diff --git a/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptions.cs b/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptions.cs
index 38648373f..0a41e9847 100644
--- a/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptions.cs
+++ b/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptions.cs
@@ -52,18 +52,21 @@ public sealed class DaprActorsOptions
 
     /// <summary>
     /// Gets or sets the idle timeout for actor activations.
+    /// <see langword="null"/> leaves the value unset so the Dapr runtime default applies.
     /// </summary>
-    public TimeSpan ActorIdleTimeout { get; set; } = TimeSpan.FromMinutes(60);
+    public TimeSpan? ActorIdleTimeout { get; set; }
 
     /// <summary>
     /// Gets or sets the timeout used when draining ongoing actor calls.
+    /// <see langword="null"/> leaves the value unset so the Dapr runtime default applies.
     /// </summary>
-    public TimeSpan DrainOngoingCallTimeout { get; private set; } = TimeSpan.FromSeconds(30);
+    public TimeSpan? DrainOngoingCallTimeout { get; set; }
 
     /// <summary>
     /// Gets or sets the timeout used when draining rebalanced actors.
+    /// <see langword="null"/> leaves the value unset so the Dapr runtime default applies.
     /// </summary>
-    public TimeSpan DrainRebalancedActorsTimeout
+    public TimeSpan? DrainRebalancedActorsTimeout
     {
         get => DrainOngoingCallTimeout;
         set => DrainOngoingCallTimeout = value;
@@ -71,13 +74,15 @@ public TimeSpan DrainRebalancedActorsTimeout
 
     /// <summary>
     /// Gets or sets a value indicating whether rebalanced actors drain in-flight calls.
+    /// <see langword="null"/> leaves the value unset so the Dapr runtime default applies.
     /// </summary>
-    public bool DrainRebalancedActors { get; set; } = true;
+    public bool? DrainRebalancedActors { get; set; }
 
     /// <summary>
     /// Gets or sets a value indicating whether reentrant actor calls are allowed.
+    /// <see langword="null"/> leaves the value unset so the Dapr runtime default applies.
     /// </summary>
-    public bool EnableReentrancy { get; set; }
+    public bool? EnableReentrancy { get; set; }
 
     /// <summary>
     /// Gets or sets a value indicating whether the sidecar (gRPC) transport is used for actor state,
@@ -90,8 +95,9 @@ public TimeSpan DrainRebalancedActorsTimeout
 
     /// <summary>
     /// Gets or sets the maximum reentrant call depth when reentrancy is enabled.
+    /// <see langword="null"/> leaves the value unset so the Dapr runtime default applies.
     /// </summary>
-    public int MaxReentrantDepth { get; set; } = 32;
+    public int? MaxReentrantDepth { get; set; }
 
     internal void CopyFrom(DaprActorsOptions source)
     {
diff --git a/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptionsValidator.cs b/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptionsValidator.cs
index 0d8e4a3c1..3c8b2d34b 100644
--- a/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptionsValidator.cs
+++ b/src/Dapr.Actors.Next.Abstractions/Options/DaprActorsOptionsValidator.cs
@@ -26,10 +26,10 @@ public ValidateOptionsResult Validate(string? name, DaprActorsOptions options)
         List<string>? failures = null;
 
         AddFailureIf(options.DefaultContractVersion <= 0, "DefaultContractVersion must be greater than zero.", ref failures);
-        AddFailureIf(options.ActorIdleTimeout <= TimeSpan.Zero, "ActorIdleTimeout must be greater than zero.", ref failures);
-        AddFailureIf(options.DrainOngoingCallTimeout <= TimeSpan.Zero, "DrainOngoingCallTimeout must be greater than zero.", ref failures);
-        AddFailureIf(options.DrainRebalancedActorsTimeout <= TimeSpan.Zero, "DrainRebalancedActorsTimeout must be greater than zero.", ref failures);
-        AddFailureIf(options.MaxReentrantDepth <= 0, "MaxReentrantDepth must be greater than zero.", ref failures);
+        AddFailureIf(options.ActorIdleTimeout is { } globalIdleTimeout && globalIdleTimeout <= TimeSpan.Zero, "ActorIdleTimeout must be greater than zero.", ref failures);
+        AddFailureIf(options.DrainOngoingCallTimeout is { } globalDrainTimeout && globalDrainTimeout <= TimeSpan.Zero, "DrainOngoingCallTimeout must be greater than zero.", ref failures);
+        AddFailureIf(options.DrainRebalancedActorsTimeout is { } globalDrainRebalancedTimeout && globalDrainRebalancedTimeout <= TimeSpan.Zero, "DrainRebalancedActorsTimeout must be greater than zero.", ref failures);
+        AddFailureIf(options.MaxReentrantDepth is { } globalMaxDepth && globalMaxDepth <= 0, "MaxReentrantDepth must be greater than zero.", ref failures);
 
