Vata (Kru, Ivory Coast) has two distinct processes of ATR harmony. Within words, harmony is unblocked, obligatory, and not subject to directional restrictions. Across word boundaries, however, harmony is optional, directional (right-to-left), and subject to blocking by certain height configurations. Additionally, it is non-iterative into polysyllabic words, but iterative across sequences of monosyllabic words. In Alignment-based theories of domain bounding, these facts are problematic because they represent paradoxical strength relationships; harmony across junctures is able to create forms inconsistent with within-word harmony, and yet is subject to more stringent restrictions. In this paper, I show how a theory of domain bounding which is (a) based on constraints that are sensitive to the location of a feature's head and (b) situated in Harmonic Serialism (a derivational version of Optimality Theory) is able to provide an account of both the facts in Vata and the crosslinguistic range of juncture harmony processes.