GenAI as a coding partner: Productivity gains at the cost of sustainability and maintenance

Generative AI solutions like GitHub Copilot have been shown to increase the productivity of software developers. Yet prior work remains unclear on the quality of code produced and the challenges of maintaining it in software projects. If quality declines as volume grows, experienced (core) developers face increased work-loads reviewing and reworking code from less-experienced (peripheral) contributors. We analyze developer activity in Open Source Software (OSS) projects following the introduction of GitHub Copilot. We find that productivity indeed increases. However, the increase in productivity is primarily driven by peripheral developers. We also find that code written after the adoption of AI requires more rework. Importantly, the added rework burden falls on core developers, who review 6.5% more code after Copilot’s introduction, leading to a 19% drop in their original code productivity. More broadly, this finding raises caution that productivity gains of AI may mask the growing burden of maintenance on a shrinking pool of experts.