Bitcoin Core v30 Sparks Debate Over OP_RETURN Cap Removal

Bitcoin Core developer Antoine Poinsot’s recent pull request to remove the 80-byte OP_RETURN relay cap has sparked a heated debate within the Bitcoin community. This change, which is set to be included in the upcoming v30 release of Bitcoin Core, has led to a significant divide among node operators and developers.

The controversy escalated when a contributor posted a public bash script designed to auto-ban nodes running Bitcoin Knots, a policy-opposed implementation. This script, if widely adopted, could isolate nearly 3,000 publicly reachable nodes, significantly undermining Bitcoin’s decentralization. The script, published on GitHub, enacts a year-long ban on all /Satoshi:Knots/ user agents, effectively cutting off a substantial portion of the network.

The dispute centers on relay policy rather than consensus rules, which means the operational split could occur without a hard fork. The Knots implementation has gained traction since the Core team merged Poinsot’s OP_RETURN policy change on May 6. Its share of reachable nodes has doubled over several weeks, coinciding with vocal criticism from its lead maintainer, Luke Dashjr, who described the removal of the cap as “utter insanity.”

While OP_RETURN is not consensus-critical, node-level policy decisions shape transaction propagation and mempool filtering. These decisions influence what miners include in blocks and which data-bearing transactions reach the network. The origins of this dispute date back to 2014 when Bitcoin Core first enforced an 80-byte OP_RETURN limit. Initially used for data inscriptions, the OP_RETURN field became a spam vector during peak usage periods. Recent innovations like Ordinals and BRC-20 tokens have utilized similar mechanics to push high-fee, high-volume transactions onto the chain.

Core v30’s scheduled October release will remove the cap entirely, allowing transaction creators to include larger OP_RETURN payloads provided they pay the requisite fees. Opponents view this shift as undermining Bitcoin’s role as a lean, monetary settlement layer. Samson Mow, CEO of JAN3, urged users to “refuse to upgrade and stay on 29.0 or run Knots,” framing the issue as one of protecting network integrity. Others, like Peter Todd, see the removal as a necessary simplification that defers to market conditions and fee incentives.

Because the OP_RETURN cap is enforced at the policy level, node operators can adopt or reject the change individually. This dynamic has elevated the role of miners and relay infrastructure operators, who ultimately decide which transactions make it into candidate blocks. If a critical mass of top pools sides with Knots, blocks filled with larger OP_RETURN data may fail to propagate efficiently, creating a de facto veto. Conversely, if Core’s defaults dominate, alternative policies could become siloed and economically irrelevant.

Key participants began trading personal accusations as the dispute migrated from GitHub to public channels. Poinsot accused critics of “intentionally misleading” the public and “making s*** up,” amid growing hostilities over technical matters, governance, and communication norms. The broader implications may extend to Bitcoin’s ability to accommodate divergent policy views without splintering its operational cohesion.

Unlike the 2017 block size debates, the OP_RETURN split does not require incompatible consensus rules. Still, the threat of a partitioned network looms, especially if coordinated peer bans become widespread. While block propagation across the two camps may remain functional, transaction relay pathways could fracture, impacting fee markets, data services, and blockchain analytics.

Bitcoin Core’s v30 client is now scheduled to freeze on August 20, with a branch-off planned for around September 6 and a final release tag targeted for October 3. No major mining pools have issued statements regarding relay policy settings, leaving open whether v30’s changes will propagate by default or face silent resistance. Since May, the number of Bitcoin Knots nodes has continued to climb, reaching 2,938 as of June 24, the highest on record and accounting for just over 13 percent of reachable peers. The original ban script remains live, and at least one new tool, btc-magic-guard, has emerged offering iptables-based filtering to isolate nodes running policy-divergent clients.

Meanwhile, a follow-up proposal to allow multiple OP_RETURN outputs per transaction was recently withdrawn after pushback, suggesting Core maintainers are unlikely to revisit or narrow the merged policy before v30 ships. For now, the network remains unified under shared consensus rules, but the unresolved divergence in relay behavior, peer connectivity, and node policy has made soft partitioning a tangible scenario ahead of the October release.