Why Bitcoin’s Next Soft Fork Could Feel Like a Practice Run

Four flaws in Bitcoin’s consensus rules that have lingered for years.

Issues like quantum resistance may command attention, but a practical cleanup is what many experts think Bitcoin’s next soft fork is likely to address, spanning fixes for vulnerabilities in the network’s difficulty adjustment mechanism to denial-of-service vectors among miners.

Proposed in 2019 and known as the Great Consensus Cleanup (BIP-54), the upgrade seeks to address the “cruft” in Bitcoin’s consensus design through changes that have historically been sidelined, as described by long-time Bitcoin developer and BIP-54 co-author Matt Corallo.

“There’s a laundry list of things we know of that we really need to clean up,” he said during a recent appearance on MARA Foundation TV. “All of these issues are real concerns that could impact Bitcoin negatively, but they’re not like, ‘Oh, the sky is falling.’”

Although a formal timeline for the BIP’s undertaking hasn’t been established, Corallo thinks there’s an 80% chance that the Great Consensus Cleanup is up next for the network. During his talk with Head of MARA Foundation Isabel Foxen Duke, he also called it a practical exercise for Bitcoin developers who haven’t yet been through a soft fork.

At its core, Corallo said BIP-54 “fixes some stuff that everyone agrees are problems,” while targeting four specific vulnerabilities:

• Poison blocks: If a miner wanted to gain a temporary advantage over competitors, they could mine a specially crafted block that exploits performance bottlenecks, intentionally slowing down node validation for everyone else.

• Time warp bugs: A loophole in Bitcoin’s two-week difficulty adjustment window allows miners controlling a majority of hashrate to manipulate block timestamps, artificially accelerating the rate at which new blocks are issued.

• Merkle malleability: Because a 64-byte transaction happens to be the exact same data size as an internal Merkle tree node, an attacker can theoretically forge proofs to trick light clients into accepting fake transactions.
• Duplicate coinbase transactions: Historical design quirks that allowed duplicate transaction IDs will resurface at future block heights, creating a vulnerability that could overwrite existing coins or disrupt ledger accounting.

Still, not everyone views a maintenance-focused soft fork as a major win. On X, Paul Sztorc, co-founder and CEO of LayerTwo Labs, called BIP-54’s potential activation “kind of depressing, since it is a janitorial maintenance fork that doesn’t do anything.”

Surveying developers at TABconf in Atlanta, Sztorc noted that Bitcoin’s “best and brightest” predominantly expect the Great Consensus Cleanup to be Bitcoin’s next soft fork anyway, with the earliest estimate in September 2027, and most pointing to 2028 or later.

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Following the activation of Taproot in 2021, Bitcoin’s community has faced years of gridlock surrounding protocol changes. This friction is frequently framed around “ossification,” with broader protocol changes like OP_CAT (BIP-347) and OP_CHECKTEMPLATEVERIFY (BIP-119) struggling to reach ecosystem-wide consensus.

According to Corallo, soft forks have always involved overcoming technical hurdles. But more recently, he’s observed political and social friction that’s become just as relevant.

The Bitcoin community spent months debating how Taproot should be activated, with arguments pitting miner-signaling thresholds against mandatory user flag days. Corallo argues that BIP-54 can establish a deployment playbook for future soft forks.

“In every recent soft fork, there’s also been a bunch of drama about activation mechanisms,” he said. “So hopefully we could do a soft fork to go through that drama, and then copy and paste and reuse it and head off some of that drama [for future soft forks].”

In that sense, BIP-54 is just as much about proving Bitcoin can still agree on upgrades at the social layer as it is about actual code cleanup.

André Beganski is a Senior Content Manager at MARA Foundation, producing content on topics including the intersection of quantum computing and cryptography. He has previously worked for Decrypt.