Multiple programming tasks require synchronous collaboration between developers, giving rise to real-time collaborative programming tools that enable simultaneous editing of shared source code. However, most existing tools operate at the text level, propagating every keystroke–including syntactically invalid ones–without considering program structure. This results in excessive communication overhead, frequent propagation of build-breaking states, and poor synchronization. A major consequence is noticeable lag, especially under unstable network conditions, as collaborators are overwhelmed with unnecessary updates that disrupt their workflow and degrade the shared coding experience. In this paper, we introduce a novel structure-aware propagation model that transmits only syntactically valid code changes. For evaluation we implemented our tool as an IntelliJ plugin and evaluate it against three industry-standard tools–VS Code Live Share, Code With Me, and Replit–across eight representative programming scenarios. Our results show that it significantly lowers the number and size of propagated messages while maintaining consistent, buildable program states. Our findings demonstrate the potential of structure-aware propagation as a foundation for the next generation of real-time collaborative programming environments.