diff --git a/src/contrib/cluster/Akka.Cluster.Metrics/Serialization/ClusterMetricsMessageSerializer.cs b/src/contrib/cluster/Akka.Cluster.Metrics/Serialization/ClusterMetricsMessageSerializer.cs
index 6574cae9438..8f7b110d8c9 100644
--- a/src/contrib/cluster/Akka.Cluster.Metrics/Serialization/ClusterMetricsMessageSerializer.cs
+++ b/src/contrib/cluster/Akka.Cluster.Metrics/Serialization/ClusterMetricsMessageSerializer.cs
@@ -44,6 +44,12 @@ public ClusterMetricsMessageSerializer(ExtendedActorSystem system)
             _serialization = new Lazy<Akka.Serialization.Serialization>(() => new Akka.Serialization.Serialization(system));
         }
         
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterMetricsMessageSerializer) ? 10 : base.Identifier;
+
         /// <inheritdoc />
         public override byte[] ToBinary(object obj)
         {
diff --git a/src/contrib/cluster/Akka.Cluster.Sharding/Serialization/ClusterShardingMessageSerializer.cs b/src/contrib/cluster/Akka.Cluster.Sharding/Serialization/ClusterShardingMessageSerializer.cs
index 71dc3b2a265..3dc9c748f8d 100644
--- a/src/contrib/cluster/Akka.Cluster.Sharding/Serialization/ClusterShardingMessageSerializer.cs
+++ b/src/contrib/cluster/Akka.Cluster.Sharding/Serialization/ClusterShardingMessageSerializer.cs
@@ -148,6 +148,12 @@ public ClusterShardingMessageSerializer(ExtendedActorSystem system) : base(syste
             };
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterShardingMessageSerializer) ? 13 : base.Identifier;
+
         private ShardingEnvelope ShardingEnvelopeFromBinary(byte[] bytes)
         {
             var proto = Proto.Msg.ShardingEnvelope.Parser.ParseFrom(bytes);
diff --git a/src/contrib/cluster/Akka.Cluster.Tools/Client/Serialization/ClusterClientMessageSerializer.cs b/src/contrib/cluster/Akka.Cluster.Tools/Client/Serialization/ClusterClientMessageSerializer.cs
index dbb55b2c731..67d19516c81 100644
--- a/src/contrib/cluster/Akka.Cluster.Tools/Client/Serialization/ClusterClientMessageSerializer.cs
+++ b/src/contrib/cluster/Akka.Cluster.Tools/Client/Serialization/ClusterClientMessageSerializer.cs
@@ -48,6 +48,12 @@ public ClusterClientMessageSerializer(ExtendedActorSystem system) : base(system)
             _payloadSupport = new WrappedPayloadSupport(system);
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterClientMessageSerializer) ? 15 : base.Identifier;
+
         /// <summary>
         /// Serializes the given object into a byte array
         /// </summary>
diff --git a/src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/Serialization/DistributedPubSubMessageSerializer.cs b/src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/Serialization/DistributedPubSubMessageSerializer.cs
index c37c81fae02..7e53c8ec40d 100644
--- a/src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/Serialization/DistributedPubSubMessageSerializer.cs
+++ b/src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/Serialization/DistributedPubSubMessageSerializer.cs
@@ -55,6 +55,12 @@ public DistributedPubSubMessageSerializer(ExtendedActorSystem system) : base(sys
             };
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(DistributedPubSubMessageSerializer) ? 9 : base.Identifier;
+
         /// <summary>
         /// Serializes the given object into a byte array
         /// </summary>
diff --git a/src/contrib/cluster/Akka.Cluster.Tools/Singleton/Serialization/ClusterSingletonMessageSerializer.cs b/src/contrib/cluster/Akka.Cluster.Tools/Singleton/Serialization/ClusterSingletonMessageSerializer.cs
index a5ef3e6fee2..f7f2a1ffd91 100644
--- a/src/contrib/cluster/Akka.Cluster.Tools/Singleton/Serialization/ClusterSingletonMessageSerializer.cs
+++ b/src/contrib/cluster/Akka.Cluster.Tools/Singleton/Serialization/ClusterSingletonMessageSerializer.cs
@@ -41,6 +41,12 @@ public ClusterSingletonMessageSerializer(ExtendedActorSystem system) : base(syst
