Drawing upon scholarship on cultural-historical activity theory and writing across difference, this study investigated how students reflect on critical incidents in writing-intensive courses that are expansive by design, that is, spanning courses, semesters, communities, and cultures, and seeking to orient students toward critical incidents as catalysts for expansive learning. Findings indicate that students who reported valuing/understanding critical incidents in developing more expansive conceptualizations of literate activity tended to be further along in their studies, to be enrolled in courses with more reflective writing and semester-long community-engagement projects, and to have assumed significant team responsibilities. Students most frequently reported finding helpful concepts and design elements associated with the expansive-by-design classroom, and least helpful prior knowledge, skills, and experience (or lack thereof). The authors recommend more research into designing and assessing curricula bolstered by a writing across difference framework to illuminate the relationship between agency, sociocritical literacy, critical incidents, and expansive learning.