This is the Symfony Security Core component, a pure PHP library providing a generic, extensible authorization and authentication framework. It is infrastructure code, not an application – it defines interfaces and implementations for token storage, access decision making (with pluggable voters and strategies), role hierarchies, user providers and checkers, signature hashing for secure links, and validation constraints. The architecture relies heavily on design patterns: Strategy (access decision strategies), Chain of Responsibility (user providers/checkers), Decorator (traceable managers, usage tracking token storage), and Template Method (abstract Voter class). It is well-typed with PHP 8.4 features and includes extensive unit tests. The repository also bundles 50+ locale translations for security-related exception messages. It is a mature, actively maintained component that forms the security foundation for Symfony applications.