             };
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterSingletonMessageSerializer) ? 14 : base.Identifier;
+
         /// <summary>
         /// Serializes the given object into a byte array
         /// </summary>
diff --git a/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatedDataSerializer.cs b/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatedDataSerializer.cs
index d18dfb7b691..fa026096a77 100644
--- a/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatedDataSerializer.cs
+++ b/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatedDataSerializer.cs
@@ -75,6 +75,8 @@ public ReplicatedDataSerializer(ExtendedActorSystem system) : base(system)
                 system.Settings.Config.GetBoolean("akka.cluster.sharding.distributed-data.backward-compatible-wire-format");
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 11;
 
         public override byte[] ToBinary(object obj)
         {
diff --git a/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatorMessageSerializer.cs b/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatorMessageSerializer.cs
index 562f01ad19e..5771645936b 100644
--- a/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatorMessageSerializer.cs
+++ b/src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatorMessageSerializer.cs
@@ -168,6 +168,9 @@ public ReplicatorMessageSerializer(Akka.Actor.ExtendedActorSystem system) : base
             });
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 12;
+
         public override string Manifest(object o)
         {
             switch (o)
diff --git a/src/core/Akka.API.Tests/BuiltInSerializerIdentifierSpec.cs b/src/core/Akka.API.Tests/BuiltInSerializerIdentifierSpec.cs
new file mode 100644
index 00000000000..b199f40a1bb
--- /dev/null
+++ b/src/core/Akka.API.Tests/BuiltInSerializerIdentifierSpec.cs
@@ -0,0 +1,66 @@
+//-----------------------------------------------------------------------
+// <copyright file="BuiltInSerializerIdentifierSpec.cs" company="Akka.NET Project">
+//     Copyright (C) 2009-2025 Lightbend Inc. <http://www.lightbend.com>
+//     Copyright (C) 2013-2025 .NET Foundation <https://github.com/akkadotnet/akka.net>
+// </copyright>
+//-----------------------------------------------------------------------
+
+using System;
+using System.Runtime.CompilerServices;
+using Akka.Actor;
+using Akka.Cluster.Metrics;
+using Akka.Cluster.Sharding;
+using Akka.Cluster.Tools.Client;
+using Akka.Cluster.Tools.PublishSubscribe;
+using Akka.Cluster.Tools.Singleton;
+using Akka.Configuration;
+using Akka.Serialization;
+using Akka.Streams;
+using Xunit;
+using DistributedDataExtension = Akka.DistributedData.DistributedData;
+using PersistenceExtension = Akka.Persistence.Persistence;
+
+namespace Akka.API.Tests
+{
+    /// <summary>
+    /// Every built-in serializer now declares its wire id in code. This is the one project that references all of
+    /// Remote, Cluster, Cluster.Tools, Cluster.Sharding, DistributedData, Cluster.Metrics, Persistence, Streams and
+    /// core, so it's the one place that can check every built-in serializer's code <see cref="Serializer.Identifier"/>
+    /// against every module's shipped <c>akka.actor.serialization-identifiers</c> row in a single test.
+    ///
+    /// Each serializer is created with <see cref="RuntimeHelpers.GetUninitializedObject"/>, which skips the
+    /// constructor entirely, leaving the instance's actor-system field null. A built-in serializer's <c>Identifier</c>
+    /// is either a hardcoded constant or a <c>GetType()</c> guard around one - never a HOCON read - so this is safe
+    /// for all of them. It also proves D1: a serializer that still resolved its id lazily from HOCON would touch the
+    /// null actor-system field on first access and throw, instead of quietly returning the right answer.
