Strategy has become an important concern and practical tool in urban management and governance, with the literature highlighting implementation as a hallmark of effective strategy. Whilst such a strategy–action link (which we label here as ‘implementation nexus’) has been well established, other long-term effects have been documented in less detail. Our study of Sustainable Sydney 2030 finds that strategy was effective to the extent to which it changed the institutional a priori of what a collective of actors engaged in city-making knows, what it can articulate and how its members relate to each other. We capture this effect as ‘institution nexus’ and theorise our findings with Ludwik Fleck’s concept of ‘thought style’ of a focal ‘thought collective’ – notions that also centrally influenced Mary Douglas’ work on ‘how institutions think’. We contribute to extant research by adding the institution nexus as a long-term effect of urban strategy as well as by advancing strategy theory in urban studies to foreground its ability to shape institutions.