Bitcoin developers want to remove a wallet privacy leak. The fix only works if every wallet picks the same value.
The BIP 125 opt-in flag tells chain-analysis tools exactly which wallet software sent a transaction. Removing it without ecosystem-wide coordination trades one fingerprint for many new ones.
CryptoVibe Desk · bitcoin · privacy · wallets
- →Bitcoin developers are proposing to drop explicit RBF signaling from wallets because full-RBF made the BIP 125 opt-in flag redundant, but it still leaves a fingerprint visible on-chain.
- →The sequence field is mandatory, so wallets must pick a value; if the whole ecosystem converges on MAX-2, transactions become indistinguishable, but uncoordinated removal creates a new set of fingerprints instead.
- →Watch for whether Bitcoin Core, Sparrow Wallet, and Electrum all ship MAX-2 as their sequence default in the same release cycle before the end of 2026, which is the only condition that makes the privacy argument hold.
- RBF (replace-by-fee) → A way to replace an unconfirmed Bitcoin transaction with a new version that pays a higher fee, so miners are more likely to include it in the next block.
- BIP 125 → A Bitcoin standard that let wallets signal willingness to have a transaction replaced by a higher-fee version; now redundant because all transactions are treated as replaceable under full-RBF.
- Full-RBF → A network policy where Bitcoin nodes accept any replacement transaction with a higher fee, regardless of whether the original transaction used the BIP 125 opt-in signal.
- Sequence number / MAX-2 → A technical field every Bitcoin transaction must include; when all wallets use the same value called MAX-2, their transactions look identical to chain-analysis tools, which protects privacy.
The BIP 125 sequence flag was supposed to tell miners a transaction is replaceable. Full-RBF made that signal meaningless. Every transaction is replaceable now regardless of what the flag says. But the flag is still being set, and chain-analysis tools are still reading it.
Developer rkrux posted to the Bitcoin developer mailing list this week proposing wallets drop the opt-in signal entirely. The logic is clean: if the network treats every transaction as replaceable anyway, the flag adds nothing except a fingerprint. Wallets that set it and wallets that don't emit distinguishably different sequence numbers. That tells chain-analysis tools which software created the transaction.
And that's the catch. The sequence field is mandatory. Wallets cannot simply remove it. They have to pick a value, and that value is visible on-chain.
Developer Murch clarified the privacy-preserving path: converge on MAX-2. That's the sequence number already used by roughly 75% of Bitcoin transactions, per CoinDesk. If every wallet picks the same default, transactions become homogeneous and harder to attribute. If wallets diverge, the diversity of values creates a new fingerprinting surface.
This is a coordination problem, not a technical one. The fix is known. The question is whether Sparrow, Electrum, Bitcoin Core, and every hardware signer ships the same default in the same release cycle. If they do it at different times, the deployment window itself becomes a new fingerprinting signal.
At the contract level, changing a sequence default is subtle in ways the announcement won't say. It changes how fee-bumping behavior is inferred by external tools. The fingerprint you remove and the fingerprint you create depend entirely on what the rest of the ecosystem ships alongside you.
No code has merged. This is still a mailing list discussion, with a PR open against Bitcoin Core wallet that wasn't linked in the primary report. If you're building wallet software that sets BIP 125 signals today, this is worth watching now, not after the PR lands.
Read the PR diff, not the thread.
Bitcoin Core keeping this on the mailing list while wallets ship their own defaults is the actual privacy risk, not the RBF signal removal. The engineering answer is settled. The organizational gap is where fingerprints multiply.
Whether Sparrow Wallet, Electrum, and Bitcoin Core all ship MAX-2 as their sequence default within the same release cycle before the end of 2026, which is the minimum condition for the homogeneity argument to hold.
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