+    /// </summary>
+    public class BuiltInSerializerIdentifierSpec
+    {
+        [Fact(DisplayName = "Should_match_HOCON_serialization_identifiers_When_reading_every_builtin_serializer_Identifier")]
+        public void Should_match_HOCON_serialization_identifiers_When_reading_every_builtin_serializer_Identifier()
+        {
+            var config = ConfigurationFactory.FromResource<Remote.RemoteSettings>("Akka.Remote.Configuration.Remote.conf")
+                .WithFallback(ConfigurationFactory.FromResource<Cluster.ClusterSettings>("Akka.Cluster.Configuration.Cluster.conf"))
+                .WithFallback(ClusterSharding.DefaultConfig())
+                .WithFallback(ClusterSingleton.DefaultConfig())
+                .WithFallback(DistributedPubSub.DefaultConfig())
+                .WithFallback(ClusterClientReceptionist.DefaultConfig())
+                .WithFallback(DistributedDataExtension.DefaultConfig())
+                .WithFallback(ClusterMetrics.DefaultConfig())
+                .WithFallback(PersistenceExtension.DefaultConfig())
+                .WithFallback(ActorMaterializer.DefaultConfig());
+
+            // config only: no ActorSystem needed to read the rows
+            var rows = config.WithFallback(ConfigurationFactory.Default()).GetConfig("akka.actor.serialization-identifiers");
+            foreach (var row in rows.AsEnumerable())
+            {
+                var type = Type.GetType(row.Key, throwOnError: true);
+                var expectedId = row.Value.GetInt();
+
+                var serializer = (Serializer)RuntimeHelpers.GetUninitializedObject(type);
+                Assert.True(expectedId == serializer.Identifier,
+                    $"{type.FullName} declared Identifier {serializer.Identifier}, but its HOCON row says {expectedId}");
+            }
+        }
+    }
+}
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.DotNet.verified.txt
index c6e251644ad..7c735f2cf4d 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.DotNet.verified.txt
@@ -447,6 +447,7 @@ namespace Akka.Cluster.Serialization
     public class ClusterMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.Net.verified.txt
index fd0a4eef4a5..7b1b47ea628 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.Net.verified.txt
@@ -447,6 +447,7 @@ namespace Akka.Cluster.Serialization
     public class ClusterMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.DotNet.verified.txt
index 1546014be53..b94fd4a9c24 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.DotNet.verified.txt
@@ -280,6 +280,7 @@ namespace Akka.Cluster.Metrics.Serialization
     public class ClusterMetricsMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMetricsMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.Net.verified.txt
index df6f6dff572..aff1e3df1c1 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.Net.verified.txt
@@ -280,6 +280,7 @@ namespace Akka.Cluster.Metrics.Serialization
     public class ClusterMetricsMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMetricsMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.DotNet.verified.txt
index c11cce02217..3ccd5f60715 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.DotNet.verified.txt
@@ -581,6 +581,7 @@ namespace Akka.Cluster.Sharding.Serialization
     public class ClusterShardingMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterShardingMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.Net.verified.txt
index 6e7b5561fcf..9f54ca1ffe7 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.Net.verified.txt
@@ -581,6 +581,7 @@ namespace Akka.Cluster.Sharding.Serialization
     public class ClusterShardingMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterShardingMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.DotNet.verified.txt
index d67af4853e1..6a65bffda6d 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.DotNet.verified.txt
@@ -214,6 +214,7 @@ namespace Akka.Cluster.Tools.Client.Serialization
     public class ClusterClientMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterClientMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -423,6 +424,7 @@ namespace Akka.Cluster.Tools.PublishSubscribe.Serialization
     public class DistributedPubSubMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public DistributedPubSubMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -584,6 +586,7 @@ namespace Akka.Cluster.Tools.Singleton.Serialization
     public class ClusterSingletonMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterSingletonMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.Net.verified.txt
index 98ed12298c9..9211b95af79 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.Net.verified.txt
@@ -214,6 +214,7 @@ namespace Akka.Cluster.Tools.Client.Serialization
     public class ClusterClientMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterClientMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -423,6 +424,7 @@ namespace Akka.Cluster.Tools.PublishSubscribe.Serialization
