Fix NATS JetStream native scheduled send (err 10190) and add configurable schedule-subject suffix.

docs/guide/messaging/transports/nats.md

@@ -348,10 +348,29 @@ opts.UseNats("nats://localhost:4222")
 
 When conditions are met, scheduled messages use NATS headers:
 - `Nats-Schedule: @at <RFC3339 timestamp>`
-- `Nats-Schedule-Target: <subject>`
+- `Nats-Schedule-Target: <destination subject>`
 
 The transport automatically detects server version at startup.
 
+NATS requires the scheduling (control) message to be published to a subject that is **different** from
+`Nats-Schedule-Target` — publishing both to the same subject is rejected with
+`message schedules target is invalid` (err 10190). Wolverine therefore publishes the control message to a
+derived **schedule subject** — the destination subject plus a suffix (default `.scheduled`, e.g.
+`orders.created.scheduled`) — while `Nats-Schedule-Target` stays the real destination
+(`orders.created`). At the scheduled time the server materializes a new message onto the target subject,
+where your listener's consumer receives it; the control message itself is never delivered to consumers.
+
+Both the schedule subject and the target must be covered by the **same stream**, so use a wildcard subject
+filter such as `orders.>` (a single-token `*` filter or an exact-subject filter will **not** cover
+`<subject>.scheduled`). Override the suffix per publishing endpoint when needed:
+
+```csharp
+opts.PublishMessage<OrderCreated>()
+    .ToNatsSubject("orders.created")
+    .UseJetStream("ORDERS")
+    .UseScheduleSubjectSuffix(".deferred");
+```
+
 ### Fallback Behavior
 
 When native scheduled send is not available (server < 2.12 or stream not configured), Wolverine falls back to its database-backed scheduled message persistence.

src/Transports/NATS/Wolverine.Nats.Tests/NatsScheduleSubjectSuffixTests.cs

@@ -0,0 +1,38 @@
+using Shouldly;
+using Wolverine.Nats.Configuration;
+using Wolverine.Nats.Internal;
+using Xunit;
+
+namespace Wolverine.Nats.Tests;
+
+public class NatsScheduleSubjectSuffixTests
+{
+    private static NatsEndpoint EndpointFor(string subject = "orders.created")
+    {
+        var transport = new NatsTransport();
+        return (NatsEndpoint)transport.GetOrCreateEndpoint(NatsEndpointUri.Subject(subject));
+    }
+
+    [Fact]
+    public void default_suffix_is_scheduled()
+    {
+        EndpointFor().ScheduleSubjectSuffix.ShouldBe(".scheduled");
+    }
+
+    [Theory]
+    [InlineData(".scheduled")]
+    [InlineData(".override-scheduled")]
+    [InlineData(".control")]
+    public void use_schedule_subject_suffix_round_trips_to_endpoint(string suffix)
+    {
+        var endpoint = EndpointFor();
+        var configuration = new NatsSubscriberConfiguration(endpoint);
+
+        configuration.UseScheduleSubjectSuffix(suffix);
+        // Callbacks are buffered in the IDelayedEndpointConfiguration base; Apply() mirrors what the
+        // runtime does at endpoint compile time.
+        ((Wolverine.Configuration.IDelayedEndpointConfiguration)configuration).Apply();
+
+        endpoint.ScheduleSubjectSuffix.ShouldBe(suffix);
+    }
+}

