1.5.59 January 27th, 2026

Akka.NET v1.5.59 is a maintenance release with critical bug fixes and new features for observability.

Critical Bug Fixes

• Fix MergeSeen to filter Seen against current Members - Fixes issue #8009. Resolves a cluster gossip serialization failure that could occur with the error "Unknown address in cluster message" when the Seen table contained addresses of members that had already left the cluster.

Bug Fixes

• Fix logger initialization continuation race in LoggingBus - Fixes a race condition during logger initialization that could cause logging failures during actor system startup.
• Fix Inbox.AwaitResult throwing AggregateException instead of TimeoutException - Inbox.AwaitResult now correctly throws TimeoutException when a timeout occurs, rather than wrapping it in an AggregateException.
• Fix DeferAsync async handler nesting bug in CommandAsync - Fixes issue #7998. Resolves an issue where DeferAsync with an async handler would throw "RunTask calls cannot be nested" when called from CommandAsync.
• Fix AwaitAssertAsync logic causing premature timeout - Fixes AwaitAssertAsync in Akka.TestKit to correctly wait for the full timeout duration before failing assertions.

New Features

• Add ActivityContext capture to LogEvent for trace correlation - Log events now automatically capture the current System.Diagnostics.ActivityContext when created, enabling correlation between Akka.NET logs and distributed traces in observability platforms like OpenTelemetry, Application Insights, and Jaeger.
• Add BroadcastHub startAfterNrOfConsumers parameter - Fixes issue #8017. Port from Apache Pekko - adds a startAfterNrOfConsumers parameter to BroadcastHub.Sink<T>() that delays broadcasting until the specified number of consumers have subscribed:

  // Wait for 3 consumers before starting to broadcast
  var sink = BroadcastHub.Sink<int>(startAfterNrOfConsumers: 3, bufferSize: 256);
  

Improvements

• CoordinatedShutdown: clearly log the reason why we're exiting - CoordinatedShutdown now logs the specific reason for shutdown at INFO level, making it easier to diagnose why an actor system terminated.

To see the full set of changes in Akka.NET v1.5.59, click here.

Changes:

• 85889e2d49ee75a3161eff115c08809ffed1cce0 Update version to 1.5.59 in Directory.Build.props
• bbb70873e69e4fcfc17bac8b2d018f4589a0fc3d Add release notes for Akka.NET v1.5.59 [ #8011 ]
• f7b77584fdd8dd791b7c75b2b8834c365e23d4d1 Update API approval files for 1.5.59 backport
• b1d6d10591d262fb4d10e55e8a2e669be5fed4d6 Fix MergeSeen to filter Seen against current Members (#8009) (#8011)
• da692cb3fbf740eea1a1fdc1bab712985e1a2472 Add ActivityContext capture to LogEvent for trace correlation (#7995) [ #6855 ]
• 1ada6355729b01dd2d6698d332c318c753ff4622 Fix logger initialization continuation race in LoggingBus (#8006)
• 5284e131bafc373ead85d29993eb4682ac65fdca Add BroadcastHub startAfterNrOfConsumers parameter (#8017) (#8018) [ #275, #1841 ]
• 99b00c5d24024d28997309e4571bc4f15d9ee9b5 Fix Inbox.AwaitResult throwing AggregateException instead of TimeoutException (#8005)
• 7e18fb8067ac959636a1f3e4fd7bce3f7879baac Fix DeferAsync async handler nesting bug in CommandAsync (#7998) (#7999)
• bc85915839ffa45be04407e87f9b737a766c65f4 CoordinatedShutdown: clearly log the reason why we're exiting (#7988)