Jasper Moeys enhanced error handling and debuggability across the Typelevel Scala ecosystem, focusing on the cats-effect and fs2 repositories. He introduced descriptive precondition error messages in core cats-effect utilities such as TestContext, Backpressure, and Queue, providing clearer context for failed preconditions and streamlining the debugging process. In fs2, Jasper improved error messaging for array slicing operations by adding specific require statements in ChunkPlatform.scala and Chunk.scala, making out-of-bounds errors easier to diagnose. His work leveraged functional programming and concurrency principles, resulting in more actionable feedback for users and supporting smoother onboarding and maintenance for these core libraries.