Canton 3.7.0 Released With Protocol Version 37, Faster CantonBFT Ordering and Breaking API Changes
The minor release, published on 29 October 2026, drops the multi-synchronizer feature flag on protocol version 37, adds topology support for Hybrid Party Replication and tightens default configuration.
Canton 3.7.0 was released on 29 October 2026, according to release notes published on the digital-asset/canton GitHub repository. The minor release introduces protocol version 37 and brings changes across multi-synchronizer support, party replication, the CantonBFT ordering layer, traffic management and node hardening.
The release carries breaking changes in the Ledger API, node APIs and console, protocol and configuration. The notes state that synchronizers running protocol version 36 are not affected, and that protocol version 37 will be rolled out as a new protocol version.
Main themes of the release
The release notes list five main areas of change:
- Multi-synchronizer: no feature flag is needed on protocol version 37, and the Ledger API changes for multi-synchronizer applications.
- Party replication: new
v31 topology transactions track the hosting state of each participant of a party, to enable Hybrid Party Replication (HyPR). Applications that decode PartyToParticipant transactions may need to act, and the notes include a migration guide for external signers.
- CantonBFT: lower ordering latency and faster catch-up and onboarding.
- Traffic management: traffic can be purchased for participants before they register with the sequencer, and cost estimation now covers reassignments.
- Hardening and scalability: protocol version 37 bounds more protocol, topology and ACS commitment collections, and sequencer and topology states larger than 2 GB can be exported and imported.
Breaking changes for operators and developers
On the Ledger API, StateService now excludes incomplete reassignments unless includeIncompleteReassignments is set, and rejects continuation and page tokens from previous versions. GenerateExternalPartyTopology returns v31 topology transactions on protocol version 37 unless protocol version 36 is explicitly requested. Contracts with a non-zero reassignment counter that repair commands import, add or purge now appear as Assigned and Unassigned events.
For node APIs and the console, sequencers and mediators no longer store their onboarding transactions, and operators are directed to use generate_onboarding_transactions instead of identity_transactions. The propose_delta command no longer moves an Active participant back to Onboarding.
Default configuration values were changed for safety. The participant repair service is now disabled by default, as is key export. The notes also state that the Docker images no longer set canton.parameters.non-standard-config = true.
Integration work in Splice
Integration of Canton 3.7 into the canton-network/splice repository has been under way in pull request #7746, opened on 13 October 2026 by a Digital Asset contributor. The work switched test environments to protocol version 37 and adjusted bootstrap scripts for the new sequencer and mediator initialization behaviour.
During review, a maintainer cautioned that the main branch could not be switched over "until we have proper data continuity", and an upgrade test failure was tracked in a follow-up issue. The maintainer approved the changes on 14 October and wrote on 16 October that he was merging the pull request, while asking for a follow-up on a remaining code question about onboarding transactions.
Why it matters
Canton 3.7.0 sets the software base for protocol version 37, which the release notes say will be introduced as a new protocol version rather than changing existing protocol version 36 synchronizers. Application builders that use StateService pagination, external party topology or decode PartyToParticipant transactions face breaking changes and should review the migration guidance. Node operators should note the safer configuration defaults and the new onboarding transaction commands for sequencers and mediators.
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Written by CantonCap's automated news desk from the sources below.
Sources
Cover photo: Racks Amravati Data Center by PiDatacenters, CC BY-SA 4.0, via Wikimedia Commons, cropped.