         foreach (var registration in options.Actors.Registrations)
         {
diff --git a/src/Dapr.Actors.Next.Core/Transport/DaprActorEventsTransport.cs b/src/Dapr.Actors.Next.Core/Transport/DaprActorEventsTransport.cs
index ba8ab3b2a..281b1294b 100644
--- a/src/Dapr.Actors.Next.Core/Transport/DaprActorEventsTransport.cs
+++ b/src/Dapr.Actors.Next.Core/Transport/DaprActorEventsTransport.cs
@@ -240,17 +240,38 @@ private static P.SubscribeActorEventsRequestInitialAlpha1 CreateInitialRequest(S
                 return request;
             }
 
-            var entityConfig = new P.ActorEntityConfig
+            // Only assign fields the app configured; unset fields keep their
+            // Dapr runtime defaults.
+            var entityConfig = new P.ActorEntityConfig();
+
+            if (config.ActorIdleTimeout is { } idleTimeout)
             {
-                ActorIdleTimeout = Duration.FromTimeSpan(config.ActorIdleTimeout),
-                DrainOngoingCallTimeout = Duration.FromTimeSpan(config.DrainOngoingCallTimeout),
-                DrainRebalancedActors = config.DrainRebalancedActors,
-                Reentrancy = new P.ActorReentrancyConfig
+                entityConfig.ActorIdleTimeout = Duration.FromTimeSpan(idleTimeout);
+            }
+
+            if (config.DrainOngoingCallTimeout is { } drainTimeout)
+            {
+                entityConfig.DrainOngoingCallTimeout = Duration.FromTimeSpan(drainTimeout);
+            }
+
+            if (config.DrainRebalancedActors is { } drainRebalanced)
+            {
+                entityConfig.DrainRebalancedActors = drainRebalanced;
+            }
+
+            if (config.EnableReentrancy is not null || config.MaxReentrantDepth is not null)
+            {
+                var reentrancy = new P.ActorReentrancyConfig
                 {
-                    Enabled = config.EnableReentrancy,
-                    MaxStackDepth = config.MaxReentrantDepth,
-                },
-            };
+                    Enabled = config.EnableReentrancy ?? false,
+                };
+                if (config.MaxReentrantDepth is { } maxDepth)
+                {
+                    reentrancy.MaxStackDepth = maxDepth;
+                }
+                entityConfig.Reentrancy = reentrancy;
+            }
+
             entityConfig.Entities.Add(request.Entities);
             request.EntitiesConfig.Add(entityConfig);
             return request;
diff --git a/src/Dapr.Actors.Next.Core/Transport/SubscribeActorEventsResponse.cs b/src/Dapr.Actors.Next.Core/Transport/SubscribeActorEventsResponse.cs
index 5561bbabe..dd3186b0e 100644
--- a/src/Dapr.Actors.Next.Core/Transport/SubscribeActorEventsResponse.cs
+++ b/src/Dapr.Actors.Next.Core/Transport/SubscribeActorEventsResponse.cs
@@ -66,10 +66,12 @@ public static SubscribeActorEventsResponse Failed(string id, string message, uin
 