     public class DistributedPubSubMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public DistributedPubSubMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -584,6 +586,7 @@ namespace Akka.Cluster.Tools.Singleton.Serialization
     public class ClusterSingletonMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterSingletonMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.DotNet.verified.txt
index 049d4228463..478d2d92e74 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.DotNet.verified.txt
@@ -5158,6 +5158,7 @@ namespace Akka.Serialization
     public class ByteArraySerializer : Akka.Serialization.SerializerV2
     {
         public ByteArraySerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object Deserialize(System.Buffers.ReadOnlySequence<byte> bytes, string manifest) { }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override object FromBinary(byte[] bytes, string manifest) { }
@@ -5183,6 +5184,7 @@ namespace Akka.Serialization
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Configuration.Config config) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Serialization.NewtonSoftJsonSerializerSettings settings) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public object Serializer { get; }
         public Newtonsoft.Json.JsonSerializerSettings Settings { get; }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.Net.verified.txt
index 9b0cfe0a887..f6ab3fe0eb5 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.Net.verified.txt
@@ -5147,6 +5147,7 @@ namespace Akka.Serialization
     public class ByteArraySerializer : Akka.Serialization.SerializerV2
     {
         public ByteArraySerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object Deserialize(System.Buffers.ReadOnlySequence<byte> bytes, string manifest) { }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override object FromBinary(byte[] bytes, string manifest) { }
@@ -5172,6 +5173,7 @@ namespace Akka.Serialization
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Configuration.Config config) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Serialization.NewtonSoftJsonSerializerSettings settings) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public object Serializer { get; }
         public Newtonsoft.Json.JsonSerializerSettings Settings { get; }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.DotNet.verified.txt
index 497781a86ec..55f318f263d 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.DotNet.verified.txt
@@ -1122,6 +1122,7 @@ namespace Akka.DistributedData.Serialization
     public sealed class ReplicatedDataSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatedDataSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -1129,6 +1130,7 @@ namespace Akka.DistributedData.Serialization
     public sealed class ReplicatorMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatorMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.Net.verified.txt
index c4220094b54..a2365167074 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.Net.verified.txt
@@ -1122,6 +1122,7 @@ namespace Akka.DistributedData.Serialization
     public sealed class ReplicatedDataSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatedDataSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -1129,6 +1130,7 @@ namespace Akka.DistributedData.Serialization
     public sealed class ReplicatorMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatorMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.DotNet.verified.txt
index 561959a1b63..e49cfef947b 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.DotNet.verified.txt
@@ -1256,6 +1256,7 @@ namespace Akka.Persistence.Serialization
     public sealed class PersistenceMessageSerializer : Akka.Serialization.Serializer
     {
         public PersistenceMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -1263,6 +1264,7 @@ namespace Akka.Persistence.Serialization
     public class PersistenceSnapshotSerializer : Akka.Serialization.Serializer
     {
         public PersistenceSnapshotSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.Net.verified.txt
index 4ee34bd39ac..1004e5039a6 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.Net.verified.txt
@@ -1256,6 +1256,7 @@ namespace Akka.Persistence.Serialization
     public sealed class PersistenceMessageSerializer : Akka.Serialization.Serializer
     {
         public PersistenceMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -1263,6 +1264,7 @@ namespace Akka.Persistence.Serialization
     public class PersistenceSnapshotSerializer : Akka.Serialization.Serializer
     {
         public PersistenceSnapshotSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.DotNet.verified.txt
index e20f156893a..1603f75248a 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.DotNet.verified.txt
@@ -428,6 +428,7 @@ namespace Akka.Remote.Serialization
