fix(inbound-api): endpoint filter hot-reads MaxRequestBodyBytes via IOptionsMonitor

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.InboundAPI/InboundApiEndpointFilter.cs

@@ -24,17 +24,17 @@ namespace ZB.MOM.WW.ScadaBridge.InboundAPI;
 public sealed class InboundApiEndpointFilter : IEndpointFilter
 {
     private readonly ILogger<InboundApiEndpointFilter> _logger;
-    private readonly InboundApiOptions _options;
+    private readonly IOptionsMonitor<InboundApiOptions> _options;
 
     /// <summary>Initializes a new <see cref="InboundApiEndpointFilter"/> with the given logger and options.</summary>
     /// <param name="logger">Logger for request rejection diagnostics.</param>
-    /// <param name="options">Inbound API options including the maximum request body size.</param>
+    /// <param name="options">Live-reloadable inbound API options, read per-request.</param>
     public InboundApiEndpointFilter(
         ILogger<InboundApiEndpointFilter> logger,
-        IOptions<InboundApiOptions> options)
+        IOptionsMonitor<InboundApiOptions> options)
     {
         _logger = logger;
-        _options = options.Value;
+        _options = options;
     }
 
     /// <summary>Applies active-node gating and request body size checks before delegating to the next filter or handler.</summary>
@@ -63,7 +63,7 @@ public sealed class InboundApiEndpointFilter : IEndpointFilter
         // Cap the request body size. Reject an over-limit body up
         // front via Content-Length; also lower the per-request max body size so a
         // chunked/unknown-length stream is cut off by Kestrel as it is read.
-        var maxBytes = _options.MaxRequestBodyBytes;
+        var maxBytes = _options.CurrentValue.MaxRequestBodyBytes;
         if (httpContext.Request.ContentLength is { } declaredLength && declaredLength > maxBytes)
         {
             _logger.LogWarning(

tests/ZB.MOM.WW.ScadaBridge.InboundAPI.Tests/EndpointGatingTests.cs

@@ -15,7 +15,7 @@ public class EndpointGatingTests
 {
     private static InboundApiEndpointFilter CreateFilter(InboundApiOptions? options = null) =>
         new(NullLogger<InboundApiEndpointFilter>.Instance,
-            Options.Create(options ?? new InboundApiOptions()));
+            new TestOptionsMonitor<InboundApiOptions>(options ?? new InboundApiOptions()));
 
     private static (DefaultHttpContext ctx, DefaultEndpointFilterInvocationContext invocation)
         BuildInvocation(bool? activeNode, long? contentLength)
@@ -144,4 +144,37 @@ public class EndpointGatingTests
         public bool IsReadOnly => false;
         public long? MaxRequestBodySize { get; set; }
     }
+
+    // --- InboundAPI hot-reload: options must be re-read per request, not cached at ctor time ---
+
+    [Fact]
+    public async Task BodySizeCap_HotReloads_WithoutRestart()
+    {
+        var monitor = new TestOptionsMonitor<InboundApiOptions>(new InboundApiOptions { MaxRequestBodyBytes = 10 });
+        var filter = new InboundApiEndpointFilter(NullLogger<InboundApiEndpointFilter>.Instance, monitor);
+
+        var (_, firstInvocation) = BuildInvocation(activeNode: true, contentLength: 20);
+        var firstNext = NextSentinel(out var firstHandlerRan);
+        var firstResult = await filter.InvokeAsync(firstInvocation, firstNext);
+
+        Assert.False(firstHandlerRan());
+        var firstStatus = Assert.IsAssignableFrom<IStatusCodeHttpResult>(firstResult);
+        Assert.Equal(StatusCodes.Status413PayloadTooLarge, firstStatus.StatusCode);
+
+        monitor.CurrentValue = new InboundApiOptions { MaxRequestBodyBytes = 1024 * 1024 };
+
+        var (_, secondInvocation) = BuildInvocation(activeNode: true, contentLength: 20);
+        var secondNext = NextSentinel(out var secondHandlerRan);
+        await filter.InvokeAsync(secondInvocation, secondNext);
+
+        Assert.True(secondHandlerRan());
+    }
+
+    private sealed class TestOptionsMonitor<T> : IOptionsMonitor<T>
+    {
+        public TestOptionsMonitor(T currentValue) => CurrentValue = currentValue;
+        public T CurrentValue { get; set; }
+        public T Get(string? name) => CurrentValue;
+        public IDisposable? OnChange(Action<T, string?> listener) => null;
+    }
 }