 /// <summary>
 /// Runtime options advertised with the initial actor event stream registration.
+/// A <see langword="null"/> value leaves that field unset on the wire so the
+/// Dapr runtime default applies.
 /// </summary>
 public sealed record SubscribeActorEventsInitialConfig(
-    TimeSpan ActorIdleTimeout,
-    TimeSpan DrainOngoingCallTimeout,
-    bool DrainRebalancedActors,
-    bool EnableReentrancy,
-    int MaxReentrantDepth);
+    TimeSpan? ActorIdleTimeout,
+    TimeSpan? DrainOngoingCallTimeout,
+    bool? DrainRebalancedActors,
+    bool? EnableReentrancy,
+    int? MaxReentrantDepth);
diff --git a/test/Dapr.Actors.Next.Abstractions.Test/OptionsTests.cs b/test/Dapr.Actors.Next.Abstractions.Test/OptionsTests.cs
index 519606d17..dbcf84504 100644
--- a/test/Dapr.Actors.Next.Abstractions.Test/OptionsTests.cs
+++ b/test/Dapr.Actors.Next.Abstractions.Test/OptionsTests.cs
@@ -146,6 +146,21 @@ public void RegisterActor_NullLiteral_ResolvesToNameOverload()
         Assert.Null(registration.TypeOptions);
     }
 
+    [MinimumDaprRuntimeFact("1.18")]
+    public void Options_DrainRebalancedActorsTimeout_AliasesDrainOngoingCallTimeout()
+    {
+        var options = new DaprActorsOptions();
+        Assert.Null(options.DrainOngoingCallTimeout);
+        Assert.Null(options.DrainRebalancedActorsTimeout);
+
+        options.DrainRebalancedActorsTimeout = TimeSpan.FromSeconds(7);
+        Assert.Equal(TimeSpan.FromSeconds(7), options.DrainOngoingCallTimeout);
+        Assert.Equal(TimeSpan.FromSeconds(7), options.DrainRebalancedActorsTimeout);
+
+        options.DrainOngoingCallTimeout = null;
+        Assert.Null(options.DrainRebalancedActorsTimeout);
+    }
+
     [MinimumDaprRuntimeFact("1.18")]
     public void TypeOptions_DrainRebalancedActorsTimeout_AliasesDrainOngoingCallTimeout()
     {
diff --git a/test/Dapr.Actors.Next.Core.Test/CoreRuntimeTests.cs b/test/Dapr.Actors.Next.Core.Test/CoreRuntimeTests.cs
index 90d38812f..9bd6a9094 100644
--- a/test/Dapr.Actors.Next.Core.Test/CoreRuntimeTests.cs
+++ b/test/Dapr.Actors.Next.Core.Test/CoreRuntimeTests.cs
@@ -117,11 +117,11 @@ public async Task Stream_advertises_global_defaults_in_initial_config()
 
         var config = advertisement.InitialConfig;
         Assert.NotNull(config);
-        Assert.Equal(TimeSpan.FromMinutes(60), config!.ActorIdleTimeout);
-        Assert.Equal(TimeSpan.FromSeconds(30), config.DrainOngoingCallTimeout);
-        Assert.True(config.DrainRebalancedActors);
-        Assert.False(config.EnableReentrancy);
-        Assert.Equal(32, config.MaxReentrantDepth);
+        Assert.Null(config!.ActorIdleTimeout);
+        Assert.Null(config.DrainOngoingCallTimeout);
+        Assert.Null(config.DrainRebalancedActors);
+        Assert.Null(config.EnableReentrancy);
+        Assert.Null(config.MaxReentrantDepth);
     }
 
     [MinimumDaprRuntimeFact("1.18")]
@@ -151,17 +151,17 @@ public async Task Stream_advertises_merged_type_options_per_type()
         var overridden = advertisements["Counter"].InitialConfig;
         Assert.NotNull(overridden);
         Assert.Equal(TimeSpan.FromMinutes(2), overridden!.ActorIdleTimeout);
-        Assert.Equal(TimeSpan.FromSeconds(30), overridden.DrainOngoingCallTimeout);
-        Assert.True(overridden.DrainRebalancedActors);
+        Assert.Null(overridden.DrainOngoingCallTimeout);
+        Assert.Null(overridden.DrainRebalancedActors);
         Assert.True(overridden.EnableReentrancy);
         Assert.Equal(8, overridden.MaxReentrantDepth);
 
