Stellar Protocol 28 upgrade targets September 16 mainnet activation

Protocol 28, Stellar's Adapter upgrade, heads to a Sept. 16 mainnet vote with three changes targeting Soroban smart contracts and network consensus performance.

"Adapter is, above all, a release for builders," the Stellar Development Foundation said in its announcement. "Two of its three changes are aimed squarely at making Soroban smart contracts easier to build, upgrade, and scale."

The upgrade bundles three Core Advancement Proposals. CAP-83 lets validators begin voting before a full transaction set arrives, reducing stalls under load. CAP-85 introduces an externally managed executable, allowing fleets of contracts sharing the same code to upgrade atomically through a single reference update. CAP-86 adds sparse host functions that handle missing or extra data fields during migrations, addressing cases where contracts have been stuck unable to evolve their data structures.

The timeline is fixed: core stable release landed Aug. 13, infrastructure and SDK releases run through Aug. 21, the testnet vote is Aug. 27 at 17:00 UTC, and the mainnet vote follows Sept. 16 at 17:00 UTC. Builders using SDK-based integrations must update before Aug. 27 for testnet and before Sept. 16 for mainnet.

CAP-85 ends the half-upgraded fleet problem

Many protocols deploy dozens or hundreds of copies of the same contract — a fleet sharing identical underlying code. When that code needs a security fix or feature update, admins previously had to update each instance individually. For large fleets, that couldn't be done in a single transaction, leaving a window where some contracts ran new code while others remained on the old version.

CAP-85 introduces an externally managed executable: contracts can point to a shared, updatable code reference owned by another contract. Updating that single reference upgrades every connected contract at once, atomically, regardless of fleet size. The pattern mirrors the "beacon proxy" approach used on Ethereum and other chains.

Aug. 27 testnet vote opens the rollout window

Stellar has published a fixed schedule for Adapter. The core stable release went out Aug. 13, with infrastructure and SDK releases following through Aug. 21. The testnet upgrade vote takes place Aug. 27 at 17:00 UTC, and the mainnet vote follows Sept. 16 at 17:00 UTC.

Protocol 28 also adds sparse map host functions so contracts can handle missing or extra fields more gracefully during migrations. Operators of typical SDK-based integrations should bump their SDK version before Aug. 27 for testnet builds and before Sept. 16 for mainnet builds. Validators, infrastructure operators, wallets, exchanges, and issuers each have specific preparation steps detailed in Stellar's Protocol 28 Upgrade Guide.

The upgrade continues a pattern of recent Stellar protocol releases focused on making the network a more capable platform for real financial applications without sacrificing the speed and low cost the network is known for. For XLM holders, the upgrade could attract more developer activity to the Soroban platform, potentially driving increased on-chain usage. Stellar's work with DTCC on tokenizing real-world assets shows the network's push into institutional finance.

This article is for informational purposes only and does not constitute investment advice.