diff --git a/basedpyright-code-budget.json b/basedpyright-code-budget.json
index 84313c6a940..a60f1460495 100644
--- a/basedpyright-code-budget.json
+++ b/basedpyright-code-budget.json
@@ -18,7 +18,7 @@
     "limit": 40
   },
   "reportDeprecated": {
-    "limit": 201
+    "limit": 197
   },
   "reportDuplicateImport": {
     "limit": 19
diff --git a/litellm/llms/openai/openai.py b/litellm/llms/openai/openai.py
index 018df2b237c..e2376cf8dd0 100644
--- a/litellm/llms/openai/openai.py
+++ b/litellm/llms/openai/openai.py
@@ -2465,13 +2465,9 @@ class OpenAIAssistantsAPI(BaseLLM):
             **message_data,
         )
 
-        response_obj: OpenAIMessage | None = None
         if getattr(thread_message, "status", None) is None:
             thread_message.status = "completed"
-            response_obj = OpenAIMessage.model_validate(thread_message.dict())
-        else:
-            response_obj = OpenAIMessage.model_validate(thread_message.dict())
-        return response_obj
+        return OpenAIMessage.model_validate(thread_message.model_dump())
 
     # fmt: off
 
@@ -2544,13 +2540,9 @@ class OpenAIAssistantsAPI(BaseLLM):
             **message_data,
         )
 
-        response_obj: OpenAIMessage | None = None
         if getattr(thread_message, "status", None) is None:
             thread_message.status = "completed"
-            response_obj = OpenAIMessage.model_validate(thread_message.dict())
-        else:
-            response_obj = OpenAIMessage.model_validate(thread_message.dict())
-        return response_obj
+        return OpenAIMessage.model_validate(thread_message.model_dump())
 
     async def async_get_messages(
         self,
diff --git a/tests/test_litellm/llms/openai/test_openai_assistants.py b/tests/test_litellm/llms/openai/test_openai_assistants.py
index 36c988749ee..7e679a8a52c 100644
--- a/tests/test_litellm/llms/openai/test_openai_assistants.py
+++ b/tests/test_litellm/llms/openai/test_openai_assistants.py
@@ -3,7 +3,7 @@ import pytest
 from openai import AsyncOpenAI, OpenAI
 
 from litellm.llms.openai.openai import OpenAIAssistantsAPI
-from litellm.types.llms.openai import Thread
+from litellm.types.llms.openai import OpenAIMessage, Thread
 
 _THREAD_PAYLOAD = {
     "id": "thread_123",
@@ -13,6 +13,20 @@ _THREAD_PAYLOAD = {
     "unexpected_upstream_field": "kept",
 }
 
+_MESSAGE_PAYLOAD = {
+    "id": "msg_123",
+    "object": "thread.message",
+    "created_at": 1700000000,
+    "thread_id": "thread_123",
+    "role": "assistant",
+    "status": "in_progress",
+    "content": [{"type": "text", "text": {"value": "hi", "annotations": []}}],
+    "metadata": {"origin": "unit-test"},
+    "run_id": "run_123",
+    "assistant_id": "asst_123",
+    "unexpected_upstream_field": "kept",
+}
+
 _COMMON_ARGS = {
     "api_key": "test-key",
     "api_base": "https://api.openai.com/v1",
@@ -22,23 +36,26 @@ _COMMON_ARGS = {
 }
 
 
-def _handler(request: httpx.Request) -> httpx.Response:
-    return httpx.Response(200, json=_THREAD_PAYLOAD)
+def _transport(payload: dict) -> httpx.MockTransport:
+    def handler(request: httpx.Request) -> httpx.Response:
+        return httpx.Response(200, json=payload)
+
+    return httpx.MockTransport(handler)
 
 
-def _async_client() -> AsyncOpenAI:
+def _async_client(payload: dict = _THREAD_PAYLOAD) -> AsyncOpenAI:
     """A real AsyncOpenAI wired to a mock transport, so the SDK's own response parsing
     runs and the handler under test receives exactly what production would."""
     return AsyncOpenAI(
         api_key="test-key",
-        http_client=httpx.AsyncClient(transport=httpx.MockTransport(_handler)),
+        http_client=httpx.AsyncClient(transport=_transport(payload)),
     )
 
 
-def _sync_client() -> OpenAI:
+def _sync_client(payload: dict = _THREAD_PAYLOAD) -> OpenAI:
     return OpenAI(
         api_key="test-key",
-        http_client=httpx.Client(transport=httpx.MockTransport(_handler)),
+        http_client=httpx.Client(transport=_transport(payload)),
     )
 
 
@@ -73,6 +90,64 @@ async def test_async_thread_responses_preserve_declared_fields():
     _assert_thread(retrieved)
 
 
+def _assert_message(result: object) -> None:
+    assert isinstance(result, OpenAIMessage)
+    assert result.id == "msg_123"
+    assert result.thread_id == "thread_123"
+    assert result.role == "assistant"
+    assert result.metadata == {"origin": "unit-test"}
+    assert result.model_dump()["unexpected_upstream_field"] == "kept"
+
+
+@pytest.mark.asyncio
+async def test_a_add_message_preserves_fields_and_defaults_status():
+    api = OpenAIAssistantsAPI()
+
+    result = await api.a_add_message(
+        thread_id="thread_123",
+        message_data={"role": "user", "content": "hi"},
+        client=_async_client(_MESSAGE_PAYLOAD),
+        **_COMMON_ARGS,
+    )
+
+    _assert_message(result)
+    assert result.status == "in_progress"
+
+    without_status = {k: v for k, v in _MESSAGE_PAYLOAD.items() if k != "status"}
+    defaulted = await api.a_add_message(
+        thread_id="thread_123",
+        message_data={"role": "user", "content": "hi"},
+        client=_async_client(without_status),
+        **_COMMON_ARGS,
+    )
+
+    assert defaulted.status == "completed"
+
+
+def test_sync_add_message_preserves_fields_and_defaults_status():
+    api = OpenAIAssistantsAPI()
+
+    result = api.add_message(
+        thread_id="thread_123",
+        message_data={"role": "user", "content": "hi"},
+        client=_sync_client(_MESSAGE_PAYLOAD),
+        **_COMMON_ARGS,
+    )
+
+    _assert_message(result)
+    assert result.status == "in_progress"
+
+    without_status = {k: v for k, v in _MESSAGE_PAYLOAD.items() if k != "status"}
+    defaulted = api.add_message(
+        thread_id="thread_123",
+        message_data={"role": "user", "content": "hi"},
+        client=_sync_client(without_status),
+        **_COMMON_ARGS,
+    )
+
+    assert defaulted.status == "completed"
+
+
 def test_sync_thread_responses_preserve_declared_fields():
     api = OpenAIAssistantsAPI()
 
diff --git a/type-discipline-budget.json b/type-discipline-budget.json
index 45b3ec68ca1..573970a5561 100644
--- a/type-discipline-budget.json
+++ b/type-discipline-budget.json
@@ -27,7 +27,7 @@
     "limit": 0
   },
   "LIT010": {
-    "limit": 16707
+    "limit": 16701
   },
   "LIT011": {
     "limit": 5591