AI writes code fast now. So what's the new bottleneck?
AI writes code fast now. So what's the new bottleneck?
On a16z, the answer starts with how small most code changes already were. The average PR at a large company is about ten lines. Automate the small part and the work moves. At Newsela it moved to code review: CTO Dee Wilcox watched review time go from one day to four as PRs grew to 1,500 lines. At that volume people skim. Maggie Appleton says it plainly: once you know what to build, which is all the work, you skim, skim, skim and merge. OpenAI's Tibo Sottiaux hires for taste now, not typing speed.
Code got cheap. Deciding what to build and checking what got built did not. If you track one number on your engineering team this quarter, make it review time.
Sources: a16z, "AI Can Write Code. Why Isn't Software Better?," Sep 28, 2026. Dee Wilcox (Newsela), Dev Interrupted, "Why AI made code review the new bottleneck, and the metric that spotted it," Sep 29, 2026. Maggie Appleton, The Pragmatic Engineer, "Design Engineering with Maggie Appleton," Sep 23, 2026. Tibo Sottiaux (OpenAI), Lenny's Podcast, "OpenAI's Head of ChatGPT: We're entering a new era of AI (again)," Oct 4, 2026.