In this article, we provide longitudinal evidence for the progressive routinization of a grammatical construction used for social coordination purposes in a highly specialized activity context: task-oriented video-mediated interactions. We focus on the methodic ways in which, over the course of 4 years, a second language speaker and initially novice to such interactions coordinates the transition between interacting with her coparticipants and consulting her own screen, which suspends talk, without creating trouble due to halts in progressivity. Initially drawing on diverse resources, she increasingly resorts to the use of a prospective alert constructed around the verb to check (e.g., "I will check"), which eventually routinizes in the lexically specific form "let me check" as a highly context-and activity-bound social action format. We discuss how such change over the participant's video-mediated interactional history contributes to our understanding of social coordination in video-mediated interaction and of participants' recalibrating their grammarfor-interaction while adapting to new situations, languages, or media. Data are in English.People coordinate their social interaction with others through the use of mutually recognizable practical procedures for action-that is, "methods" in the ethnomethodological sense of the term (Garfinkel, 1967). Based on these procedures, they manage fundamental organizational issues such as turn-taking, sequencing of actions, and opening or closing conversation. Methods develop experientially over time, based on people's repeated engagement in locally accomplished social interactions , and so do the multisemiotic resources deployed as part of these methods. Methods and the related resources, the sharedness of which warrants mutual accountability of social actions (Garfinkel, 1967), constitute people's interactional competence.Existing longitudinal studies on the development of interactional competence in a first (L1) or a second/foreign/additional language (L2) across a range of different settings converge on evidencing that such development implies the progressive diversification of practices and resources for interaction (on L1 see, e.g., Wootton, 1997; on L2 see overviews by Pekarek Doehler & Pochon-Berger, 2015;Skogmyr Marian & Balaman, 2018). This diversification allows for increasingly context-sensitive and recipient-designed conduct (cf. Sacks & Schegloff, 1979;Sacks et al., 1974)-that is, conduct that is more and more acutely tailored to the precise situation and the precise others at hand (see also Skogmyr Marian, 2021/this issue).Such development is not just part of L1 or L2 learning but is constitutive of the very way we navigate our social lives. Our interactional histories bring about unprecedented types of social situations, which we enter as novices, progressively adapting our practices to the precise constraints CONTACT Simona Pekarek Doehler
