akkadotnet/akka.net 1.6.0-beta5

Akka.NET v1.6.0-beta5

on GitHub

1.6.0-beta5 November 4th, 2026

Akka.NET 1.6.0-beta5 removes [AkkaUnion] in favor of inferring unions from the property type, teaches the source generator to serialize C# 15 union types, and fixes a sharding producer-controller crash plus four Akka.Streams bugs. Read the v1.6 getting started guide for the full upgrade path.

Serialization V2

• A property typed as an interface, an abstract class, or a closed hierarchy is now a union over every [AkkaSerializable] type that implements or derives from it - no attribute needed. AkkaUnionAttribute is deleted, and AKKASG018, AKKASG038, AKKASG049 and AKKASG050 retire with it. Framework types and collection-like types are never inferred. The wire format is unchanged. (#8890)
• C# 15 union types work as field types. The generator detects a union as a struct implementing IUnion, uses its public single-parameter constructors as the member set, and dispatches on Value. TUnion? and default(TUnion) both read back as null. (#8888)
• [AkkaSerializable<T>] is renamed to [AkkaSerializerIncludes<T>]. A non-generic included type now takes its manifest from its own [AkkaSerializable(Manifest = ...)]; setting Manifest on the include of a non-generic type is the new AKKASG053 error. Closed generic constructions keep Manifest/ManifestPrefix on the include. (#8891)
• AKKASG048 fails the build when a concrete implementor in the compilation lacks [AkkaSerializable], and AKKASG019 now fires on an empty discovered union instead of emitting a dispatch helper with no arms. AKKASG025 (unsealed union member) is now a Warning instead of Info. (#8887)
• New AKKASG052 catches a property typed as a concrete, non-sealed nested value class that some class in the compilation derives from - the property would be written as the base's own fields and lose the subclass state. (#8890)

Akka.Streams

• Dispose() on the ActorSystem's shared default materializer no longer shuts it down for every user of the system. A using block, a scoped DI registration, or an actor disposing it in PostStop used to break system.Materializer() and every later materialization. The ActorSystem still stops it on termination, and Shutdown() still stops it explicitly. (#8895, fixes #8885)
• SourceRef now honors StreamRefAttributes for buffer capacity, demand redelivery interval and final termination signal deadline, falling back to StreamRefSettings when no attribute is set. (#8880, fixes #8878)
• StreamRefSettings now initializes FinalTerminationSignalDeadline from its constructor, and gains a WithFinalTerminationSignalDeadline method. (#8877)
• Deferred stream operators now pass inherited attributes through when they materialize their inner graph, so attributes set above a LazySource, LazySink or Setup stage reach the stages inside it. (#8842)
• Flow.Setup forwards its input correctly instead of dropping elements. (#8839)

Akka.Cluster.Sharding

• ShardingProducerController no longer throws InvalidActorNameException and restarts when a message arrives for an entity whose delivery child is still terminating. Cleanup now marks the entity as stopping and buffers for it, and the entry is removed only once the child's name is free. Producer demand keeps flowing while the child stops. (#8869, fixes #8850)

Internal

• NuGet publishing moves to GitHub Actions trusted publishing, replacing the Windows release pipeline. (#8892)
• ReliableDeliveryShardingSpec no longer races on a legal at-least-once duplicate of msg-3. (#8894)

2 contributors since release 1.6.0-beta4