Our first covenant-specic opcode proposal, OP_CheckTemplateVerify — or “CTV” as it’s commonly referred to — aims to create a very specific, restricted, covenant opcode by doing exactly one thing: hashing the spending transaction in a specified way that does not commit to the input UTXOs, and checking the resulting digest against the top stack element. This allows the spending transaction to be constrained in advance, without making true recursive covenant restrictions possible.