Definition
Merkleize All The Things, abbreviated MATT, is an experimental research approach for general smart contracts on Bitcoin, developed by Salvatore Ingala. The name was coined at the BTCAzores unconference. MATT is not a consensus feature; it describes a design that would be enabled by adding a small number of covenant opcodes through a soft fork. We summarize it here for readers following Bitcoin's contracting research.
The core idea
MATT requires no cryptographic primitive beyond Merkle trees. Contract state is committed in a Merkle root attached to a UTXO; transitions are enforced by covenants that constrain the spending transaction's outputs to carry a valid next state. Because computation is broken into small verifiable steps, complex programs can be settled on-chain through an interactive bisection (challenge-response) protocol that narrows a disputed computation down to a single step Bitcoin can check directly.
Design goals
Ingala highlights several intended properties: small impact on Layer 1, no application-specific opcodes, a clean fit with Pay-to-Taproot, and no new cryptographic assumptions. A rough vault implementation comparable to OP_VAULT-style designs has been sketched on the MATT model. In practice, much of MATT's generality can be reached with just OP_CHECKCONTRACTVERIFY plus OP_CAT. As with all covenant work, the community continues to weigh expressiveness against base-layer simplicity in a constructive, ongoing discussion.
MATT relates closely to OP_TXHASH and shares its dispute-resolution style with optimistic systems like BitVM2.
In Simple Terms
Merkleize All The Things, abbreviated MATT, is an experimental research approach for general smart contracts on Bitcoin, developed by Salvatore Ingala. The name was coined…