.NET: Fix JsonWireSerializedValue hash code contract

dotnet/src/Microsoft.Agents.AI.Workflows/Checkpointing/JsonWireSerializedValue.cs

@@ -58,6 +58,9 @@ public override bool Equals(object? obj)
 
     public override int GetHashCode()
     {
-        return this.Data.GetHashCode();
+        // JsonElement does not provide a structural hash code. ValueKind is necessarily equal
+        // whenever DeepEquals returns true, preserving the equality contract without recursively
+        // reimplementing JsonElement.DeepEquals semantics.
+        return this.Data.ValueKind.GetHashCode();
     }
 }

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/JsonSerializationTests.cs

@@ -33,6 +33,24 @@
 
     private static EdgeId TakeEdgeId() => new(Interlocked.Increment(ref s_nextEdgeId));
 
+    [Fact]
+    public void Test_JsonWireSerializedValue_EqualValuesHaveEqualHashCodes()
+    {
+        // Arrange
+        JsonMarshaller marshaller = new();
+        using JsonDocument firstDocument = JsonDocument.Parse("""{"a":1,"b":[true,null]}""");
+        using JsonDocument secondDocument = JsonDocument.Parse("""{"a":1,"b":[true,null]}""");
+        JsonWireSerializedValue first = new(marshaller, firstDocument.RootElement);
+        JsonWireSerializedValue second = new(marshaller, secondDocument.RootElement);
+
+        // Act
+        bool areEqual = first.Equals(second);
+
+        // Assert
+        areEqual.Should().BeTrue();
+        first.GetHashCode().Should().Be(second.GetHashCode());
+    }
+
     internal static T RunJsonRoundtrip<T>(T value, JsonSerializerOptions? externalOptions = null, Expression<Func<T, bool>>? predicate = null)
     {
         JsonMarshaller marshaller = new(externalOptions);