Fix serialization

Author: joseharriaga

codegen/generator/src/OpenAILibraryVisitor.cs

@@ -43,6 +43,7 @@ public class OpenAILibraryVisitor : ScmLibraryVisitor
         ["FunctionCallResponseItem"] = [_readonlyStatusReplacementInfo],
         ["FunctionCallOutputResponseItem"] = [_readonlyStatusReplacementInfo],
         ["MessageResponseItem"] = [_readonlyStatusReplacementInfo],
+        ["ReasoningResponseItem"] = [_readonlyStatusReplacementInfo],
         ["WebSearchCallResponseItem"] = [_readonlyStatusReplacementInfo],
     };
 

src/Generated/Models/Responses/ReasoningResponseItem.Serialization.cs

@@ -36,7 +36,8 @@ protected override void JsonModelWriteCore(Utf8JsonWriter writer, ModelReaderWri
                 writer.WritePropertyName("encrypted_content"u8);
                 writer.WriteStringValue(EncryptedContent);
             }
-            if (_additionalBinaryDataProperties?.ContainsKey("status") != true)
+            // Plugin customization: apply Optional.Is*Defined() check based on type name dictionary lookup
+            if (Optional.IsDefined(Status) && _additionalBinaryDataProperties?.ContainsKey("status") != true)
             {
                 writer.WritePropertyName("status"u8);
                 writer.WriteStringValue(Status.Value.ToSerialString());