What happened
On 9 August 2026 the changelog of BIP-110, in Bitcoin's proposal repository, gained a single line: "Mark as Closed, following a chain split with stalled mining." The status change was merged the next day in pull request #2245, where the editor who opened it recorded that the proposal had been released on mainnet by the Bitcoin Knots implementation, entered its mandatory signalling period on 8 August, and then "split to a new chain and stalled."
BIP-110, titled "Reduced Data Temporary Softfork", proposed to cap the size of arbitrary data fields in Bitcoin transactions for roughly a year.
What it changes
Nothing about Bitcoin's rules. What it changes is what we can point at when someone asks why miner support matters for a soft fork, because the proposal's own deployment section sets out the trap precisely.
BIP-110 used mandatory signalling: version bit 4, a threshold of 1,109 blocks out of every 2,016 (55%), and a window running from block 961,632 to block 963,647. Mandatory means what it says. From block 961,632, a node running BIP-110 would reject any block that did not set the bit, not ignore it, reject it as invalid.
That is a rule about validity, so the moment a block arrived without the bit, nodes running BIP-110 and nodes running everything else no longer agreed on which chain existed. The enforcing nodes followed a different one.
The second half is arithmetic. Difficulty in Bitcoin is not a rate that tracks hashrate continuously; it is a fixed number that only retargets every 2,016 blocks. A chain that splits away inherits the whole network's difficulty and keeps whatever share of the hashrate came with it, and it cannot adjust until it has mined 2,016 blocks at that inherited setting. The correction is measured in blocks, not in days, which is why a minority chain does not simply run slowly - it can stop being practical to mine at all before it ever reaches its first retarget.
What it does not change
Bitcoin's consensus rules are exactly what they were on 7 August. Anyone who was not running BIP-110 software saw an ordinary week.
Nor does Closed mean refuted. BIP-3, the process document, defines the status as a proposal "of historical interest only, and is not being actively worked on, promoted or in active use", and adds that "BIPs do not get deleted, they are retained even after being updated to Closed." The editors in the pull request discussed whether to route it through Deployed first and concluded that the activation criteria had never been met on the network. The document stays, the question it was asking stays open, and the argument about arbitrary data in transactions is unchanged by any of this.
Context
BIP-110 was not a quick idea. Its own changelog runs from an initial draft on 24 October 2025, through a deployment-parameter change, a UTXO grandfathering clause and a rewrite against the current process document, to Complete on 25 June 2026 - about ten months before the window opened.
If the mechanics above are new, the two pieces underneath them are what a node actually does and how mining and difficulty fit together. The split is only surprising if you think of nodes as passive followers of miners; it makes immediate sense once you see that a node's job is to reject blocks it considers invalid, whoever mined them.