Lisa Matthias, Juan Pablo Alperin, Mikael Laakso
While much attention has been paid to journals transitioning toward Diamond Open Access (OA), comparatively little is known about those moving in the opposite direction. We introduce the concept of "diamond fractures"--instances in which journals that once published freely for both readers and authors subsequently abandoned that model, transitioning to subscription-based or article processing charge (APC)-funded publishing. Drawing on publisher OA portfolio records, historical APC lists, removal logs from the Directory of Open Access Journals, and a survey of journals using Open Journal Systems, we identified and characterized more than 440 journals that have undergone such fractures and analyzed how they are distributed across publisher types, disciplines, and regions; which models journals transition to and at what price points; how old journals are when they fracture; and how publication volume shifts in the period surrounding the transition. This paper reports on more than 440 confirmed fractures, the majority of which involve transitions to charging APCs, ranging from $8 to $5,300. These findings raise urgent questions about the stability of diamond OA as a publishing ecosystem. The transition to APCs--even at initially modest price points--follows well-documented warnings about the hyperinflationary tendencies of author-pays models, in which charges introduced as a pragmatic stopgap have repeatedly escalated over time. The rate of fractures are likely to intensify as APC-based publishing continues to be normalized through funder mandates and commercial OA incentives. Diamond fractures demand to be treated not as isolated institutional decisions but as a systemic risk--one that can only be addressed through sustained investment in community-governed infrastructure and funding models that reduce the conditions under which abandoning diamond OA becomes the path of least resistance.