July 25: BitcoinOS, a network of Bitcoin-based rollup chains, has verified the first-ever zero-knowledge (ZK) proof on Bitcoin’s mainchain. ZK cryptography is looked to as a key technology for scaling blockchain throughput and usefulness, but the tech is complicated and computationally intense – meaning it was unclear if or when it would make its way to the comparatively bare-bones Bitcoin network. According to the BitcoinOS team, “This is the first permissionless upgrade of the Bitcoin system and the first time Bitcoin has been upgraded without a soft fork.” Bitcoin can now be “infinitely upgradable,” the team told CoinDesk, “while requiring no changes to the consensus code.” BitcoinOS aims to be the “ultimate implementation of a Bitcoin rollup system,” eventually serving as a bridge connecting any number of rollups – quick and cheap layer-2 blockchains that are secured by the Bitcoin blockchain and ZK proofs.