1.5.67 April 26th 2026

New Features

• Add WithStrictSerialization helper — resolves issue #734. Adds WithStrictSerialization(bool enabled = true) extension on AkkaConfigurationBuilder that sets akka.actor.serialization-settings.allow-unregistered-types = off, disabling the Newtonsoft.Json fallback and throwing SerializationException for unregistered types.

Updates

• Bump Akka version from 1.5.66 to 1.5.67 - Hotfix release reverting the Task.Yield() optimization in AsyncWriteJournal/SnapshotStore that broke the persistence plugin threading contract.