Zod 4 has been released, bringing a host of changes, but its migration guide highlights numerous breaking changes which may pose significant challenges for developers relying on this library. Many comments express concerns about the arduous task of adapting existing projects due to these changes, especially in large applications that depend on multiple libraries. There is also a discussion about the need for better documentation, as transitioning between library versions can be overwhelming without clear guidance. Alternatives like ArkType are mentioned, noting that they offer better performance and TypeScript ergonomics compared to Zod. Some users suggest exploring JSON-Schema solutions to cope with validation needs. Overall, the anxiety surrounding maintenance of tools in the JavaScript ecosystem, compounded by the difficulties in dependency management and having to validate data across different environments, remains a prevalent theme.