3,500+ Downloads Later: The Engineering Behind the eyeris R package eyeris [1][2] – a CRAN-published R package for reproducible pupillometry preprocessing with BIDS compliance, automated QC reports, and scalable pipeline tools. Building for Reproducibility and Scale When designing eyeris , I faced a unique engineering challenge: create a system that's both user-friendly for researchers with minimal programming experience, yet powerful and extensible enough for advanced computational users. Here's how I solved several key technical problems. Architecture: The Pipeline Pattern Design Philosophy The core architectural pattern in eyeris is a functional pipeline where each preprocessing operation: Takes an eyeris object as input Applies a transformation to the pupil timeseries data Records its parameters and provenance Returns the modified eyeris object This enables both pipe-based workflows ( %>% or |> ) and function composition while maintaining full traceability.…