Working with isolates in Flutter can quickly become complex, especially when passing messages and maintaining type safety. In this session, I’ll walk through how I built a code generator that simplifies communication across isolates by automatically generating strongly-typed stubs for classes running on separate isolates. This talk is also a practical deep dive into building a Dart code generator—from understanding the underlying tooling to designing an API that feels seamless for developers. I’ll share lessons learned from forking and extending an existing package, and how I evolved it into a more ergonomic solution. We plan to open-source this generator after the talk to share the approach and gather feedback from the community. Key Takeaways: Why isolate communication becomes a bottleneck in real-world Flutter apps (and how it forced us into a temporary “merged isolate” workaround) How to design and build a Dart code generator using source_gen/build_runner Techniques to preserve type safety across isolate boundaries How to redesign architecture to properly separate multiple isolates for better CPU and memory efficiency Lessons learned from extending and improving an open-source package