Cointelegraph Research describes MATT as a proposed framework for stateful Bitcoin contracts, not a feature available in standard Bitcoin scripts. Its most direct proposed implementation uses OP_CCV to check that a Taproot output commits to updated contract data, allowing a contract to carry state across transactions. The article says OP_CCV’s value-preserving modes require separate inputs to pay transaction fees.
Combined with the proposed OP_CAT opcode, OP_CCV could verify Merkle proofs for disputed steps in off-chain computations, supporting fraud proofs. The article says such proofs require the computation to be represented as steps that can be committed to in a Merkle tree.
