typelevel/cats-effect

Cats Effect is a functional programming library that provides a unified, cross-platform runtime for managing asynchronous effects and concurrency. It implements a high-performance, work-stealing scheduler and a structured concurrency model that supports JVM, JavaScript, and Native targets. The system exposes a comprehensive set of typeclasses and standard library components for resource management, state, and I/O, while offering robust tooling for testing and migration.

This period focused on the complete rewrite of the IO runtime and concurrency model, introducing a new `IORuntime` configuration system and replacing legacy abstractions like `Bracket` and `Concurrent`. The work heavily emphasized cross-platform compatibility, adding specific implementations for JVM, JavaScript, and Native targets, alongside comprehensive test coverage and performance benchmarks.

29 changes

The project expanded its runtime capabilities by introducing full support for Scala Native, including core execution, polling systems, and tracing infrastructure. Concurrently, the team enhanced observability by adding comprehensive JVM metrics and MBean interfaces, while also providing automated migration tools for Cats Effect 3.0 and 3.3 API changes.

37 changes

This period focused on extending Cats Effect's capabilities to the Native platform, including new unsafe queue implementations, signal handling, and comprehensive test suites for concurrency and timing. Concurrently, the project migrated its testing infrastructure from specs2 to munit and added extensive platform-specific tests for JVM, JavaScript, and Native targets.

21 changes

typelevel/cats-effect was measured the same way every project in this corpus was: the same rubric, at a pinned commit, with the result published in full. Point the surveyor at a repository you know and see whether you agree with it.