Apollo Client 2.5 is a new version of the popular GraphQL client library that introduces local state management, allowing developers to manage data locally without relying on a remote server. This feature enables developers to define their own data schema and resolvers for local data, which can be queried alongside remote data using GraphQL. The introduction of local state management also brings several other improvements, including enhanced developer tooling, such as autocomplete in editors like Apollo VS Code, automatic type definitions with the Apollo CLI, and improved debugging tools. Additionally, Apollo Client 2.5 includes new features such as code splitting, local subscriptions, and an `@export` directive for loading values from local state into remote queries. The library's bundle size has also been reduced to offset the new features. With these updates, developers can now build more complex applications with improved performance and maintainability.