Chandra X-ray light curve of GRB 170817A (black points), including our new observations at 109.2 days post-burst. The predicted X-ray light curves from the cocoon model of Gottlieb et al. (2017; solid orange line), the cocoon (solid red line) and ejecta (solid blue line) outflow models of Mooley et al. (2017), and the structured jet model of Lazzati et al. (2017b) are also shown. The gray shaded region is the timespan over which Chandra observations were not possible due to Sun constraints. All uncertainties shown are 90% confidence intervals. The brightening X-ray light curve is well described by cocoon, dynamical ejecta, or structured jet models, although several of these models underpredict the detected early X-ray flux at 9 days post-burst.