From the economic to the political, from public health to the climate, models seem to run the world. In architecture, the model is no longer just a physical tool for conceptualizing or representing architects’ visions but must also encompass digital and 3D-printed models, data and artificial intelligence models, business models, educational models, and even engage the discipline’s own questionable history in establishing role models. A thematic issue, Log 50: Model Behavior interrogates models in this expanded sense: what are their values, their behaviors, and the behaviors they elicit. In a record-setting 256 pages, 39 authors, ranging from established architectural thinkers to up-and-coming practitioners, examine the role of the model in architecture today through critical essays, conversations, observations, projects, and provocations.