Innovative learning environments in engineering education—such as interdisciplinary learning, challenge-based learning, and living labs—require students to collaborate across disciplinary, cultural, and societal boundaries. This is essential for addressing complex, sustainability-related challenges. A key competence in these settings is boundary crossing: the ability to recognize, seek, appreciate and utilize tensions that emerge when diverse perspectives interact. Although many curricula strive to foster this competence, its assessment remains a significant challenge. Conventional assessment methods often fail to align with the open-ended, dynamic, and process-oriented nature of boundary crossing. Key issues include the diversity of intended learning outcomes, the need to balance disciplinary depth with transversal skills, and the difficulty of assessing developmental processes rather than end products. While reflective methods are commonly used, they also have limitations—for instance, the risk of superficial reflection and the emerging influence of AI tools on written outputs. This workshop invites participants to explore the why, what, and how of assessing boundary crossing competence in engineering education. Drawing on three realworld examples from a Life Sciences university in the Netherlands, participants will critically examine existing practices and co-create innovative assessment strategies tailored to their own contexts. Using interactive methods such as Think-Pair-Share and the collaborative digital tool Padlet, the workshop will foster dialogue and shared insight. Outcomes from the session will be collected and disseminated, with opportunities for continued exchange and collaboration beyond the event.