This is the fifty-eighth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with the 3.6.x lineage.

[!WARNING] Please note that Cats Effect 3.6.x is targeting Scala Native 0.4.x, which means it does not at present support native multithreading. This was a very intentional choice meant to give us an opportunity to break binary compatibility only on Scala Native if necessary when upgrading to Scala Native 0.5 and as we discover the impacts of the integrated runtime on the downstream ecosystem. It also reduces risk since Native multithreading in the runtime is a significant lift and we want to make sure we isolate that change from the already significant changes in 3.6.0. This functionality has already merged into the development branch and we plan to release it in 3.7.0 as soon as possible.

What's Changed

This release fixes a pretty nasty bug introduced in 3.6.2 which frequently results in the thread pool being entirely poisoned, producing severe performance degradation that could only be resolved by restarting the process. It is highly recommended that all users on 3.6.2 upgrade to 3.6.3 as soon as possible.

Bug Fixes

• Fix the spinlock from #4377 and probably also fix #4448 by @durban in https://github.com/typelevel/cats-effect/pull/4449

Full Changelog: https://github.com/typelevel/cats-effect/compare/v3.6.2...v3.6.3