Are AI instruction files like CLAUDE.md or cursor rules a bad idea?
No. They are genuinely useful for orientation: where things live, how to run the tests, what the conventions are. The problem is only when they take on architectural constraints, because prose cannot enforce anything and the file grows without limit.
From The thousand-line prompt problem, published 9 August 2026. That article is where the reasoning behind this answer is set out, including what it does not cover.