         var inherited = advertisements["OtherCounter"].InitialConfig;
         Assert.NotNull(inherited);
         Assert.Equal(TimeSpan.FromMinutes(10), inherited!.ActorIdleTimeout);
-        Assert.Equal(TimeSpan.FromSeconds(30), inherited.DrainOngoingCallTimeout);
-        Assert.True(inherited.DrainRebalancedActors);
-        Assert.False(inherited.EnableReentrancy);
+        Assert.Null(inherited.DrainOngoingCallTimeout);
+        Assert.Null(inherited.DrainRebalancedActors);
+        Assert.Null(inherited.EnableReentrancy);
         Assert.Equal(8, inherited.MaxReentrantDepth);
     }
 
@@ -193,7 +193,7 @@ public async Task Type_options_override_registration_full_options()
         Assert.Equal(TimeSpan.FromMinutes(1), merged!.ActorIdleTimeout);
         Assert.Equal(TimeSpan.FromSeconds(7), merged.DrainOngoingCallTimeout);
         Assert.False(merged.DrainRebalancedActors);
-        Assert.False(merged.EnableReentrancy);
+        Assert.Null(merged.EnableReentrancy);
         Assert.Equal(3, merged.MaxReentrantDepth);
     }
 
diff --git a/test/Dapr.Actors.Next.Core.Test/GeneratedActorEventsTransportTests.cs b/test/Dapr.Actors.Next.Core.Test/GeneratedActorEventsTransportTests.cs
index dfba86cad..be0388aa8 100644
--- a/test/Dapr.Actors.Next.Core.Test/GeneratedActorEventsTransportTests.cs
+++ b/test/Dapr.Actors.Next.Core.Test/GeneratedActorEventsTransportTests.cs
@@ -116,6 +116,32 @@ await stream.WriteAsync(SubscribeActorEventsResponse.RegisteredActors(
         Assert.Equal(7, entityConfig.Reentrancy.MaxStackDepth);
     }
 
+    [MinimumDaprRuntimeFact("1.18")]
+    public async Task Transport_omits_unset_fields_in_initial_config()
+    {
+        var harness = new GeneratedActorEventsHarness();
+        var transport = new DaprActorEventsTransport(harness.Client);
+        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
+
+        await using var stream = await transport.OpenStreamAsync(cts.Token);
+        await stream.WriteAsync(SubscribeActorEventsResponse.RegisteredActors(
+            ["Sparse"],
+            new SubscribeActorEventsInitialConfig(
+                null,
+                TimeSpan.FromSeconds(5),
+                null,
+                null,
+                null)), cts.Token);
+        var initial = await harness.ReceiveAsync(cts.Token);
+
+        var entityConfig = Assert.Single(initial.InitialRequest.EntitiesConfig);
+        Assert.Equal(new[] { "Sparse" }, entityConfig.Entities.ToArray());
+        Assert.Null(entityConfig.ActorIdleTimeout);
+        Assert.Equal(5, entityConfig.DrainOngoingCallTimeout.Seconds);
+        Assert.False(entityConfig.HasDrainRebalancedActors);
+        Assert.Null(entityConfig.Reentrancy);
+    }
+
     [MinimumDaprRuntimeFact("1.18")]
     public async Task Transport_maps_failures_and_non_invoke_callbacks()
     {
diff --git a/test/Dapr.IntegrationTest.Actors.Next/RealSidecarActorTests.cs b/test/Dapr.IntegrationTest.Actors.Next/RealSidecarActorTests.cs
index fd610bdde..cdadfbe44 100644
--- a/test/Dapr.IntegrationTest.Actors.Next/RealSidecarActorTests.cs
+++ b/test/Dapr.IntegrationTest.Actors.Next/RealSidecarActorTests.cs
@@ -164,6 +164,7 @@ private static void ConfigureActorHost(WebApplicationBuilder builder)
         builder.Services.AddDaprActors(options =>
         {
             options.DrainRebalancedActorsTimeout = TimeSpan.FromSeconds(1);
+            options.DrainRebalancedActors = true;
             options.EnableReentrancy = true;
             options.MaxReentrantDepth = 8;
         });