feature-flag.txt
Put this new feature behind a switch: <describe the feature>

- Off by default. On for me, so I can test it in the real thing.
- One place in the code that decides — not a check scattered
  everywhere.
- Both paths must work. Show me how I'd verify that.
- Tell me how I'd remove the flag afterwards, and put a note in the
  code saying when it should go.

Flags left in forever become a maze of conditions nobody dares delete. Decide the removal date when you add it.