tl;dr - author cites a study from early 2025 which measured developer speed of “experienced open source developers” to be ~20% slower when supported by AI, while they’ve estimated to be ~20% faster.

Note: the study used sonnet-3.5 and sonnet-3.7; there weren’t any agents, deep research or similar tools available. I’d like to see this study done again with:

1. juniors ans mid-level engineers

2. opus-4.6 high and codex-5.2 xhigh

3. Tasks that require upfront research

4. Tasks that require stakeholder communication, which can be facilitated by AI