Scala 3.3 introduced the first Long-Term Support (LTS) release, setting expectations of stability, incremental improvements, and a predictable migration model - while innovation continued through the Scala Next release line.

Now, three years later, Scala 3.9 becomes the new LTS baseline, marking the next major migration point. But this cycle is fundamentally different: the compiler and tooling can now automate a large portion of migration effort, allowing teams to focus on product development rather than manual refactoring.

In this talk, I will present insights from running the Open Community Build, where we continuously build and migrate nearly 2,000 open-source projects to the newest Scala Next versions, from scratch, every week. This effort surfaces real-world compatibility issues long before they reach users, providing a unique perspective on how migrations behave at scale.

You’ll learn:

- How to approach migration to 3.9 LTS using compiler automation

- The most common problems observed when upgrading

- What breaks in practice, and how to fix it efficiently

- How Community Build feedback loops accelerate ecosystem stability

- Strategies for migrating libraries, applications, and whole ecosystems

This talk is not a feature overview of Scala 3.9, but a practical field report from running large-scale migrations every week. You will leave with a clear, repeatable migration strategy - and confidence that the compiler can handle more of the heavy lifting.