Stellar Protocol 28, called Adapter, will upgrade testnet August 27 and mainnet September 16, 2026. Developers must update SDKs, validators must install Stellar Core and enable NTP synchronization, and infrastructure operators must deploy new releases. CAP-83, CAP-85, and CAP-86 introduce empty transaction set consensus, external smart contract executables, and efficient contract data structures.
Stellar Protocol 28 (Adapter) will upgrade the network's testnet on August 27 and proceed to a mainnet vote on September 16, 2026. Preparation requirements vary by role: SDK users must upgrade by each date; validators must install Stellar Core and enable NTP clock synchronization before September 9; infrastructure operators (Horizon, RPC, Galexie) must pull Protocol 28 releases by August 21. The upgrade introduces CAP-83 (empty transaction set consensus), CAP-85 (externally managed contract executables), and CAP-86 (sparse maps for contract data). Most integrations require only SDK version bumps. Soroban teams can opt into CAP-85 and CAP-86 features when rebuilding against the updated SDK. Raw ledger data consumers should handle the new empty transaction set type. The official guide covers breaking changes, release links, and step-by-step preparation instructions for each ecosystem participant.
