Recent research shows that negotiation of meaning in online task-oriented interactions can be a catalyst for L2 (second/foreign/additional language) development. However, how learners undertake such negotiation work and what kind of an impact it has on interactional development in an L2 are still largely unknown mainly due to a lack of focus on task engagement processes. A conversation analytic investigation into negotiation of meaning (NoM) in task-oriented interactions can bring evidence to such development, as conversation analysis (CA), given its analytic tools, allows us to see how participant orientations in interaction evolve over time. Based on an examination of screen-seconded multiparty online task-oriented interactions, this study aimed to describe how users (n = 8) of an L2 (1) negotiate and co-construct language and task rules and (2) later show orientations to these rules both in the short term (50 minutes) and in the long term (8 weeks). The findings showed that in addition to negotiating existing rules, the learners co-constructed new rules around an action called policing, which occurred when the learners attended to the breach of language and task rules. Furthermore, even after the negotiation work was completed, they oriented to negotiated rules through policing their own utterances (i.e. self-policing). Overall, this interactional continuum (from other-repairs to self-repairs) brought longitudinal evidence to bear on the role of NoM in the development of L2 interactional competence. These findings bring new insights into NoM, technology-mediated task-based language teaching (TBLT), and CA for second language acquisition (SLA).