Apollo Kotlin 4 is a new major version of the Apollo Kotlin library, which builds upon Apollo Kotlin 3 and introduces various tooling and API improvements. The library now includes a brand new IDE plugin for refactoring needs, improved error handling APIs, WasmJs support, a multiplatform GraphQL parser, semantic nullability, network monitoring API, and more. For users of Android Studio or IntelliJ, the library is available as an IntelliJ plugin that provides features such as on-the-fly code generation, GraphQL navigation, and unused field inspection. The library's core APIs are now stable, with a goal to roll out smaller updates in the future. Apollo Kotlin 4 also introduces support for WasmJs, enhances nullability handling with experimental directives, and includes new features such as @oneOf support and WebSocket APIs. The community is encouraged to join the conversation on GitHub, community forums, and the Apollo KotlinLang slack channel.