The Bitcoin Improvement Proposal known as BIP-110 stalled over the weekend after nodes supporting the proposal broke away from Bitcoin's main network, producing the chain split that critics had been warning about — a minor one that has barely advanced.

The split occurred on Saturday at block 961,632, when the proposal entered its mandatory signaling window. Nodes running BIP-110-enforcing software began rejecting any block that did not signal support via version bit 4. When the first block at that height arrived without the required signal, those nodes rejected it and forked onto a separate chain.

Since then, the fork has gone almost nowhere.

A pseudonymous mining group called Roughnecks produced both BIP-110 blocks — at heights 961,632 and 961,633 — using Ocean's DATUM protocol, then ceased mining. By Sunday afternoon, the enforcing branch remained stuck at block 961,633, while Bitcoin's dominant chain had advanced to block 961,744 — a gap of 111 blocks and approximately 17 hours without a single new block on the fork.

Network support for the proposal fell far short of what was required. Only 51 of the 2,016 blocks in the preceding difficulty period signaled for the proposal — approximately 2.53% — well below the 55% threshold needed for voluntary lock-in. Since the mandatory window opened, none of the first 113 blocks on the dominant chain have signaled. By comparison, successful Bitcoin soft forks such as SegWit and Taproot achieved activation only after securing broad backing across miners, developers, and major economic nodes over extended coordination periods.

Bitcoin's difficulty adjustment mechanism further compounds the fork's challenges. The fork inherited the main chain's difficulty level but commands only a negligible share of total hashpower, and mining cannot become easier until a full 2,016-block difficulty period is completed. Estimates for how long that would take range from under a year to decades, depending on the assumed hashrate.

BIP-110, formally titled the Reduced Data Temporary Softfork, would have capped arbitrary data embedded in transactions for approximately one year, specifically targeting Ordinals inscriptions and oversized OP_RETURN payloads. The proposal emerged from an ongoing debate within the Bitcoin community over the use of block space for non-financial data, which intensified after the launch of the Ordinals protocol in early 2023 enabled NFT-like inscriptions directly on the Bitcoin blockchain.

Michael Saylor and Blockstream's Adam Back both publicly opposed the proposal. Their objections focused less on the stated goal than on the activation method, which they argued was designed to produce precisely this kind of outcome. Saylor wrote on Sunday that Bitcoin had functioned as intended, with 99.85% of hashpower remaining on the main chain.

Mining company Ocean, whose team supported the proposal, notified clients that some miners using Ocean's Stratum templates may have believed they were mining on Bitcoin while their hashrate was inadvertently directed to the new BIP-110 chain. Ocean stated it would reimburse affected miners with the rewards they would have earned on the non-BIP-110 chain during that period.

This article first appeared on Bitcoin Magazine and was written by Mathew Di Salvo.