     public class DaemonMsgCreateSerializer : Akka.Serialization.Serializer
     {
         public DaemonMsgCreateSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -435,6 +436,7 @@ namespace Akka.Remote.Serialization
     public class MessageContainerSerializer : Akka.Serialization.Serializer
     {
         public MessageContainerSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -442,6 +444,7 @@ namespace Akka.Remote.Serialization
     public sealed class MiscMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public MiscMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object obj) { }
         public override byte[] ToBinary(object obj) { }
@@ -449,6 +452,7 @@ namespace Akka.Remote.Serialization
     public sealed class PrimitiveSerializers : Akka.Serialization.SerializerWithStringManifest
     {
         public PrimitiveSerializers(Akka.Actor.ExtendedActorSystem system, Akka.Configuration.Config config) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object obj) { }
         public override byte[] ToBinary(object obj) { }
@@ -456,6 +460,7 @@ namespace Akka.Remote.Serialization
     public class ProtobufSerializer : Akka.Serialization.Serializer
     {
         public ProtobufSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -463,6 +468,7 @@ namespace Akka.Remote.Serialization
     public sealed class SystemMessageSerializer : Akka.Serialization.Serializer
     {
         public SystemMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.Net.verified.txt
index 5637795f550..710553dcb1d 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveRemote.Net.verified.txt
@@ -428,6 +428,7 @@ namespace Akka.Remote.Serialization
     public class DaemonMsgCreateSerializer : Akka.Serialization.Serializer
     {
         public DaemonMsgCreateSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -435,6 +436,7 @@ namespace Akka.Remote.Serialization
     public class MessageContainerSerializer : Akka.Serialization.Serializer
     {
         public MessageContainerSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -442,6 +444,7 @@ namespace Akka.Remote.Serialization
     public sealed class MiscMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public MiscMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object obj) { }
         public override byte[] ToBinary(object obj) { }
@@ -449,6 +452,7 @@ namespace Akka.Remote.Serialization
     public sealed class PrimitiveSerializers : Akka.Serialization.SerializerWithStringManifest
     {
         public PrimitiveSerializers(Akka.Actor.ExtendedActorSystem system, Akka.Configuration.Config config) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object obj) { }
         public override byte[] ToBinary(object obj) { }
@@ -456,6 +460,7 @@ namespace Akka.Remote.Serialization
     public class ProtobufSerializer : Akka.Serialization.Serializer
     {
         public ProtobufSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
@@ -463,6 +468,7 @@ namespace Akka.Remote.Serialization
     public sealed class SystemMessageSerializer : Akka.Serialization.Serializer
     {
         public SystemMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.DotNet.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.DotNet.verified.txt
index 72fbdfa87aa..a859684a446 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.DotNet.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.DotNet.verified.txt
@@ -4792,6 +4792,7 @@ namespace Akka.Streams.Serialization
     public sealed class StreamRefSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public StreamRefSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object o) { }
diff --git a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.Net.verified.txt b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.Net.verified.txt
index 87cd5551256..40182de3ff0 100644
--- a/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.Net.verified.txt
+++ b/src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveStreams.Net.verified.txt
@@ -4791,6 +4791,7 @@ namespace Akka.Streams.Serialization
     public sealed class StreamRefSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public StreamRefSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object o) { }
diff --git a/src/core/Akka.Cluster/Serialization/ClusterMessageSerializer.cs b/src/core/Akka.Cluster/Serialization/ClusterMessageSerializer.cs
index b8fec3211c4..b6e8adc6394 100644
--- a/src/core/Akka.Cluster/Serialization/ClusterMessageSerializer.cs
+++ b/src/core/Akka.Cluster/Serialization/ClusterMessageSerializer.cs
@@ -72,6 +72,12 @@ public ClusterMessageSerializer(ExtendedActorSystem system) : base(system)
            
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterMessageSerializer) ? 5 : base.Identifier;
+
         public override byte[] ToBinary(object obj)
         {
             switch (obj)
diff --git a/src/core/Akka.Cluster/Serialization/ReliableDeliverySerializer.cs b/src/core/Akka.Cluster/Serialization/ReliableDeliverySerializer.cs
