Bitcoin Covenants Part 5: MATT and OP_CHECKCONTRACTVERIFY — How Bitcoin could carry state across transactions

Bitcoin's proposed OP_CHECKCONTRACTVERIFY (OP_CCV) embeds contract state directly into Taproot output keys, enforcing valid state transitions onchain. This enables stateful contracts and compact fraud proofs, potentially expanding Bitcoin's capabilities beyond simple transfers. The proposal is part of ongoing research into Bitcoin covenants, which could unlock advanced smart contract functionality.