BIP 54 tightens four historical consensus edge cases without adding a new user-facing opcode; Complete means the specification is finished, not activated on Bitcoin mainnet.
Antoine Poinsot and Matt Corallo combined four narrowly scoped repairs in BIP 54: timewarp, blocks with extremely expensive validation, the Merkle-tree weakness around 64-byte transactions, and the future risk of duplicate coinbase transactions. The package adds no new user-facing opcode. [1]
At each 2016-block period boundary, the BIP requires the first block timestamp to be at least the previous block time minus 7 200 seconds and the final block timestamp to be at least the period's first block time. This closes both classic timewarp and a negative Murch–Zawy period. [1]
For every non-coinbase transaction it sets a ceiling of 2 500 legacy signature operations counted in scriptSig, scriptPubKey, and the P2SH redeemScript. The BIP says this cuts worst-case validation time by roughly fortyfold without affecting ordinary standard transactions. [1]
Transactions whose serialization without witness data is exactly 64 bytes would be invalid after activation. The same 64 bytes can otherwise be interpreted as the pair of hashes in an internal Merkle-tree node, complicating secure simplified proofs. [1]
The coinbase would need nLockTime equal to block height minus 1 and nSequence different from 0xffffffff. Every future coinbase then differs from historical exceptions, allowing the BIP 30 check to be skipped permanently after activation before the nearest risky height 1 983 702. [1]
The specification reached version 1.0.0 and Complete status in May 2026. Its changelog gives 22 May; Bitcoin Core has a reference implementation without mainnet activation and already creates more forward-compatible block templates, but none of that turns the new mainnet rules on by itself. [3]
Draft BIP 95 for Testnet 5 plans to enforce BIP 54 from block 1, but it is itself still Draft. A test network, signet, or inactive code can help verify an implementation; it is not evidence of mainnet consensus. [4]
To verify a claim, check the current BIP version, the status of any activation mechanism, and the exact node release. Complete describes a finished document; full validation of the new rules begins only after a separate soft-fork activation, if one occurs. [2]
For the clearest picture, read this entry together with Consensus Rules, Soft Fork, Timewarp Attack, Proof of Work, Bitcoin Core, Transaction. The reverse links also lead from Timewarp Attack.
01Is BIP 54 active on Bitcoin mainnet?+
No. The specification is Complete and an implementation without mainnet activation exists, but the consensus restrictions require a separate activation process.
02What exactly does Consensus Cleanup change?+
It tightens timestamps at difficulty-period boundaries, caps legacy sigops per transaction, forbids exactly 64-byte transactions without witness data, and enforces uniqueness of future coinbase transactions.