BIP-110, and What a Failed Fork Teaches Us
From The Weekly BOLT ·
On Saturday evening, at block height 961,632, Bitcoin experienced its first chain split in years. A contested proposal called BIP-110 entered a phase in which nodes running its software began rejecting any block that didn't signal support for it — and when the very first block at that height arrived without the required signal, those nodes rejected it and split off onto their own chain. It sounds dramatic. In practice, the minority chain produced two blocks, stalled, and fell nearly a hundred blocks behind while the main Bitcoin network carried on without so much as a hiccup. This week's Bite unpacks what BIP-110 actually is, what happened, and why this apparently minor episode is one of the most instructive things Bitcoin has done in years.
The Basics: BIP-110, formally titled the "Reduced Data Temporary Softfork" and authored under the pseudonym Dathon Ohm, is a proposal to temporarily limit how much arbitrary, non-financial data a Bitcoin transaction can carry. It targets the practice — begun with the "inscription" techniques of 2022 — of embedding images, tokens, and other data into the blockchain, the machinery behind Ordinals, BRC-20 tokens, and Runes. The proposal contains seven consensus rules that cap most new output scripts at 34 bytes, restrict OP_RETURN fields to 83 bytes, and limit certain data pushes to 256 bytes. Critically, the rules were designed to expire on their own after about a year. Supporters argue it defends Bitcoin's purpose as sound, permissionless money and protects node operators from bloated blockchain storage costs. Critics call it censorship with real chain-split risk, and warn about technical side effects on more complex Taproot scripts.
Why It Matters — How Bitcoin Actually Changes: Bitcoin has no CEO, no board, and no foundation that can decide the rules. Changes happen only when three overlapping groups converge: miners, who choose which valid chain to extend; nodes, which independently validate and enforce the rules; and users, who decide which chain's coins they actually recognize and accept as payment. A soft fork tightens the rules so that old nodes still accept new blocks — backward compatible, and historically requiring roughly 95% miner signaling to activate safely. A hard fork loosens or changes the rules incompatibly and creates a permanent second chain unless everyone upgrades. BIP-110 used an unusual mechanism: a 55% miner-signaling threshold, far below the traditional 95%, with a "mandatory signaling" fallback if voluntary support fell short. That fallback is what fired this weekend — a user-activated approach in which a minority of nodes attempt to force the rest of the network's hand by refusing to accept non-compliant blocks.
What Actually Happened: Miner support never materialized. In the final two-week window before the deadline, just 51 of 2,016 blocks signaled for BIP-110 — 2.53%, against the 55% needed, with nearly all of it coming from a single mining pool. At roughly 19:35 UTC on Saturday, the network hit block 961,632, and BIP-110-enforcing nodes began rejecting non-signaling blocks. A large pool mined the block on the main chain; a small operation mined a competing, compliant version; and the split was logged by fork-monitoring sites within minutes. The enforcing branch then managed exactly two blocks before grinding to a halt at 961,633 — with only a sliver of hashpower, blocks come agonizingly slowly. By Sunday the main chain had raced roughly a hundred blocks ahead, and no BIP-110 signaling appeared among the first hundred blocks of the new difficulty period. Prominent voices including Michael Saylor and Blockstream's Adam Back had opposed the effort, with Saylor arguing that Bitcoin needs neutrality rather than enforced "monetary purity," and noting after the split that BIP-110 would simply stall or fork into irrelevance while Bitcoin continued normally. One important practical note for holders: BIP-110 included no replay protection, because it was never designed to create a split — so transactions could theoretically be valid on both chains. If you hold your own keys and simply did nothing this weekend, you were unaffected.
The Long-Term Lesson: Here is why we think this matters far more than the modest headlines suggest. Bitcoin's most important property is not its speed, its fees, or its programmability — it is the extraordinary difficulty of changing its rules. That difficulty is what makes a 21-million supply cap credible. This weekend, a determined, technically sophisticated group with real conviction attempted to change Bitcoin's consensus rules with roughly 2.5% support, and the network simply routed around them. No emergency meeting, no committee vote, no authority stepping in. The economic majority kept mining, kept transacting, and the minority chain withered on its own. Note also the context: Bitcoin's last consensus change was Taproot, in November 2021, making this the longest stretch of rule stability in its history. In an era when every other monetary system's rules can be rewritten overnight by a handful of officials — and when, as we've documented all year, they are being rewritten through deficits, interventions, and eventual debasement — Bitcoin just demonstrated on a live network that its rules cannot be changed by anything short of overwhelming consensus. That's not a bug that produced an awkward weekend. That's the entire product, working exactly as designed, in public. One further note for the calendar: a separate hard fork called eCash is targeted at block 964,000, around August 21, which would split off and airdrop a new coin to holders. Expect noise; expect Bitcoin to keep producing blocks every ten minutes regardless.