What Zipper Actually Changes Stellar's Protocol 27, named Zipper, is set for a mainnet validator vote on July 8. The upgrade centres on a single but consequential change: making authenticatio
Stellar's Protocol 27, named Zipper, is set for a mainnet validator vote on July 8. The upgrade centres on a single but consequential change: making authentication delegation a first-class feature on Stellar, meaning one account can officially authorise another to act on its behalf.
Before Zipper, delegation existed on Stellar only as an accidental side effect. Developers who tried to use it faced a tangle of manual steps, extra simulation passes, and bloated transaction sizes, so most teams avoided it entirely. Zipper turns that workaround into a clean, supported tool.
In practical terms, the upgrade opens the door to features that have been difficult or impossible to build cleanly until now. Cheaper transactions and more flexible account designs, including social recovery, delegated signing keys, and modular multisig, become practical to build. Transactions also become smaller and cheaper because all delegated signers bundle into a single authorisation entry instead of requiring separate ones.
On the security side, CAP-0071-02 adds address-bound Soroban credentials, closing a narrow replay vulnerability where accounts sharing private keys could be exposed to cross-account signature reuse.
Zipper's significance extends beyond what it ships on day one. CAP-0071-01 is explicitly foundational to CAP-0072, which adds contract-based authentication to classic Stellar accounts. The delegation mechanism introduced here is the same one that more visible features in future protocols will depend on.
The Stellar Development Foundation has confirmed that Protocol 28 will bring contract-based authentication to classic Stellar accounts, the standard ones most users hold today, and the delegation mechanism in Zipper is a direct prerequisite for that. In effect, what validators are being asked to approve on July 8 is as much an infrastructure decision as a feature release.
The release timeline ran as follows: Stellar Core shipped June 5, RPC and Galexie on June 10, SDKs between June 5 and 11, Horizon on June 12, and the testnet upgrade on June 18, ahead of the mainnet protocol vote on July 8.
Sources:Stellar Development Foundation: Zipper, Protocol 27 Upgrade GuideStellar Docs: Software Versions and Protocol FeaturesGitHub: Stellar Core v27.0.0 Release Notes
