Escaping the Fork: How Meta Modernized WebRTC Across 50+ Use Cases

This post details Meta's migration from a divergent WebRTC fork to a modular architecture based on the latest upstream version. Key contributions include the development of a dual-stack architecture with a shim layer for A/B testing, enabling runtime dispatch between legacy and latest WebRTC versions. This was achieved through automated C++ namespace renaming, handling of global symbols and macros, and a template-based helper library for version-specific logic. A code generation system was built to automate shim creation. The migration involved rewiring application references and using Buck build machinery to duplicate components for dual-stack builds, ultimately reducing binary size by 87% and enabling continuous upstream upgrades.