From 617a3d88992b6fa2f8b92a5f024e811bdfc8b212 Mon Sep 17 00:00:00 2001
From: Lichao Chen <3780722+chenlichao@users.noreply.github.com>
Date: Fri, 11 Sep 2026 10:04:22 -0700
Subject: [PATCH] fix(lib): treat null message content as empty in
 parse_response

Responses parsing raised `TypeError: 'NoneType' object is not iterable`
when a message output item had `content: null` - the same class of bug
as null `output` fixed in #3345. Null reaches the parser because stream
events are built without validation, and the same payload also passes
the non-streaming path.

Treat null content as empty with the same `or []` idiom used for null
output, and add a regression test alongside the null-output tests.

Fixes #3840
---
 src/openai/lib/_parsing/_responses.py   |  2 +-
 tests/lib/responses/test_null_output.py | 31 ++++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/openai/lib/_parsing/_responses.py b/src/openai/lib/_parsing/_responses.py
index 81e6b2b983..033e06e6ed 100644
--- a/src/openai/lib/_parsing/_responses.py
+++ b/src/openai/lib/_parsing/_responses.py
@@ -61,7 +61,7 @@ def parse_response(
     for output in response.output or []:
         if output.type == "message":
             content_list: List[ParsedContent[TextFormatT]] = []
-            for item in output.content:
+            for item in output.content or []:
                 if item.type != "output_text":
                     content_list.append(item)
                     continue
diff --git a/tests/lib/responses/test_null_output.py b/tests/lib/responses/test_null_output.py
index 4c782de03a..1394cc0980 100644
--- a/tests/lib/responses/test_null_output.py
+++ b/tests/lib/responses/test_null_output.py
@@ -7,7 +7,10 @@
 from pydantic import BaseModel
 
 from openai import OpenAI, AsyncOpenAI
-from openai.types.responses import ToolParam
+from openai._types import omit
+from openai._models import construct_type_unchecked
+from openai.types.responses import Response, ToolParam
+from openai.lib._parsing._responses import parse_response
 
 
 class Answer(BaseModel):
@@ -123,3 +126,29 @@ async def test_stream_recovers_finalized_output(sync: bool, terminal_output: str
         assert tool.type == "function_call" and tool.status == "completed"
         assert tool.id == "fc_test"
         assert tool.parsed_arguments == {"answer": 4}
+
+
+def test_parse_response_with_null_message_content() -> None:
+    response = construct_type_unchecked(
+        type_=Response,
+        value={
+            "id": "resp_test",
+            "status": "completed",
+            "output": [
+                {
+                    "id": "msg_test",
+                    "type": "message",
+                    "role": "assistant",
+                    "status": "completed",
+                    "content": None,
+                }
+            ],
+        },
+    )
+
+    parsed = parse_response(text_format=omit, input_tools=omit, response=response)
+
+    assert len(parsed.output) == 1
+    message = parsed.output[0]
+    assert message.type == "message"
+    assert message.content == []