Which Sustainability? <scp>EU</scp> Multilevel Governance

ABSTRACT This paper examines how sustainability is framed, coordinated, and operationalised across the three levels of European Union (EU) multilevel governance (MLG) by analysing 3466 non‐legislative documents produced between 2011 and 2021 by the European Parliament (EP), the Council of the European Union (Council), and the Committee of the Regions (CoR). Employing the BERTopic method, complemented by a curated sustainability lexicon and systematic validation of topic coherence and intercoder reliability, the analysis identifies distinct institutional portfolios. Specifically, the CoR predominantly emphasises environmental issues and locally implementable themes, the Council primarily addresses societal concerns, and the EP advances a cross‐cutting agenda that links environmental and socio‐economic instruments to the Sustainable Development Goals (SDGs) and the European Green Deal. The paper further traces inter‐institutional references and shared narratives, revealing coordination gaps within EU MLG. From a methodological perspective, BERTopic is a topic‐modelling approach that combines transformer‐based language models with class‐based term frequency–inverse document frequency (TF‐IDF) to generate dense document clusters. This approach yields highly interpretable topics while preserving salient terms in topic descriptions, thereby significantly enhancing interpretability beyond simple word‐frequency techniques. Conceptually, the article situates EU sustainability framings within the broader literatures on governance and performance. Overall, the study contributes a reproducible mapping of sustainability across EU multilevel governance and derives implications for policy coherence, division of labour, and the early involvement of sub‐national actors. The article's added value lies in its integration of machine‐learning‐based analysis—specifically BERT‐based topic modelling—with a traditional expert‐driven analytical approach to EU multilevel governance, including policy analysis and examination of the acquis communautaire .