The Sentry JavaScript SDK underwent significant changes in version 7 to reduce its bundle size by 29%, from 74.47kb to 52.67kb, while maintaining a manageable bundle size and supporting future feature development. The refactoring involved breaking changes to developers who wrote their own integrations, but the new roadmap ensured that major updates would not change or remove parts of the Public API. To track progress, metrics such as minified CDN bundle size were measured using the `size-limit` library, and tree shaking capabilities were introduced to allow users to remove unnecessary code. The changes included enabling tree shaking for transports, integrations, and stacktrace parsers, adding magic strings that enabled users to configure with bundlers, and removing unnecessary abstractions. The results showed a significant decrease in bundle size, with Next.js SDK users reporting a 30kb reduction in run-time JavaScript, and no confirmed bug reports after the release of version 7 due to emphasis on integration testing and not changing the Public API.