Protocol 28 (Adapter) upgrades the Stellar network with three builder-focused improvements: faster consensus under load via CAP-83, atomic contract fleet upgrades through shared code references (CAP-85), and safer contract data migration with sparse host functions (CAP-86). Testnet upgrade August 27, mainnet vote September 16.
Stellar's Protocol 28 (Adapter) ships three improvements focused on the builder ecosystem. CAP-83 accelerates consensus by allowing validators to vote before transaction sets fully arrive and to explicitly drop late or invalid sets instead of stalling, improving throughput and resilience at scale. CAP-85 enables atomic contract fleet upgrades: contracts can point to a shared, updatable code reference owned by another contract, implementing the beacon proxy pattern. A single update to that shared reference atomically upgrades every dependent contract, eliminating windows of inconsistent state and the risk of partial upgrades in large fleets. CAP-86 introduces sparse host functions that gracefully handle missing or extra fields in contract data, enabling safe schema evolution and live contract data migration without breaking. The upgrade follows a fixed schedule: stable releases August 13, testnet upgrade August 27, mainnet vote September 16. Validators, infrastructure operators, SDK users, wallets, exchanges, issuers, and protocols each have preparation steps in the Protocol 28 Upgrade Guide.
