Drawing on positioning theory and Vygotsky's sociocultural theory of mind, this study analyzes the discursive processes through which expert and novice positions are negotiated in heritage-second language (HL-L2) learner interaction. It examines how positioning practices shape collaboration between HL and L2 learners, determining what types of learning opportunities are created and for whom. Data was collected in a high-intermediate Spanish language class with 8 HL and 10 L2 learners. As part of their regular course activities, learners completed four collaborative writing tasks in mixed dyads. Three HL-L2 interactions were selected as case studies. The combined analysis of discursive positioning, patterns of interaction, and language-related episodes showed how expert positions, often assigned to HL learners due to their heritage speaker status, constrain these learners' access to the linguistic feedback and help needed for HL development. When pre-established conceptions of linguistic expertise are challenged and HL learners are positioned as language learners, with knowledge to gain, and their L2 partners as equal peers, with knowledge to share, opportunities for HL development expand. The article discusses the research and pedagogical implications of these findings.