through which gas flows into the galaxy from the cosmic web, and where energy and metals are deposited by galactic feedback, is an important component of cosmic ecosystems, shaping how galaxies evolve and affect the large-scale structure of the Universe. I will argue that flexible analytic models for the multiphase CGM are useful for fitting a wide range of multiwavelength observations and inferring the underlying gas properties, which can then be related to galaxy evolution, accretion and feedback processes, and gas small-scale physics. I will review recent results addressing the warm/hot phase of the CGM and describe ongoing work on the cool and intermediate-temperature phases, coupled with models for the virialized gas. I will then discuss how these combined, holistic models can help us prepare for the next generation of instruments and observatories, from small to large, including the Habitable Worlds Observatory.