Bitcoin Covenants Part 5: MATT and OP_CHECKCONTRACTVERIFY — How Bitcoin could carry state across transactions
Summary
MATT is a proposed framework for Bitcoin stateful contracts, using Taproot commitments to carry contract data across transactions. Its OP_CHECKCONTRACTVERIFY (OP_CCV) implementation can enforce updated state in later outputs and offers flexible value handling, with separate fee inputs. Combined with OP_CAT, MATT could verify Merkle proofs on-chain, enabling fraud-proof systems in which only disputed computation steps are revealed. The combination may also support advanced vaults, with the piece describing it as a broader alternative to OP_VAULT. These capabilities depend on proposed Bitcoin opcodes rather than currently available standard scripts.
