On Sun, Jul 4, 2021 at 9:02 PM Russell O'Connor <roconnor@blockstream.com> wrote:

Bear in mind that when people are talking about enabling covenants, we are talking about whether OP_CAT should be allowed or not.

That said, recursive covenants, the type that are most worrying, seems to require some kind of OP_TWEAK operation, and I haven't yet seen any evidence that this can be simulated with CHECKSIG(FROMSTACK). So maybe we should leave such worries for the OP_TWEAK operation.

Upon further thought, you can probably make recursive covenants even with a fixed scritpubkey by sneaking the state into a few bits of the UTXO's amount. Or if you try really hard, you may be able to stash your state into a sibling output that is accessed via the txid embedded in the prevoutpoint.