This hackathon-style event is an opportunity to collaborate on contributions to R, the widely used software environment for data science. Working in small groups, participants will analyse/propose fixes for bugs in the code or documentation of R (the base/recommended packages or the Windows/macOS GUIs); add/update translations of messages from English to other languages, or improve contributor infrastructure such as the R Dev Container (a Docker container providing an environment for R development) or the R Dev Guide (a Quarto-based online book). Participants will be selected by application to balance across experience levels. Thanks to RSECon25 sponsors and the R Dev Day sponsor, EPSRC, full scholarships to attend both RSECon25 and R Dev Day are available for participants from the Global South, while partial scholarships are available for participants from the UK and Europe. New and experienced contributors from any country are welcome to apply!