OP_CHECKTEMPLATEVERIFY (CTV)

OP_CHECKTEMPLATEVERIFY (CTV), specified in BIP 119 by Jeremy Rubin, is a proposed Bitcoin opcode that commits an output to a specific spending-transaction template. When a coin locked with CTV is spent, the opcode hashes a defined set of fields of the spending transaction — the outputs, the number of inputs, the sequence numbers, and similar data — and checks that hash against a 32-byte value baked into the locking script. If the hashes do not match, the spend fails. In plain terms: the coin can only ever move by way of a transaction whose shape was decided in advance. CTV is a proposed soft fork; it is not active on mainnet and remains under community review.

Deliberately limited by design

CTV provides the narrowest useful form of transaction introspection. Because the template is a fixed, fully enumerated hash rather than a programmable expression, CTV produces non-recursive covenants with no dynamic state: a coin can be forced to flow into a predetermined next transaction, but that next transaction cannot itself impose arbitrary new rules invented on the fly. There is no loop, no unbounded chain of restrictions that could follow a coin forever. This restraint is intentional. Much of the covenant debate concerns whether more expressive introspection could enable undesirable constructions; CTV's answer is to offer the smallest primitive that still unlocks real applications, which is why it is often described as one of the more conservative covenant designs on the table.

What it enables

Pre-committing to where coins must go turns out to be surprisingly powerful. Self-custody vaults become practical: a vault can enforce that withdrawals first pass through a time-delayed staging output, giving the owner a window to claw funds back to cold storage if a key is compromised. Congestion-control transaction trees let an exchange or pool commit to hundreds of payouts behind a single on-chain output during high-fee periods, with recipients unfolding the tree later when block space is cheap — see the congestion control tree entry for the mechanics. CTV also supports payment pools where multiple parties share a UTXO with guaranteed exit paths, and more efficient Lightning channel constructions. All of this happens through a pure hash comparison, without exposing keys to new signing modes or adding heavy computation to validation.

Why miners and sovereignty builders watch it

Covenant proposals matter to the mining and self-custody world for two reasons. First, constructions like congestion-control trees change fee-market dynamics: they smooth demand spikes by letting large payout events defer their block-space consumption, which affects the fee environment every miner sells into. Second, vault-style covenants strengthen the practical security of holding your own keys — the core sovereignty act Bitcoin exists to protect. A future where a home miner's block reward or pooled payout can land directly into a covenant-protected vault is a future where self-custody is safer for ordinary people, not just for those who can operate elaborate multisig ceremonies.

Status and context

CTV has been implemented, tested on signet, and debated for years, but Bitcoin's consensus process is deliberately slow and no activation is scheduled. It is frequently discussed alongside the general idea of a covenant and against alternative introspection proposals that trade more expressiveness for more risk surface. D-Central presents this as an explanation of an open proposal, not an endorsement of any activation path: understanding what CTV does — and pointedly does not do — is the prerequisite for having an informed opinion when the debate reaches your node.

For builders who want hands-on understanding rather than mailing-list opinion, CTV can be exercised today: implementations have run on custom signets, and a patched regtest node lets you construct template commitments and watch non-matching spends fail. Nothing about the opcode requires trusting its designers — the behavior is small enough to audit in an afternoon, which is itself part of the argument its proponents make for it.