Bitcoin Covenant Design MATT Uses OP_CCV to Carry Dynamic State Across Taproot UTXOs

The Merkleize All The Things framework, known as MATT, outlines a mechanism to introduce stateful smart contracts and scalable fraud proofs to $BTC by preserving contract state across successive transactions ¹. Published in a technical analysis on Nov. 11, 2026, the proposal centers on an opcode designated as OP_CHECKCONTRACTVERIFY (OP_CCV), which allows Bitcoin scripts to dynamically compute and re-embed execution state into Taproot outputs at spend time ¹.

Standard Bitcoin transactions operate without native execution memory, evaluating each script independently ¹. While earlier covenant models such as OP_CHECKTEMPLATEVERIFY (OP_CTV) can represent finite state systems using distinct addresses, they struggle to process numerical logic dynamically ¹. In contrast, MATT alters the Taproot internal key using elliptic curve point math, tweaking public keys via $Q = P + t \cdot G$, where the tweak $t$ commits to a hash of the contract's execution data alongside the standard taptree spending paths ¹. By verifying these tweaks, OP_CCV forces a spending transaction to carry validated state forward into subsequent outputs ¹.

Value Preservation and Opcode Modes

Under the proposed specification, OP_CCV operates across three output inspection modes: default, deduct, and ignore ¹. Default mode commits the total input value to the designated output, while deduct mode allows partial allocations, and ignore mode enforces state commitments without constraining transaction amounts ¹.

Because default and deduct modes preserve output value, network fees must be supplied using separate inputs and change outputs, preventing the accidental burning of funds common to static covenant constructions ¹. When paired with OP_CAT to handle byte concatenation, the framework facilitates onchain verification of Merkle trees, establishing the foundation for interactive fraud proofs ¹. At the time of writing, $BTC traded at $73,636.