> but I've found that Claude, at least

You hit on a very important point here. The linked AGENTS.md is a bad idea for general purpose use because the things it's meant to tackle, including an inherent bias towards or against DRY, is one of the big differences between model families. GPT 5.4 Codex has a very different "coding personality" from Claude Opus.

It's a product of whatever model it was tested on.