Bitcoin Optech Newsletter #263: Proposed changes to Bitcoin Core default relay policy

It’s too bad you can’t link to subsections of the newsletter… See the newsletter for details, and it also includes links I was too lazy to add here.

Full RBF by default: the first thread and pull request proposes making full RBF the default setting in a future version of Bitcoin Core. By default, Bitcoin Core will currently only relay and accept into its mempool replacements of unconfirmed transactions if the transaction being replaced contains the BIP125 signal indicating opt-in replaceability (and if both the original transaction and the replacement transaction follow some other rules), called opt-in RBF. A configuration option, -mempoolfullrbf, allows node operators to instead choose to accept replacements of any unconfirmed transaction even if it didn’t contain the BIP125 signal, called full RBF (see Newsletter #208). Peter Todd’s proposal would make full RBF the default but allow node operators to change their settings to choose opt-in RBF instead.

Peter Todd argues that the change is warranted because (according to his measurements, which have been called into doubt), a significant percentage of mining hash rate is apparently following full RBF rules and there are enough relay nodes that have enabled full RBF to allow non-signaled replacements to reach those miners. He also says he is unaware of any active businesses that currently accept unconfirmed onchain transactions as final payment.