Bitcoin infrastructure firm Blockstream has launched “Simplicity,” a purpose-built smart-contract language, on the mainnet of its Liquid sidechain. The release, made on 31 July after eight years of development, is the first production deployment of a non-Bitcoin-Script framework intended to expand Bitcoin’s programmability. Simplicity is designed to be more expressive than Bitcoin Script yet safer than general-purpose languages such as Ethereum’s Solidity. By excluding recursion, unbounded loops and mutable global state, the language allows every execution path and fee cost to be proven in advance, a feature Blockstream says will reduce re-entrancy bugs and make the contracts attractive to institutional users. Because Simplicity runs on Liquid—a federated, layer-2 network operated by the Liquid Federation—the launch gives developers a faster and more private environment for applications such as vaults, delegated controls and cash-settled derivatives. Analysts note, however, that the sidechain’s governance model could introduce censorship or centralization risks not present on Bitcoin’s base layer. Blockstream Head of Research Andrew Poelstra said the move positions Bitcoin as a “programmable platform for financial infrastructure.” On 4 August, Tel Aviv-based StarkWare said it is collaborating with Blockstream to combine Simplicity with its STARK zero-knowledge proofs in an effort to explore new scaling techniques for Bitcoin.