What is a regression in software development?
A regression is a change that breaks something which previously worked, usually a feature nobody meant to touch. The change itself often looks correct and passes review; the damage surfaces elsewhere, through shared code, and later, when someone finally exercises the broken path. AI-assisted development produces the classic regression pattern at much higher speed.
From Why AI keeps breaking features that already worked, published 20 August 2026. That article is where the reasoning behind this answer is set out, including what it does not cover.