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? 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 teenage students' perceptions of tasks in an intercultural, blended language learning project that has drawn over 15,000 participants since 2012.