EXIST consists of the High Energy Telescope (HET), a system of coded-mask sub-telescopes with CZT detector planes, and the Optical-IR Telescope (IRT). The HET uses CsI anti-coincidence shielding to reduce the particle-induced background. This active shielding can also be used to detect photons up to roughly 20 MeV, with spatial resolution roughly equal to the collimation of each HET sub-telescope. The configuration of the telescopes is evolving rapidly, and a new baseline will be posted here in the near future.