index 55fb8933b45..f8f437f8043 100644
--- a/src/core/Akka.Cluster/Serialization/ReliableDeliverySerializer.cs
+++ b/src/core/Akka.Cluster/Serialization/ReliableDeliverySerializer.cs
@@ -46,6 +46,9 @@ public ReliableDeliverySerializer(ExtendedActorSystem system) : base(system)
         _payloadSupport = new WrappedPayloadSupport(system);
     }
 
+    /// <inheritdoc />
+    public override int Identifier => 36;
+
     public override byte[] ToBinary(object obj)
     {
         switch (obj)
diff --git a/src/core/Akka.Persistence/Serialization/PersistenceMessageSerializer.cs b/src/core/Akka.Persistence/Serialization/PersistenceMessageSerializer.cs
index 36b2cea7af5..f88846ef94e 100644
--- a/src/core/Akka.Persistence/Serialization/PersistenceMessageSerializer.cs
+++ b/src/core/Akka.Persistence/Serialization/PersistenceMessageSerializer.cs
@@ -25,6 +25,9 @@ public PersistenceMessageSerializer(ExtendedActorSystem system) : base(system)
         {
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 7;
+
         public override bool IncludeManifest { get; } = true;
 
         public override byte[] ToBinary(object obj)
diff --git a/src/core/Akka.Persistence/Serialization/PersistenceSnapshotSerializer.cs b/src/core/Akka.Persistence/Serialization/PersistenceSnapshotSerializer.cs
index e2e06978a99..5d4e074d328 100644
--- a/src/core/Akka.Persistence/Serialization/PersistenceSnapshotSerializer.cs
+++ b/src/core/Akka.Persistence/Serialization/PersistenceSnapshotSerializer.cs
@@ -20,6 +20,12 @@ public PersistenceSnapshotSerializer(ExtendedActorSystem system) : base(system)
             IncludeManifest = true;
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(PersistenceSnapshotSerializer) ? 8 : base.Identifier;
+
         public override bool IncludeManifest { get; }
 
         public override byte[] ToBinary(object obj)
diff --git a/src/core/Akka.Remote/Serialization/DaemonMsgCreateSerializer.cs b/src/core/Akka.Remote/Serialization/DaemonMsgCreateSerializer.cs
index ab7f54cd440..66aa3fc1047 100644
--- a/src/core/Akka.Remote/Serialization/DaemonMsgCreateSerializer.cs
+++ b/src/core/Akka.Remote/Serialization/DaemonMsgCreateSerializer.cs
@@ -30,6 +30,12 @@ public DaemonMsgCreateSerializer(ExtendedActorSystem system) : base(system)
         {
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(DaemonMsgCreateSerializer) ? 3 : base.Identifier;
+
         /// <inheritdoc />
         public override bool IncludeManifest => false;
 
diff --git a/src/core/Akka.Remote/Serialization/MessageContainerSerializer.cs b/src/core/Akka.Remote/Serialization/MessageContainerSerializer.cs
index 6d08d18950e..b18753a9628 100644
--- a/src/core/Akka.Remote/Serialization/MessageContainerSerializer.cs
+++ b/src/core/Akka.Remote/Serialization/MessageContainerSerializer.cs
@@ -31,6 +31,12 @@ public MessageContainerSerializer(ExtendedActorSystem system) : base(system)
             _payloadSupport = new WrappedPayloadSupport(system);
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(MessageContainerSerializer) ? 6 : base.Identifier;
+
         /// <inheritdoc />
         public override bool IncludeManifest => false;
 
diff --git a/src/core/Akka.Remote/Serialization/MiscMessageSerializer.cs b/src/core/Akka.Remote/Serialization/MiscMessageSerializer.cs
index d88a9473eb1..4ada5289274 100644
--- a/src/core/Akka.Remote/Serialization/MiscMessageSerializer.cs
+++ b/src/core/Akka.Remote/Serialization/MiscMessageSerializer.cs
@@ -61,6 +61,9 @@ public MiscMessageSerializer(ExtendedActorSystem system) : base(system)
             _exceptionSupport = new ExceptionSupport(system);
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 16;
+
         /// <inheritdoc />
         public override byte[] ToBinary(object obj)
         {
diff --git a/src/core/Akka.Remote/Serialization/PrimitiveSerializers.cs b/src/core/Akka.Remote/Serialization/PrimitiveSerializers.cs
index a3badc9f27c..e083063b434 100644
--- a/src/core/Akka.Remote/Serialization/PrimitiveSerializers.cs
+++ b/src/core/Akka.Remote/Serialization/PrimitiveSerializers.cs
@@ -45,6 +45,9 @@ public PrimitiveSerializers(ExtendedActorSystem system, Config config) : base(sy
             _useLegacyBehavior = config.GetBoolean("use-legacy-behavior");
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 17;
+
         /// <inheritdoc />
         public override byte[] ToBinary(object obj)
         {
diff --git a/src/core/Akka.Remote/Serialization/ProtobufSerializer.cs b/src/core/Akka.Remote/Serialization/ProtobufSerializer.cs
index f2956721185..763b7bb0e01 100644
--- a/src/core/Akka.Remote/Serialization/ProtobufSerializer.cs
+++ b/src/core/Akka.Remote/Serialization/ProtobufSerializer.cs
@@ -29,6 +29,12 @@ public ProtobufSerializer(ExtendedActorSystem system) : base(system)
         {
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ProtobufSerializer) ? 2 : base.Identifier;
