From 11bae75ab5f44ea3c0e23a278ceeab3af843ff1b Mon Sep 17 00:00:00 2001
From: Copilot <copilot@github.com>
Date: Tue, 7 Apr 2026 12:49:36 +0000
Subject: [PATCH 1/2] Guard against empty text in
 _parse_structured_response_value (#5145)

When using response_format with background=True (Responses API), polling
an in-progress response produces empty text. _parse_structured_response_value
unconditionally passed this to model_validate_json/json.loads, causing
ValidationError or JSONDecodeError.

Add an early return of None when text is empty, matching the existing
guard for response_format=None. This allows .value to safely return None
for in-progress background responses.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../packages/core/agent_framework/_types.py   |  2 ++
 python/packages/core/tests/core/test_types.py | 29 +++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/python/packages/core/agent_framework/_types.py b/python/packages/core/agent_framework/_types.py
index 736474de60..87799d0848 100644
--- a/python/packages/core/agent_framework/_types.py
+++ b/python/packages/core/agent_framework/_types.py
@@ -1957,6 +1957,8 @@ class ContinuationToken(TypedDict):
 def _parse_structured_response_value(text: str, response_format: Any | None) -> Any | None:
     if response_format is None:
         return None
+    if not text:
+        return None
     if isinstance(response_format, type) and issubclass(response_format, BaseModel):
         return response_format.model_validate_json(text)
     if isinstance(response_format, Mapping):
diff --git a/python/packages/core/tests/core/test_types.py b/python/packages/core/tests/core/test_types.py
index 23c7dd8cd6..e8dc22acaa 100644
--- a/python/packages/core/tests/core/test_types.py
+++ b/python/packages/core/tests/core/test_types.py
@@ -39,6 +39,7 @@
     _get_data_bytes,
     _get_data_bytes_as_str,
     _parse_content_list,
+    _parse_structured_response_value,
     _validate_uri,
     add_usage_details,
     validate_tool_mode,
@@ -813,6 +814,34 @@ def test_chat_response_with_mapping_response_format() -> None:
     assert response.value["response"] == "Hello"
 
 
+
+def test_parse_structured_response_value_empty_text_with_pydantic_model() -> None:
+    """Empty text should return None instead of raising when response_format is a Pydantic model."""
+    result = _parse_structured_response_value("", OutputModel)
+    assert result is None
+
+
+def test_parse_structured_response_value_empty_text_with_mapping() -> None:
+    """Empty text should return None instead of raising when response_format is a mapping."""
+    result = _parse_structured_response_value("", {"type": "object"})
+    assert result is None
+
+
+def test_chat_response_value_with_empty_text_and_response_format() -> None:
+    """ChatResponse.value should return None when text is empty and response_format is set."""
+    message = Message(role="assistant", contents=[""])
+    response = ChatResponse(messages=message, response_format=OutputModel)
+    assert response.value is None
+
+
+def test_agent_response_value_with_empty_text_and_response_format() -> None:
+    """AgentResponse.value should return None when text is empty and response_format is set."""
+    message = Message(role="assistant", contents=[""])
+    response = AgentResponse(messages=message, response_format=OutputModel)
+    assert response.value is None
+
+
+
 def test_chat_response_value_raises_on_invalid_schema():
     """Test that value property raises ValidationError with field constraint details."""
 

From 85a7dc34b6e48eb1bffc60ebc23d0baaac68f9b6 Mon Sep 17 00:00:00 2001
From: Copilot <copilot@github.com>
Date: Tue, 7 Apr 2026 12:52:29 +0000
Subject: [PATCH 2/2] Python: Fix `response_format` crash on background polling
 with empty text

Fixes #5145
---
 python/packages/core/tests/core/test_types.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/python/packages/core/tests/core/test_types.py b/python/packages/core/tests/core/test_types.py
index e8dc22acaa..cf945dae0e 100644
--- a/python/packages/core/tests/core/test_types.py
+++ b/python/packages/core/tests/core/test_types.py
@@ -814,7 +814,6 @@ def test_chat_response_with_mapping_response_format() -> None:
     assert response.value["response"] == "Hello"
 
 
-
 def test_parse_structured_response_value_empty_text_with_pydantic_model() -> None:
     """Empty text should return None instead of raising when response_format is a Pydantic model."""
     result = _parse_structured_response_value("", OutputModel)
@@ -841,7 +840,6 @@ def test_agent_response_value_with_empty_text_and_response_format() -> None:
     assert response.value is None
 
 
-
 def test_chat_response_value_raises_on_invalid_schema():
     """Test that value property raises ValidationError with field constraint details."""