Fireblocks updates the API Co-signer software to include stability enhancements and new features. This article details the most recent AWS Nitro Co-signer versions. Always use the latest version listed here for optimal performance.

Latest version

Version 2026.03.02 (March 2026)

Version hash: 95a317d3c7

Added support for POLICY_CHANGE approval request type (the customer co-signer can now approve policy changes via Policy Service v2)
Performance improvements and bug fixes

Version history

Version 2026.01.29 (January 2026)

Version hash: 340d9f6057

Bug fixes and performance improvements

Version 2025.12.30 (December 2025)

Version hash: a294449c1b

Added support for "Protected Tags" approval requests

Version 2025.12.11 (December 2025)

Version hash: c44604398e

The callback can now return a “retry” response in an exchange withdraw operation

Version 2025.11.20 (November 2025)

Version hash: 82a5cc0078

Fixed a bug that may cause the Co-signer not to load correctly after a graceful shutdown

Version 2025.10.09 (October 2025)

Version hash: 4e34888c01

Fixed bug parsing messages after websocket reconnect
Fixed bug sending messages on half closed websocket connections

Version 2025.08.12 (August 2025; US environments only)

Version hash: 19c07421dc

Fixed WebSocket bug causing performance issues

Version 2025.07.16 (July 2025)

Version hash: bb61e507

Fixed bugs and increased performance
Better support for web sockets

Version 2.1.1 (April 2025)

Version hash: 7160d7b833

Bug fixes and performance improvements

Version 2.0.5 (September 2024)

Version hash: d177e696c3

Decreased signing latency along with general performance increases
Extended filtering of environment variables
Improvements to key handling within the enclave
Bug fixes

Version 2.0.4 (August 2024)

Version hash: 41d1888dc8

Fixed the issue when setting AWS region using environment variables
Removed unnecessary testing artifacts

Version 2.0.2 (August 2024)

Modified KMS CMK ARN prompt
Added start, stop and restart commands
Added echo to show where logs are saved to
Fixed AWS NTP sync issue
Fixed Callback Handler public key issue on install
Removed unnecessary testing artifacts

Version 2.0.1 (July 2024)

Added check for force flag and existence of destination before the user is prompted for details
Added route DNS queries to the DNS server defined on the host EC2 instance

Version 2.0.0 (June 2024)

Initial release