note 16
Don't keep unshipped backwards compatibility
Agents often build a feature and keep the old way working too. That is backwards compatibility. It saves you when a breaking change would take a live app offline. The agent is bad at deciding when it is worth keeping.
01
When it is worth it
Nothing is more painful than misjudging a breaking change and watching the whole app go offline. If people are already using the old way, say so. Keep it.
02
The agent cannot tell
It will keep the old path by default. It does not know whether anyone is using it, or whether you already changed your mind. That call is yours.
03
The feature that never shipped
You start a feature. Halfway through, you change direction. The agent still leaves the old version in place, just in case. Nobody ever used it. There is no customer to protect. Tell it to delete that path.
Keep backwards compatibility when someone is already using it. Drop it when the feature never shipped.