AI slows down open source developers. Peter Naur can teach us why

Summary

AI slows down open source developers. Peter Naur can teach us why.AI slows down open source developers. Peter Naur can teach us why. Metr recently published a paper about the impact AI tools have on open-source developer productivity1. They show that when open source developers working in codebases that they are deeply familiar with use AI tools to complete a task, then they take longer to complete that task compared to other tasks where they are barred from using AI tools. Interestingly the developers predict that AI will make them faster, and continue to believe that it did make them faster, even after completing the task slower than they otherwise would! When developers are allowed to use AI tools, they take 19% longer to complete issues—a significant slowdown that goes against developer beliefs and expert forecasts. This gap between perception and reality is striking: developers expected AI to speed them up by 24%, and even after experiencing the slowdown, they still believed AI had sped them up by 20%. Measuring the Impact of Early-2025 AI on Experienced Open-Source Developer Productivity We can't generalise these results to all software developers. The developers in this study are a very particular sort of developer, working on very particular projects. They are experienced open source developers, working on their own projects. This study tells us that the current suite of AI tools appear to slow such developers down - but it doesn't mean that we can assume the same applies to other developers. For example, we might expect that for corporate drones working on a next.js apps that were mostly built by other people who've long since left the company (me) see huge productivity improvements! One thing we can also do, is theorise about why these particular open source developers were slowed down by tools that promise to speed them up. I'm going to focus in particular on why they were slowed down, not the gap between perceived and real performance. The inability of d...