Toward a Program Theory of A Singaporean Single-Session, Synchronous Chat-Based Mental Health Support for Youths: The Behavior Change Techniques Workers Use and How They Relate to Outcome

Background: Text-based chat (TBC) services are among the most accessible mental health support for youth, yet more is known about whether they help than about how they help, that is, what workers do in sessions. Without an account of these worker skills, TBC services cannot be reliably trained for or evaluated. This study described the techniques chat workers use, drawing on the Behavior Change Technique Taxonomy (BCTTv1), and linked them to user- reported outcomes. Methods: We analyzed 1,439 real chat sessions (44,916 worker turns) from 73 workers at QuickChat, an anonymous, free, synchronous