Udi is at it again this time with OP_CAT. Specifying conditions under which Bitcoin can be spent in the future, covenants can be used in areas like automated payments and "reversible transactions".

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Bitcoin Proposal to Restore Satoshi Code Gets a '420' Update - Decrypt

OP_CAT, which could enable advanced functionality on Bitcoin, was introduced as BIP-420 by Taproot Wizards co-founder Udi Wertheimer.