XState

XState is a TypeScript-first library for managing complex application logic through finite state machines and statecharts.

David Khourshid built XState to bring mathematical certainty to frontend state management. It follows the SCXML (State Chart XML) specification to eliminate 'impossible states' by defining explicit transitions: ensuring your app only moves from one valid configuration to another. Developers at companies like Microsoft and Netflix use it to orchestrate intricate flows (multi-step checkouts or complex UI animations) across React, Vue, and Node.js environments. The library pairs with the Stately Editor to visualize logic: bridging the gap between design diagrams and production code. It handles parallel states, history, and invoked promises with zero ambiguity.

https://stately.ai/docs/xstate