Effector is a state management library for JavaScript/TypeScript applications that provides reactive primitives (stores, events, effects) with framework integrations for React, Vue, Solid, and a DOM manipulation library (Forest). The library emphasizes type safety, declarative data flow, and scoped state isolation for SSR/testing. Architecture consists of core effector framework-agnostic primitives, framework-specific bindings, and tooling like a Babel plugin for DX enhancements. Key entry points include src/effector/index.ts (core API), packages/effector-react/index.ts (React bindings), and packages/forest/index.ts (Forest UI engine). Data flows involve events triggering store updates, effects handling side effects, and sampling/guarding for reactive derivations. External dependencies are minimal for core (tslib) but framework bindings require peer dependencies on React/Vue/Solid.