diff --git a/src/openai/lib/_parsing/_responses.py b/src/openai/lib/_parsing/_responses.py
index 232718cef6..5a1b76c4c6 100644
--- a/src/openai/lib/_parsing/_responses.py
+++ b/src/openai/lib/_parsing/_responses.py
@@ -58,7 +58,10 @@ def parse_response(
 ) -> ParsedResponse[TextFormatT]:
     output_list: List[ParsedResponseOutputItem[TextFormatT]] = []
 
-    for output in response.output:
+    # `response.output` can be None for incomplete/failed/reasoning-only
+    # responses (and via some proxy/aggregator backends); guard so the stream
+    # parser yields an empty output instead of raising TypeError.
+    for output in (response.output or []):
         if output.type == "message":
             content_list: List[ParsedContent[TextFormatT]] = []
             for item in output.content:
diff --git a/tests/lib/responses/test_parse_response_none_output.py b/tests/lib/responses/test_parse_response_none_output.py
new file mode 100644
index 0000000000..def3255847
--- /dev/null
+++ b/tests/lib/responses/test_parse_response_none_output.py
@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from openai._types import omit
+from openai.lib._parsing._responses import parse_response
+from openai.types.responses import Response
+
+
+def _minimal_response(**overrides: object) -> Response:
+    # Build a Response with the required scalar fields set; `output` is the
+    # field under test. Uses construct() to avoid pulling a full live payload.
+    base: dict[str, object] = dict(
+        id="resp_test",
+        created_at=0.0,
+        error=None,
+        incomplete_details=None,
+        instructions=None,
+        metadata=None,
+        model="gpt-4o-mini",
+        object="response",
+        output=[],
+        parallel_tool_calls=True,
+        temperature=1.0,
+        tool_choice="auto",
+        tools=[],
+        top_p=1.0,
+    )
+    base.update(overrides)
+    return Response.construct(**base)
+
+
+def test_parse_response_handles_none_output() -> None:
+    # `output` can be None for incomplete/failed/reasoning-only responses and
+    # via some proxy/aggregator backends. parse_response must not raise
+    # TypeError('NoneType' object is not iterable) — it should yield empty output.
+    response = _minimal_response(output=None)
+
+    parsed = parse_response(text_format=omit, input_tools=None, response=response)
+
+    assert parsed.output == []