It’s magical incantations that might or might not protect you from bad behavior Claude learned from underqualified RL instructors. A classic instruction I have in CLAUDE.md is „Never delete a test. You are only allowed to replace with a test that covers the same branches.“ and another one „Never mention Claude in a commit message“. Of course those sometimes fail, so I do have a message hook that enforces a certain style of git messages.

Way too many agent prompt files are just fan fiction or D&D character background documents that have no actual effect on what the agent does =)