diff --git a/python/packages/hosting-responses/agent_framework_hosting_responses/_parsing.py b/python/packages/hosting-responses/agent_framework_hosting_responses/_parsing.py
index 62e4bd2b095..313c699d47e 100644
--- a/python/packages/hosting-responses/agent_framework_hosting_responses/_parsing.py
+++ b/python/packages/hosting-responses/agent_framework_hosting_responses/_parsing.py
@@ -147,7 +147,9 @@ def flush() -> None:
         if not isinstance(item, Mapping):
             raise ValueError("each `input` item must be an object")
         item_map = cast("Mapping[str, Any]", item)
-        if item_map.get("type") == "message":
+        # `type` is optional on message items (EasyInputMessage), e.g. {"role": "user", "content": "hi"}.
+        item_type = item_map.get("type")
+        if item_type == "message" or (item_type is None and "role" in item_map):
             flush()
             role = item_map.get("role")
             if not isinstance(role, str) or role not in _RESPONSES_INPUT_MESSAGE_ROLES:
diff --git a/python/packages/hosting-responses/tests/hosting_responses/test_parsing.py b/python/packages/hosting-responses/tests/hosting_responses/test_parsing.py
index b98ccec596a..7d39fc104b3 100644
--- a/python/packages/hosting-responses/tests/hosting_responses/test_parsing.py
+++ b/python/packages/hosting-responses/tests/hosting_responses/test_parsing.py
@@ -82,6 +82,14 @@ def test_message_envelope_with_string_content(self) -> None:
         assert [m.role for m in msgs] == ["system", "user"]
         assert msgs[0].text == "be brief"
 
+    def test_message_envelope_without_type(self) -> None:
+        msgs = messages_from_responses_input([
+            {"role": "developer", "content": "be brief"},
+            {"role": "user", "content": [{"type": "input_text", "text": "hi"}]},
+        ])
+        assert [m.role for m in msgs] == ["developer", "user"]
+        assert [m.text for m in msgs] == ["be brief", "hi"]
+
     def test_message_envelope_with_content_parts(self) -> None:
         msgs = messages_from_responses_input([
             {