user2787: I can think of one solution, which is the validator script checks if a specific NFT is locked by the script address. Because of the nature of the NFT, it ensures there is at most one UTxO sitting at the script address at any given time that can also be consumed.
This is to ensure there is a chain of UTxOs sitting at the script address without forking.
I wonder if there are any other solutions.

user2248: Yes, you can use a policy id as a parameter to that script and say that the script can only be consumed if it contains a token with that policy ID. You then mint an NFT and send it to this script (which should have the policy ID from your NFT as a parameter).
Since NFTs are unique, this will be the only UTxO that can be consumed, because the rule enforces that the script can only be consumed if it has that specific unique token.

2787: <p>I can think of one solution, which is the validator script checks if a specific NFT is locked by the script address. Because of the nature of the NFT, it ensures there is at most one UTxO sitting at the script address at any given time that can also be consumed.</p>
<p>This is to ensure there is a chain of UTxOs sitting at the script address without forking.</p>
<p>I wonder if there are any other solutions.</p>
 2248: <p>Yes, you can use a policy id as a parameter to that script and say that the script can only be consumed if it contains a token with that policy ID. You then mint an NFT and send it to this script (which should have the policy ID from your NFT as a parameter).</p>
<p>Since NFTs are unique, this will be the only UTxO that can be consumed, because the rule enforces that the script can only be consumed if it has that specific unique token.</p>
