How does foreign language learners' agency emerge at the micro-level of classroom activity during the enactment of digitally-enhanced tasks, and how do these learners exercise their agency digitally within and beyond the classroom? Drawing on research in task-based and computer-assisted language learning, this mixed-methods study uncovers key dimensions of "learner agency" - a newcomer to the field of language teaching methodology and applied linguistics. The analysis centers on three case studies of teenage students' perceptions and handling of digitally-enhanced language learning tasks. These are complemented with a Germany-wide questionnaire survey among participants in the U.S. Embassy School Election Project - an intercultural, blended language learning project that has drawn over 15,000 participants since 2012.