BIP 110 and the Cost of Policing Bitcoin's Block Space

Originally published by InvisibleHill Research . This cross-post preserves the original research cut-off and source list. Research cut-off: July 30, 2026. Miner signaling is a live metric and may have changed after publication. BIP 110 begins with a problem that many Bitcoin users can recognize. A miner can collect a one-time fee for including an image, token payload, or other arbitrary data, while thousands of node operators absorb the cost of downloading, validating, and sometimes storing it. The proposal's authors see that mismatch as a subsidy for data storage and a threat to Bitcoin's use as money. Their answer is a temporary soft fork. For about one year, BIP 110 would make several currently valid transaction structures invalid under consensus rules. It would cap OP_RETURN outputs at 83 bytes, limit many data pushes and witness items to 256 bytes, restrict large output scripts and Taproot control blocks, and disable several Taproot upgrade paths and script features that can carry data. Adam Back agrees with the premise more than his opposition sometimes suggests. He has said that Bitcoin is about money and that spam has no place in its timechain. He also designed Hashcash to make spam costly. His objection is to the remedy. In Back's view, an annoyance that fits inside Bitcoin's existing block limit does not justify a contentious consensus change, especially one that can be bypassed, can interfere with legitimate scripts, and has not earned technical or economic agreement. That distinction is the center of the debate. BIP 110 asks whether Bitcoin should discourage an unwanted use through local policy and fees, or declare some forms of that use invalid for everyone. Back's case is stronger on this question. The proposal identifies a real externality, but it offers an asymmetric bargain: incomplete filtering in exchange for a new consensus precedent, a more complicated upgrade path, and a material risk of a minority chain. A policy dispute became a consensus pro