Why Did Bitcoin Split At Block 961,632?
Bitcoin entered a contentious test of its consensus rules on Saturday after nodes enforcing BIP-110 began rejecting blocks that did not signal support for the proposal, creating a minority branch with only a small share of the network’s mining power.
BIP-110 entered its mandatory-signaling phase at block 961,632. From that point, participating nodes required new blocks to set version bit 4, while ordinary Bitcoin nodes continued accepting both signaling and non-signaling blocks.
The split occurred almost immediately. AntPool mined a block at height 961,632 without the required signal, which the dominant Bitcoin network accepted but BIP-110 nodes rejected. An alternative signaling block was later produced through Ocean by Roughnecks, giving the enforcing nodes a separate chain to follow.
The problem for BIP-110 supporters is mining power. Only 51 of the preceding 2,016 blocks signaled support for the proposal, equal to 2.53%, far below the 55% threshold needed for activation without a split.
The difference quickly became visible in block production. While Bitcoin’s main chain continued operating at its normal pace, the BIP-110 branch had produced only two additional blocks and was already seven blocks behind at one stage on Saturday.
What Does BIP-110 Change?
BIP-110, written by pseudonymous developer Dathon Ohm, proposes temporary consensus restrictions intended to reduce the amount of non-financial data stored on Bitcoin. The rules would remain in place for 52,416 blocks, roughly one year.
The proposal would limit most new output scripts to 34 bytes, cap OP_RETURN outputs at 83 bytes, restrict certain data pushes and witness elements to 256 bytes and temporarily restrict several Taproot features. Unspent transaction outputs created before activation would be exempt.
Supporters argue that inscriptions and other forms of permanent non-monetary data increase storage and bandwidth costs for node operators and compete with financial transactions for limited block space.
Critics argue that miners should remain free to include any valid transaction that pays the required fee and that consensus rules should not attempt to determine which uses of Bitcoin are acceptable. The dispute intensified after Bitcoin Core changed its default OP_RETURN policy in its October 2025 v30 release, effectively removing the longstanding 83-byte relay limit.
Strategy Executive Chairman Michael Saylor opposed BIP-110 in July, writing: “Bitcoin does not need guardians of purity. It needs guardians of neutrality.” Blockstream CEO Adam Back has also criticized the proposal over the risk of dividing the network.
Investor Takeaway
The immediate issue is not whether BIP-110 exists as a minority fork, but whether it can attract enough hash power, exchanges, wallets and other infrastructure to become economically relevant. With miner signaling near 2.5%, the dominant Bitcoin chain currently has an overwhelming advantage.
Can A User-Activated Fork Succeed Without Miners?
BIP-110 supporters are pursuing the proposal as a user-activated soft fork, or UASF. Under that model, node operators attempt to impose new rules by refusing blocks from miners that do not comply, potentially forcing miners to follow users rather than waiting for miners to approve the change first.
Supporters point to the 2017 SegWit dispute and BIP-148 as evidence that node operators can influence activation. The current situation is different, however, because BIP-110 has entered its enforcement period with exceptionally low miner signaling.
Without additional hash power, blocks on the minority branch could arrive very slowly. In an extreme case, the chain could stop advancing altogether until a participating miner finds another valid block.
The specification sets blocks 961,632 through 963,647 as the mandatory-signaling period. Block 963,648 begins the locked-in state, while the new transaction restrictions are scheduled to take effect at block 965,664 if the BIP-110 branch reaches those milestones.
Developers have also discussed a more aggressive contingency. Bitcoin developer Chris Guida recently rebased preliminary code for a proof-of-work change originally written by Bitcoin Knots maintainer Luke Dashjr, describing it as a possible fallback if miners reject BIP-110. No activation date has been set.
What Would Make The Minority Chain Matter?
Mining support alone will not determine whether the BIP-110 branch develops economic value. Exchanges, custodians, wallet providers, payment companies and institutional holders would also need to decide which chain they recognize as Bitcoin.
The proposal does not automatically create a separately traded asset. A lasting market split would require infrastructure providers to recognize balances on both chains and potentially assign distinct tickers, deposits, withdrawals and prices.
For now, that appears unlikely. The main chain has nearly all of the hash power and institutional infrastructure, while the BIP-110 branch is advancing slowly. Bitcoin’s market price also showed no obvious reaction immediately after the fork emerged.
The more important test may be political rather than financial. BIP-110 is forcing Bitcoin users, miners and developers to confront who ultimately decides how block space can be used. Unless miner support rises sharply, however, the first phase of that contest is being decided by hash power: the dominant chain is moving ahead while the enforcing minority struggles to keep pace.