src/Transports/NATS/Wolverine.Nats.Tests/ScheduledMessageDeliveryTests.cs

@@ -0,0 +1,119 @@
+using FluentAssertions;
+using JasperFx.Core;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Wolverine.Nats.Internal;
+using Wolverine.Runtime;
+using Wolverine.Tracking;
+using Xunit;
+
+namespace Wolverine.Nats.Tests;
+
+/// <summary>
+/// Reproduces the NATS JetStream native scheduled-delivery failure (err 10190). Unlike the compliance
+/// <c>schedule_send</c> test, the publishing endpoint here uses <c>.UseJetStream(stream)</c> — that is what
+/// engages the native scheduled-send path; without it Wolverine falls back to durable scheduling and the
+/// bug is never exercised.
+/// </summary>
+[Collection("NATS Integration Tests")]
+[Trait("Category", "Integration")]
+public class ScheduledMessageDeliveryTests : IAsyncLifetime
+{
+    private static int _counter;
+    private IHost? _sender;
+    private IHost? _receiver;
+    private string _receiverSubject = "";
+
+    public async Task InitializeAsync()
+    {
+        var natsUrl = Environment.GetEnvironmentVariable("NATS_URL") ?? "nats://localhost:4222";
+
+        var n = ++_counter;
+        var streamName = $"SCHEDULED_{n}";
+        _receiverSubject = $"test.scheduled.{n}.receiver";
+        var streamSubjects = $"test.scheduled.{n}.>";
+
+        _sender = await Host.CreateDefaultBuilder()
+            .UseWolverine(opts =>
+            {
+                opts.ServiceName = "ScheduleSender";
+                opts.UseNats(natsUrl)
+                    .AutoProvision()
+                    .UseJetStream(js => js.MaxDeliver = 5)
+                    .DefineWorkQueueStream(streamName, s => s.EnableScheduledDelivery(), streamSubjects);
+
+                // .UseJetStream on the PUBLISHING endpoint is what forces the native scheduled-send path.
+                opts.PublishMessage<ScheduledPing>()
+                    .ToNatsSubject(_receiverSubject)
+                    .UseJetStream(streamName);
+            })
+            .StartAsync();
+
+        _receiver = await Host.CreateDefaultBuilder()
+            .UseWolverine(opts =>
+            {
+                opts.ServiceName = "ScheduleReceiver";
+                opts.UseNats(natsUrl)
+                    .AutoProvision()
+                    .UseJetStream(js => js.MaxDeliver = 5)
+                    .DefineWorkQueueStream(streamName, s => s.EnableScheduledDelivery(), streamSubjects);
+
+                opts.ListenToNatsSubject(_receiverSubject)
+                    .Named("receiver")
+                    .UseJetStream(streamName, $"receiver-consumer-{n}");
+            })
+            .StartAsync();
+    }
+
+    public async Task DisposeAsync()
+    {
+        if (_sender != null)
+        {
+            await _sender.StopAsync();
+        }
+
+        if (_receiver != null)
+        {
+            await _receiver.StopAsync();
+        }
+
+        _sender?.Dispose();
+        _receiver?.Dispose();
+    }
+
+    [Fact]
+    public async Task schedule_send_over_native_jetstream_scheduling()
+    {
+        // Native scheduled delivery requires NATS Server 2.12+. Skip on older images rather than fail.
+        var runtime = _sender!.Services.GetRequiredService<IWolverineRuntime>();
+        var transport = runtime.Options.Transports.GetOrCreate<NatsTransport>();
+        if (!transport.ServerSupportsScheduledSend)
+        {
+            return;
+        }
+
+        // Guard: confirm the native path is engaged, not the durable-scheduling fallback that would mask the bug.
+        var agent = runtime.Endpoints.GetOrBuildSendingAgent(new Uri($"nats://subject/{_receiverSubject}"));
+        agent.SupportsNativeScheduledSend.Should().BeTrue();
+
+        var message = new ScheduledPing(Guid.NewGuid(), "scheduled");
+
+        var session = await _sender
+            .TrackActivity()
+            .AlsoTrack(_receiver)
+            .Timeout(30.Seconds())
+            .WaitForMessageToBeReceivedAt<ScheduledPing>(_receiver!)
+            .ExecuteAndWaitAsync(c => c.ScheduleAsync(message, 5.Seconds()).AsTask());
+
+        session.Received.SingleMessage<ScheduledPing>().Should().BeEquivalentTo(message);
+    }
+}
+
+public record ScheduledPing(Guid Id, string Text);
+
+public class ScheduledPingHandler
+{
+    public void Handle(ScheduledPing message)
+    {
+    }
+}

src/Transports/NATS/Wolverine.Nats/Configuration/NatsSubscriberConfiguration.cs

@@ -25,4 +25,14 @@ public NatsSubscriberConfiguration UseJetStream(string? streamName = null)
 
         return this;
     }
+
+    /// <summary>
+    /// Override the suffix used to derive the NATS JetStream scheduling subject for native scheduled sends
+    /// (default <c>.scheduled</c>). The derived subject must stay covered by the destination's stream.
+    /// </summary>
+    public NatsSubscriberConfiguration UseScheduleSubjectSuffix(string suffix)
+    {
+        add(endpoint => endpoint.ScheduleSubjectSuffix = suffix);
+        return this;
+    }
 }

src/Transports/NATS/Wolverine.Nats/Internal/JetStreamPublisher.cs

@@ -13,11 +13,16 @@ internal class JetStreamPublisher : INatsPublisher
     private readonly NatsConnection _connection;
     private readonly INatsJSContext _jetStreamContext;
     private readonly ILogger<NatsEndpoint> _logger;
+    private readonly string _scheduleSubjectSuffix;
 
