diff --git a/packages/gen/gen_ai_hub/orchestration_v2/models/message.py b/packages/gen/gen_ai_hub/orchestration_v2/models/message.py
index f098c77..5534251 100644
--- a/packages/gen/gen_ai_hub/orchestration_v2/models/message.py
+++ b/packages/gen/gen_ai_hub/orchestration_v2/models/message.py
@@ -59,6 +59,17 @@ class MessageToolCall(BaseModel):
     type: typing.Literal["function"] = "function"
     function: FunctionCall
 
+class ReasoningBlock(BaseModel):
+    """
+    The reasoning content returned by the model.
+
+    Attributes:
+        content: The reasoning content.
+        signature: Signature string for hidden reasoning content.
+    """
+    content: str
+    signature: str
+
 
 class Role(str, Enum):
     """
@@ -182,11 +193,14 @@ class ResponseChatMessage(BaseModel):
         refusal: A string indicating refusal reason.
 
         tool_calls: A list of tool call objects.
+
+        reasoning_content: A list of reasoning content blocks.
     """
     role: Role = Role.ASSISTANT
     content: str
     refusal: Optional[str] = None
     tool_calls: Optional[List[MessageToolCall]] = None
+    reasoning_content: Optional[List[ReasoningBlock]] = None
 
 ChatMessage = Union[SystemMessage, UserMessage, AssistantMessage, ToolChatMessage, DeveloperChatMessage,
 ResponseChatMessage]
diff --git a/packages/gen/tests/orchestration_v2/test_message_v2.py b/packages/gen/tests/orchestration_v2/test_message_v2.py
new file mode 100644
index 0000000..f4744e7
--- /dev/null
+++ b/packages/gen/tests/orchestration_v2/test_message_v2.py
@@ -0,0 +1,22 @@
+import unittest
+
+from gen_ai_hub.orchestration_v2.models.message import (
+    ReasoningBlock,
+    ResponseChatMessage,
+)
+
+
+class TestResponseChatMessageValidation(unittest.TestCase):
+
+    def test_reasoning_content_deserialized_from_dict(self):
+        msg = ResponseChatMessage.model_validate({
+            "role": "assistant",
+            "content": "Hello",
+            "reasoning_content": [{"content": "I think...", "signature": "sig123"}],
+        })
+        assert msg.reasoning_content is not None
+        self.assertIsInstance(msg.reasoning_content[0], ReasoningBlock)
+
+    def test_reasoning_content_optional(self):
+        msg = ResponseChatMessage.model_validate({"role": "assistant", "content": "Hello"})
+        self.assertIsNone(msg.reasoning_content)