Stellar Protocol 21 activated on Mainnet on June 18, 2024, introducing five Core Advancement Proposals (CAPs) that add passkey signing support, improve state archival, and reduce smart contract transaction costs. Developers and operators must upgrade their Stellar-related software and re-upload existing Wasms to benefit from the new cost model.
Following a successful validator vote on June 18, 2024, Stellar's public network upgraded to Protocol 21, activating five new Core Advancement Proposals (CAPs). The upgrade introduces passkey signing support (CAP-0051), improved state archival (CAP-0053), a refined VM instantiation cost model (CAP-0054), streamlined linking (CAP-0055), and intra-transaction module caching (CAP-0056). Developers must upgrade all Stellar-related software including Stellar Core v21.0.0+, Horizon, Soroban RPC, and SDKs across multiple languages. A critical requirement for validators is setting the new DEPRECATED_SQL_LEDGER_STATE configuration flag when deploying Stellar Core 21.0. Existing smart contracts uploaded in Protocol 20 should be re-uploaded to take advantage of the tightened cost model introduced by CAP-0054.