Bitcoin split into two active chains on Saturday after nodes running BIP-110 software began rejecting blocks that did not signal support for the proposal, creating a minority branch that quickly fell behind the network’s established chain.
The break started at block 961,632, when AntPool mined a block accepted by the broader Bitcoin network but rejected by BIP-110 nodes. Those nodes instead followed a competing block at the same height, attributed by Mempool Guide to Roughnecks and mined through Ocean.
The result is a live consensus divide over whether Bitcoin should impose stricter limits on non-financial transaction data, including Ordinals inscriptions. BIP-110 supporters are enforcing the limits before the proposal has obtained the miner support threshold specified for a non-disruptive activation.
By 6:00 p.m. ET, the main Bitcoin chain had reached block 961,640, while the BIP-110 branch had advanced only to block 961,633 after producing two blocks beyond the split point. The alternative chain was seven blocks behind, reflecting its much smaller share of active mining power.
Both versions of block 961,632 extended block 961,631, but they contained different transaction sets. Once BIP-110 nodes rejected AntPool’s block, they also rejected every subsequent block built on it. They cannot automatically return to the main chain unless their operators alter the software configuration or stop enforcing BIP-110’s rules.
bip-110 imposes data restrictions for one year
BIP-110 would temporarily tighten Bitcoin’s consensus rules around data storage in transactions. Its design targets transaction structures commonly used to embed files, text, images and other non-payment material on the blockchain.
The proposal caps certain data fields at 256 bytes, retains an 83-byte limit for OP_RETURN outputs, and restricts some Taproot functions. OP_RETURN is a Bitcoin transaction feature that can carry arbitrary data. Taproot, activated in 2021, introduced new ways to structure transactions and has become a common component in inscription-related activity.
Under the BIP-110 specification, the restricted rules would apply for 52,416 blocks, described as roughly one year. The rules would start at block 965,664, but only if the BIP-110 chain reaches block 963,648 first.
That schedule creates an unusual activation path. The proposal allowed for activation through miner signaling if at least 55% of blocks in a 2,016-block period supported it, a threshold equal to 1,109 blocks. The signaling route was intended to avoid a persistent chain split by ensuring a large portion of hash power had adopted the same rules.
Only 51 of the 2,016 blocks mined in the two weeks before the fork signaled support for BIP-110, according to the supplied signaling data. That equates to 2.53%, far below the proposal’s 55% threshold.
None of the first nine blocks produced on the main chain after the split carried a BIP-110 signal. The proposal’s enforcement phase therefore began without evidence that a meaningful share of the network’s miners had adopted the software.
a different route from Taproot’s activation
Bitcoin has experienced contentious technical debates before, but BIP-110’s rollout differs sharply from the activation of Taproot. Taproot locked in after broad miner signaling and became active at block 709,632 in November 2021 without leaving a durable minority chain behind.
BIP-110 nodes have instead created a chain that validates a different set of blocks from the rest of the network. The branch began with a one-block divergence and expanded into a seven-block gap within hours as the established chain continued to receive the overwhelming majority of mining work.
The split does not create a new Bitcoin asset under BIP-110’s design. Users holding bitcoin on the chain before the fork do not automatically receive a separately traded token simply because some nodes are enforcing different rules.
Its immediate effect is operational rather than economic: software, services and miners must decide which chain they recognize as Bitcoin’s valid history. A minority chain can remain active as long as participants continue mining it and running nodes that accept its blocks, though the growing block gap makes it harder for that branch to compete for the network’s proof-of-work security.
the dispute reaches beyond relay policy
BIP-110 also reopens a debate triggered by Bitcoin Core’s handling of OP_RETURN transactions. In Bitcoin Core v30, released in October 2025, the software removed its longstanding default 83-byte OP_RETURN relay limit.
Relay policy governs which transactions nodes generally forward across the peer-to-peer network and toward miners. It does not itself change Bitcoin’s consensus rules, meaning nodes could still choose their own transaction acceptance policies while remaining on the same blockchain.
BIP-110 goes further by placing restrictions in consensus validation. A transaction that violates the new limits would be invalid for nodes enforcing the proposal, even if miners on the main chain include it in a block. That difference explains why the disagreement has produced competing histories rather than simply different transaction relay preferences.
Supporters of tighter limits argue that Bitcoin should prioritize monetary transfers and resist uses that consume block space for durable data storage. Critics have argued that forcing new consensus limits without broad agreement risks fragmenting the network and gives a minority of participants disproportionate influence over which valid transactions users may make.
Bitcoin traded near $65,000 at the time described in the supplied material, with no specific market move linked to the fork. The more immediate measure of BIP-110’s viability is likely to be block production: its branch needs sustained mining support to close the gap or progress toward its specified activation height while the main chain continues to extend a competing record.
Learn how Bitcoin mining mechanics influence forks, chain splits, and consensus during upgrades like BIP-110.
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