Python: Fix FoundryChatClient and FoundryAgent silently dropping default_headers

python/packages/foundry/agent_framework_foundry/_agent.py

@@ -198,7 +198,9 @@ def __init__(
             self._should_close_client = True
 
         # Get OpenAI client from project
-        async_client = self.project_client.get_openai_client()
+        async_client = self.project_client.get_openai_client(
+            default_headers=dict(default_headers) if default_headers else None,
+        )
 
         super().__init__(
             async_client=async_client,

python/packages/foundry/agent_framework_foundry/_chat_client.py

@@ -206,7 +206,9 @@ def __init__(
 
         super().__init__(
             model=resolved_model,
-            async_client=project_client.get_openai_client(),
+            async_client=project_client.get_openai_client(
+                default_headers=dict(default_headers) if default_headers else None,
+            ),
             default_headers=default_headers,
             instruction_role=instruction_role,
             compaction_strategy=compaction_strategy,

python/packages/foundry/tests/foundry/test_foundry_agent.py

@@ -80,6 +80,35 @@ def test_raw_foundry_agent_chat_client_init_uses_explicit_parameters() -> None:
     assert all(parameter.kind != inspect.Parameter.VAR_KEYWORD for parameter in signature.parameters.values())
 
 
+def test_raw_foundry_agent_chat_client_init_forwards_default_headers_to_openai_client() -> None:
+    """default_headers must be forwarded into get_openai_client() so the underlying
+    AsyncOpenAI client sends them on every outbound request."""
+    custom_headers = {"x-custom-header": "test-value"}
+    mock_project = MagicMock()
+    mock_project.get_openai_client.return_value = MagicMock()
+
+    RawFoundryAgentChatClient(
+        project_client=mock_project,
+        agent_name="test-agent",
+        default_headers=custom_headers,
+    )
+
+    mock_project.get_openai_client.assert_called_once_with(default_headers=custom_headers)
+
+
+def test_raw_foundry_agent_chat_client_init_without_default_headers_passes_none_to_openai_client() -> None:
+    """When no default_headers are provided, get_openai_client() receives None."""
+    mock_project = MagicMock()
+    mock_project.get_openai_client.return_value = MagicMock()
+
+    RawFoundryAgentChatClient(
+        project_client=mock_project,
+        agent_name="test-agent",
+    )
+
+    mock_project.get_openai_client.assert_called_once_with(default_headers=None)
+
+
 def test_raw_foundry_agent_chat_client_get_agent_reference_with_version() -> None:
     """Test agent reference includes version when provided."""
 

python/packages/foundry/tests/foundry/test_foundry_chat_client.py

@@ -180,6 +180,37 @@ def test_init_with_default_header() -> None:
         assert client.default_headers[key] == value
 
 
+def test_init_forwards_default_headers_to_openai_client() -> None:
+    """default_headers must be forwarded into get_openai_client() so the underlying
+    AsyncOpenAI client sends them on every outbound request."""
+    custom_headers = {"x-custom-header": "test-value"}
+    mock_openai_client = _make_mock_openai_client()
+    project_client = MagicMock()
+    project_client.get_openai_client.return_value = mock_openai_client
+
+    FoundryChatClient(
+        project_client=project_client,
+        model=_TEST_FOUNDRY_MODEL,
+        default_headers=custom_headers,
+    )
+
+    project_client.get_openai_client.assert_called_once_with(default_headers=custom_headers)
+
+
+def test_init_without_default_headers_passes_none_to_openai_client() -> None:
+    """When no default_headers are provided, get_openai_client() receives None."""
+    mock_openai_client = _make_mock_openai_client()
+    project_client = MagicMock()
+    project_client.get_openai_client.return_value = mock_openai_client
+
+    FoundryChatClient(
+        project_client=project_client,
+        model=_TEST_FOUNDRY_MODEL,
+    )
+
+    project_client.get_openai_client.assert_called_once_with(default_headers=None)
+
+
 def test_init_with_project_endpoint_creates_project_client() -> None:
     credential = MagicMock()
     mock_openai_client = _make_mock_openai_client()

python/packages/openai/agent_framework_openai/_shared.py

@@ -199,6 +199,8 @@ def load_openai_service_settings(
         if resolved_model := _resolve_named_setting(openai_settings, openai_model_fields):
             openai_settings["model"] = resolved_model
         if client:
+            if merged_headers:
+                client = client.with_options(default_headers=merged_headers)
             return openai_settings, client, False  # type: ignore[return-value]
         if openai_settings.get("api_key") is not None or api_key_callable is not None:
             resolved_model = _resolve_named_setting(openai_settings, openai_model_fields)
@@ -260,6 +262,8 @@ def load_openai_service_settings(
             f"or the {deployment_env_guidance} environment variable."
         )
     if client:
+        if merged_headers:
+            client = client.with_options(default_headers=merged_headers)
         return azure_settings, client, True  # type: ignore[return-value]
     client_args["default_headers"] = merged_headers
     if endpoint := azure_settings.get("endpoint"):

python/packages/openai/tests/openai/test_openai_shared.py

@@ -12,6 +12,7 @@
     AZURE_OPENAI_TOKEN_SCOPE,
     _ensure_async_token_provider,
     _resolve_azure_credential_to_token_provider,
+    load_openai_service_settings,
 )
 
 
@@ -76,3 +77,61 @@ async def async_provider() -> str:
     result = await wrapper()
 
     assert result == "async-token"
+
+
+def test_load_openai_service_settings_applies_default_headers_to_prebuilt_client() -> None:
+    """When a pre-built client is provided, default_headers must be applied to it.
+
+    load_openai_service_settings used to early-return the pre-built client
+    without applying merged_headers, silently dropping any custom headers the
+    caller passed.
+    """
+    pre_built = MagicMock()
+    new_client = MagicMock()
+    pre_built.with_options.return_value = new_client
+
+    _, client, _ = load_openai_service_settings(
+        model="gpt-4o",
+        api_key=None,
+        credential=None,
+        org_id=None,
+        base_url=None,
+        endpoint=None,
+        api_version=None,
+        default_azure_api_version="2024-05-01-preview",
+        default_headers={"x-custom-header": "test-value"},
+        client=pre_built,
+        env_file_path=None,
+        env_file_encoding=None,
+    )
+
+    pre_built.with_options.assert_called_once()
+    call_kwargs = pre_built.with_options.call_args.kwargs
+    assert call_kwargs.get("default_headers", {}).get("x-custom-header") == "test-value"
+    assert client is new_client
+
+
+def test_load_openai_service_settings_no_headers_still_applies_app_info() -> None:
+    """Even with no default_headers, APP_INFO telemetry headers are applied via with_options."""
+    pre_built = MagicMock()
+    new_client = MagicMock()
+    pre_built.with_options.return_value = new_client
+
+    with patch("agent_framework_openai._shared.APP_INFO", {"User-Agent": "test-agent"}):
+        _, client, _ = load_openai_service_settings(
+            model="gpt-4o",
+            api_key=None,
+            credential=None,
+            org_id=None,
+            base_url=None,
+            endpoint=None,
+            api_version=None,
+            default_azure_api_version="2024-05-01-preview",
+            default_headers=None,
+            client=pre_built,
+            env_file_path=None,
+            env_file_encoding=None,
+        )
+
+    pre_built.with_options.assert_called_once()
+    assert client is new_client