diff --git a/python/packages/core/agent_framework/_types.py b/python/packages/core/agent_framework/_types.py
index 52df892130e..a91f3203848 100644
--- a/python/packages/core/agent_framework/_types.py
+++ b/python/packages/core/agent_framework/_types.py
@@ -1546,7 +1546,7 @@ def _add_function_call_content(self, other: Content) -> Content:
         return Content(
             "function_call",
             call_id=self_call_id,
-            name=getattr(self, "name", getattr(other, "name", None)),
+            name=getattr(self, "name", None) or getattr(other, "name", None),
             arguments=arguments,
             exception=getattr(self, "exception", None) or getattr(other, "exception", None),
             informational_only=getattr(self, "informational_only", False)
diff --git a/python/packages/core/tests/core/test_types.py b/python/packages/core/tests/core/test_types.py
index 40c7081e092..bb67f936fed 100644
--- a/python/packages/core/tests/core/test_types.py
+++ b/python/packages/core/tests/core/test_types.py
@@ -570,6 +570,21 @@ def test_function_call_content_add_merging_and_errors():
     with raises(ContentError):
         _ = a + b
 
+    # name merging: when the first chunk has no name (e.g. a streaming delta where
+    # the function name arrives later), the merged content must keep the name from
+    # whichever side provides it, regardless of order.
+    # A nameless delta is constructed via Content(...) directly (the factory
+    # from_function_call requires name: str); this mirrors how a streaming
+    # function-call delta with no name yet is represented.
+    a = Content("function_call", call_id="1", name=None, arguments='{"a":')
+    b = Content.from_function_call(call_id="1", name="get_weather", arguments="1}")
+    assert (a + b).name == "get_weather"
+    assert (b + a).name == "get_weather"
+    # both sides missing a name stays None
+    a = Content("function_call", call_id="1", name=None, arguments="")
+    b = Content("function_call", call_id="1", name=None, arguments="")
+    assert (a + b).name is None
+
 
 # region FunctionResultContent