+
         /// <inheritdoc />
         public override bool IncludeManifest => true;
 
diff --git a/src/core/Akka.Remote/Serialization/SystemMessageSerializer.cs b/src/core/Akka.Remote/Serialization/SystemMessageSerializer.cs
index 14f41af3dc0..754db99dee0 100644
--- a/src/core/Akka.Remote/Serialization/SystemMessageSerializer.cs
+++ b/src/core/Akka.Remote/Serialization/SystemMessageSerializer.cs
@@ -33,6 +33,9 @@ public SystemMessageSerializer(ExtendedActorSystem system) : base(system)
             _exceptionSupport = new ExceptionSupport(system);
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 22;
+
         /// <inheritdoc />
         public override bool IncludeManifest { get; } = true; // TODO: should be false
 
diff --git a/src/core/Akka.Streams/Serialization/StreamRefSerializer.cs b/src/core/Akka.Streams/Serialization/StreamRefSerializer.cs
index 44f64c724c6..49b1656555b 100644
--- a/src/core/Akka.Streams/Serialization/StreamRefSerializer.cs
+++ b/src/core/Akka.Streams/Serialization/StreamRefSerializer.cs
@@ -38,6 +38,9 @@ public StreamRefSerializer(ExtendedActorSystem system) : base(system)
             _system = system;
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 30;
+
         public override string Manifest(object o)
         {
             return o switch
diff --git a/src/core/Akka.Tests/Serialization/SerializerSubclassIdentifierSpec.cs b/src/core/Akka.Tests/Serialization/SerializerSubclassIdentifierSpec.cs
new file mode 100644
index 00000000000..be654b3031b
--- /dev/null
+++ b/src/core/Akka.Tests/Serialization/SerializerSubclassIdentifierSpec.cs
@@ -0,0 +1,46 @@
+//-----------------------------------------------------------------------
+// <copyright file="SerializerSubclassIdentifierSpec.cs" company="Akka.NET Project">
+//     Copyright (C) 2009-2025 Lightbend Inc. <http://www.lightbend.com>
+//     Copyright (C) 2013-2025 .NET Foundation <https://github.com/akkadotnet/akka.net>
+// </copyright>
+//-----------------------------------------------------------------------
+
+#nullable enable
+using Akka.Actor;
+using Akka.Configuration;
+using Akka.Serialization;
+using FluentAssertions;
+using Xunit;
+
+namespace Akka.Tests.Serialization
+{
+    /// <summary>
+    /// A public, unsealed built-in serializer's <c>Identifier</c> override guards on <c>GetType()</c>, so a user
+    /// subclass registered under its own HOCON id keeps resolving that id from HOCON instead of inheriting the
+    /// built-in's hardcoded constant.
+    /// </summary>
+    public class SerializerSubclassIdentifierSpec
+    {
+        public sealed class MyJsonSerializer : NewtonSoftJsonSerializer
+        {
+            public MyJsonSerializer(ExtendedActorSystem system) : base(system)
+            {
+            }
+        }
+
+        [Fact(DisplayName = "Should_keep_resolving_its_own_HOCON_id_When_a_user_subclasses_a_builtin_serializer")]
+        public void Should_keep_resolving_its_own_HOCON_id_When_a_user_subclasses_a_builtin_serializer()
+        {
+            var config = ConfigurationFactory.ParseString(@"
+                akka.actor.serialization-identifiers {
+                    ""Akka.Tests.Serialization.SerializerSubclassIdentifierSpec+MyJsonSerializer, Akka.Tests"" = 100
+                }");
+
+            using var system = ActorSystem.Create(nameof(SerializerSubclassIdentifierSpec), config);
+            var extendedSystem = (ExtendedActorSystem)system;
+
+            new MyJsonSerializer(extendedSystem).Identifier.Should().Be(100);
+            new NewtonSoftJsonSerializer(extendedSystem).Identifier.Should().Be(1);
+        }
+    }
+}
diff --git a/src/core/Akka/Serialization/ByteArraySerializer.cs b/src/core/Akka/Serialization/ByteArraySerializer.cs
index 577e3bd2137..3e98ca4c654 100644
--- a/src/core/Akka/Serialization/ByteArraySerializer.cs
+++ b/src/core/Akka/Serialization/ByteArraySerializer.cs
@@ -26,6 +26,12 @@ public ByteArraySerializer(ExtendedActorSystem system)
         {
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ByteArraySerializer) ? 4 : base.Identifier;
+
         /// <summary>
         /// Byte arrays preserve their legacy empty manifest for wire compatibility.
         /// </summary>
diff --git a/src/core/Akka/Serialization/NewtonSoftJsonSerializer.cs b/src/core/Akka/Serialization/NewtonSoftJsonSerializer.cs
index 7474e21cad8..f35c8abf7be 100644
--- a/src/core/Akka/Serialization/NewtonSoftJsonSerializer.cs
+++ b/src/core/Akka/Serialization/NewtonSoftJsonSerializer.cs
@@ -238,7 +238,11 @@ public NewtonSoftJsonSerializer(ExtendedActorSystem system, NewtonSoftJsonSerial
                 _surrogateExcludedSerializer.Converters.Remove(surrogateConverter);
         }
 
-
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(NewtonSoftJsonSerializer) ? 1 : base.Identifier;
 
         private static JsonConverter CreateConverter(Type converterType, ExtendedActorSystem actorSystem)
         {