Does "fear of touching old code" disappear with agents, or just move?

Since agents will happily rebuild anything you ask in minutes, "I'm afraid to touch this" stops meaning what it used to. But I don't think the fear goes away, it just moves.

I keep a section in my CLAUDE.md that isn't architecture notes, it's just "already tried this, here's why it didn't work." Without it the agent will quietly rebuild the same mistake in 3 months, because it has no memory of the first time and the code looks perfectly reasonable on its own.

Anyone else keeping something like this, or is architecture memory basically a prompt-engineering problem now?