React Native's Bridgeless Mode Replaces the Bridge with Direct JS-to-Native Calls

React Native's New Architecture introduces Bridgeless Mode, which eliminates the legacy Bridge that forced JavaScript and native code to communicate via serialized JSON messages over an asynchronous queue. The old system caused serialization overhead, unpredictable UI update timing, and fixed startup latency — problems that were especially costly in performance-sensitive applications like clinical AI platforms handling real-time medical data. Bridgeless Mode is built on the JavaScript Interface (JSI), which lets the Hermes JavaScript engine hold direct references to C++ objects and call native methods synchronously without a message queue. This underpins two key systems: Fabric, a synchronous rendering engine, and TurboModules, a lazy-loading native module system, both of which help React Native apps achieve responsiveness closer to fully native applications. However, the transition is disruptive, as many third-party libraries built for the legacy Bridge require significant rework before they are compatible with the new architecture.