Adapter Protocol 28: Stellar Sets Dates for Major Upgrade

Adapter Protocol 28: Stellar Upgrade Rollout Starts This Month

Stellar is preparing for its next network-wide upgrade, and the details are now official. 

The Stellar Development Foundation confirmed the rollout plan for Adapter Protocol 28.

Source: BuildOnStellar on X

Unlike some past upgrades that focused mainly on infrastructure, Adapter Protocol 28 is built with developers in mind. 

Two of its three core changes are aimed directly at making life easier for people building smart contracts on Soroban, Stellar's smart contract platform, while the third strengthens how the network itself reaches consensus.

What's Actually Changing With Adapter Protocol 28

The upgrade bundles three separate proposals, known on Stellar as CAPs, or Core Advancement Proposals. Together, they make up the full scope of Adapter Protocol 28:

• CAP-83 – improves consensus performance, especially when the network is under load

• CAP-85 – allows atomic upgrades across entire fleets of smart contracts

• CAP-86 – makes it easier for contracts to migrate their data without breaking

Each one solves a different problem, and Stellar has explained the reasoning behind them in detail.

Consensus That Doesn't Wait Around

Validators, the machines responsible for confirming transactions, normally need a full transaction set before they can move forward with consensus. If that data is slow to arrive, the whole process can stall.

CAP-83 changes this. Validators can now start voting before a transaction set has fully landed, and they get a clean way to simply drop a set that's late or broken instead of freezing up. 

Source: @BuildOnStellar on X

Stellar says this keeps the network moving smoothly even under heavy load, and it's a change most builders won't need to lift a finger for. The performance benefits will roll out gradually after mainnet as a related feature, parallel transaction-set downloading, gets switched on in phases.

No More Half-Upgraded Contract Fleets

Here's a problem a lot of Stellar projects have run into: when you deploy dozens or hundreds of copies of the same contract, updating all of them at once hasn't been possible. 

Large fleets had to be upgraded one by one, which meant some contracts ran the new code while others were stuck on the old version, sometimes for a while.

CAP-85 fixes that. It introduces a shared, updatable code reference that multiple contracts can point back to. 

Source: X of BuildOnStellar

Change that single reference, and every connected contract upgrades at the same moment, no matter how many there are. Developers who've worked on other chains will recognize the concept, it's similar to the "beacon proxy" pattern used elsewhere in the industry.

Contract Data That Can Actually Evolve

Smart contracts rarely stay static. Fields get added, old ones get dropped, and interfaces change over time. The trouble is that Stellar's current system rejects any data that doesn't match the exact expected structure, which has made these kinds of changes riskier than they should be and in some cases has left contracts stuck entirely.

CAP-86 solves this with new "sparse" host functions that can handle missing or extra fields instead of failing outright. 

Source: BOS on X

Teams get access to this simply by rebuilding against the updated SDK. Nothing about how contracts are written needs to change.

The Timeline Builders Need to Know

Stellar has laid out a fixed schedule for Adapter Protocol 28, and it's worth marking on the calendar:

• August 13, 2026 – Stellar Core stable release goes live

• August 13–21, 2026 – Infrastructure and SDK releases follow

• August 27, 2026, 17:00 UTC – Testnet upgrade vote

• September 16, 2026, 17:00 UTC – Mainnet upgrade vote

Source: Build on Stellar on X

Stellar's advice for typical SDK-based integrations is simple: update before August 27 for testnet, and before September 16 for mainnet. Validators, infrastructure operators, wallets, exchanges, and issuers each have their own checklist, which is laid out in full in Stellar's Protocol 28 Upgrade Guide.

What Comes Next

For now, the focus shifts to the testnet vote on August 27, followed by the mainnet vote three weeks later. Stellar blockchain hasn't indicated any changes to this schedule as of writing. 

Teams building on the network are being encouraged to start preparing early rather than waiting until the last week and to keep an eye on Stellar's Developer Discord, where the community is actively coordinating the upgrade in the 

Source: official BOS source

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