diff --git a/src/openai/types/beta/beta_response_steer_input.py b/src/openai/types/beta/beta_response_steer_input.py
index aac528e60b..e86bf916bb 100644
--- a/src/openai/types/beta/beta_response_steer_input.py
+++ b/src/openai/types/beta/beta_response_steer_input.py
@@ -35,8 +35,8 @@ class ResponseSteerInputItemListMessage(BaseModel):
     role: Literal["user"]
     """The message role. Always `user`."""
 
-    type: Literal["message"]
-    """The item type. Always `message`."""
+    type: Optional[Literal["message"]] = None
+    """The optional item type. When provided, always `message`."""
 
     id: Optional[str] = None
     """The unique ID of this message item."""
@@ -116,9 +116,9 @@ class ResponseSteerInputItemListFunctionCallOutput(BaseModel):
     """
 
 
-ResponseSteerInputItemList: TypeAlias = Annotated[
-    Union[ResponseSteerInputItemListMessage, ResponseSteerInputItemListFunctionCallOutput],
-    PropertyInfo(discriminator="type"),
+ResponseSteerInputItemList: TypeAlias = Union[
+    ResponseSteerInputItemListMessage,
+    ResponseSteerInputItemListFunctionCallOutput,
 ]
 
 BetaResponseSteerInput: TypeAlias = Union[str, List[ResponseSteerInputItemList]]
diff --git a/src/openai/types/responses/response_steer_input.py b/src/openai/types/responses/response_steer_input.py
index 78426ab22c..0cfa6027ef 100644
--- a/src/openai/types/responses/response_steer_input.py
+++ b/src/openai/types/responses/response_steer_input.py
@@ -26,8 +26,8 @@ class ResponseSteerInputItemListMessage(BaseModel):
     role: Literal["user"]
     """The message role. Always `user`."""
 
-    type: Literal["message"]
-    """The item type. Always `message`."""
+    type: Optional[Literal["message"]] = None
+    """The optional item type. When provided, always `message`."""
 
     id: Optional[str] = None
     """The unique ID of this message item."""
@@ -94,9 +94,9 @@ class ResponseSteerInputItemListFunctionCallOutput(BaseModel):
     """
 
 
-ResponseSteerInputItemList: TypeAlias = Annotated[
-    Union[ResponseSteerInputItemListMessage, ResponseSteerInputItemListFunctionCallOutput],
-    PropertyInfo(discriminator="type"),
+ResponseSteerInputItemList: TypeAlias = Union[
+    ResponseSteerInputItemListMessage,
+    ResponseSteerInputItemListFunctionCallOutput,
 ]
 
 ResponseSteerInput: TypeAlias = Union[str, List[ResponseSteerInputItemList]]
diff --git a/tests/test_response_steer_failed_event_types.py b/tests/test_response_steer_failed_event_types.py
new file mode 100644
index 0000000000..adc491bb46
--- /dev/null
+++ b/tests/test_response_steer_failed_event_types.py
@@ -0,0 +1,42 @@
+from openai.types.beta.beta_response_steer_failed_event import BetaResponseSteerFailedEvent
+from openai.types.beta.beta_response_steer_input import (
+    ResponseSteerInputItemListMessage as BetaResponseSteerInputItemListMessage,
+)
+from openai.types.responses.response_steer_failed_event import ResponseSteerFailedEvent
+from openai.types.responses.response_steer_input import ResponseSteerInputItemListMessage
+
+
+def _failed_event_payload() -> dict[str, object]:
+    return {
+        "error": {
+            "code": "invalid_input",
+            "message": "Invalid steering input",
+            "type": "invalid_request_error",
+        },
+        "sequence_number": 1,
+        "steer": {
+            "input": [{"role": "user", "content": "continue"}],
+            "previous_response_id": "resp_test",
+        },
+        "type": "response.steer.failed",
+    }
+
+
+def test_failed_steer_event_parses_message_without_type() -> None:
+    event = ResponseSteerFailedEvent.model_validate(_failed_event_payload())
+
+    assert isinstance(event.steer.input, list)
+    message = event.steer.input[0]
+    assert isinstance(message, ResponseSteerInputItemListMessage)
+    assert message.role == "user"
+    assert message.type is None
+
+
+def test_beta_failed_steer_event_parses_message_without_type() -> None:
+    event = BetaResponseSteerFailedEvent.model_validate(_failed_event_payload())
+
+    assert isinstance(event.steer.input, list)
+    message = event.steer.input[0]
+    assert isinstance(message, BetaResponseSteerInputItemListMessage)
+    assert message.role == "user"
+    assert message.type is None