-    public JetStreamPublisher(NatsConnection connection, ILogger<NatsEndpoint> logger)
+    public JetStreamPublisher(NatsConnection connection, 
+        ILogger<NatsEndpoint> logger,
+        string scheduleSubjectSuffix = ".scheduled")
     {
         _connection = connection;
         _logger = logger;
+        // An empty suffix would make the schedule subject equal the target and re-trigger err 10190.
+        _scheduleSubjectSuffix = string.IsNullOrWhiteSpace(scheduleSubjectSuffix) ? ".scheduled" : scheduleSubjectSuffix;
         _jetStreamContext = connection.CreateJetStreamContext();
     }
 
@@ -70,28 +75,33 @@ await _connection.PublishAsync(
         }
         else
         {
-            // Check if this is a scheduled message
+            var publishSubject = subject;
+
             if (envelope.ScheduledTime.HasValue)
             {
-                // Add NATS scheduling headers
-                // Format: @at <RFC3339 timestamp>
+                // NATS rejects a scheduled publish whose subject equals Nats-Schedule-Target ("message
+                // schedules target is invalid", err 10190). So the target stays the real destination
+                // (where the consumer listens and the server materializes the message), and the control
+                // message goes to a derived subject that must still be covered by the same stream.
                 var scheduledTime = envelope.ScheduledTime.Value.ToUniversalTime();
                 headers["Nats-Schedule"] = $"@at {scheduledTime:O}";
                 headers["Nats-Schedule-Target"] = subject;
-
+                publishSubject = subject + _scheduleSubjectSuffix;
+
                 if (_logger.IsEnabled(LogLevel.Debug))
                 {
                     _logger.LogDebug(
-                        "Scheduling message {MessageId} for delivery at {ScheduledTime} to {Subject}",
+                        "Scheduling message {MessageId} for delivery at {ScheduledTime} to {Target} via schedule subject {ScheduleSubject}",
                         envelope.Id,
                         scheduledTime,
-                        subject
+                        subject,
+                        publishSubject
                     );
                 }
             }
-            
+
             var ack = await _jetStreamContext.PublishAsync(
-                subject,
+                publishSubject,
                 data,
                 headers: headers,
                 cancellationToken: cancellation

src/Transports/NATS/Wolverine.Nats/Internal/NatsEndpoint.cs

@@ -47,6 +47,13 @@ public NatsEndpoint(string subject, NatsTransport transport, EndpointRole role)
     public string? DeadLetterSubject { get; set; }
     public int MaxDeliveryAttempts { get; set; } = 5;
 
+    /// <summary>
+    /// Suffix appended to the destination subject to form the NATS JetStream scheduling subject for native
+    /// scheduled sends. Must keep the schedule subject covered by the stream (e.g. a <c>prefix.&gt;</c>
+    /// filter covers <c>{subject}.scheduled</c>). Defaults to <c>.scheduled</c>.
+    /// </summary>
+    public string ScheduleSubjectSuffix { get; set; } = ".scheduled";
+
     /// <summary>
     /// Per-endpoint override for the JetStream consumer's <c>DeliverPolicy</c>.
     /// When non-null this wins over

src/Transports/NATS/Wolverine.Nats/Internal/NatsSender.cs

@@ -42,7 +42,7 @@ bool supportsNativeScheduledSend
     )
     {
         INatsPublisher publisher = useJetStream
-            ? new JetStreamPublisher(connection, logger)
+            ? new JetStreamPublisher(connection, logger, endpoint.ScheduleSubjectSuffix)
             : new CoreNatsPublisher(connection, logger);
 
         return new NatsSender(endpoint, publisher, logger, mapper, cancellation, supportsNativeScheduledSend);