Many U.S. school districts now rely on instructional coaching to promote reform. Yet facets of coaching policy remain vague, and there is considerable variation in the structures and practices of coaching. We use longitudinal, qualitative data to analyze changes in instructional coaching, as a capacity building policy instrument, in one mid-sized urban-emergent school district from 2014 to 2019. Applying concepts of organizational learning theory, this paper documents how district leaders designed and implemented three distinct forms of coaching. We argue coaching shifted from a tool for teacher support, to a resource for school improvement, and lastly to a lever for boosting coherence. Further, we demonstrate how particular problems and leaders triggered different degrees of organizational learning on--and changes to--coaching. In sum, the paper explains how a district alters the definitions and structures of instructional coaching. By illuminating how educational leaders tinker with capacity building instruments, this paper contributes to the instructional reform literature and advances the field's understanding of the evolution of capacity-building instruments.