diff --git a/libs/partners/openai/langchain_openai/chat_models/base.py b/libs/partners/openai/langchain_openai/chat_models/base.py
index aecacb2d25..6560e331eb 100644
--- a/libs/partners/openai/langchain_openai/chat_models/base.py
+++ b/libs/partners/openai/langchain_openai/chat_models/base.py
@@ -5194,6 +5194,20 @@ def _convert_responses_chunk_to_generation_chunk(
         if getattr(chunk.item, "namespace", None) is not None:
             function_call_content["namespace"] = chunk.item.namespace
         content.append(function_call_content)
+    elif (
+        chunk.type == "response.output_item.done" and chunk.item.type == "function_call"
+    ):
+        # The "added" event above records the transient status (typically
+        # "in_progress"); update it here with the terminal status (e.g.
+        # "completed") so a replayed history doesn't send a stale value.
+        _advance(chunk.output_index)
+        content.append(
+            {
+                "type": "function_call",
+                "status": getattr(chunk.item, "status", None),
+                "index": current_index,
+            }
+        )
     elif chunk.type == "response.output_item.done" and chunk.item.type in (
         "compaction",
         "web_search_call",
diff --git a/libs/partners/openai/tests/unit_tests/chat_models/test_base.py b/libs/partners/openai/tests/unit_tests/chat_models/test_base.py
index 1ef3e10837..769c23f52d 100644
--- a/libs/partners/openai/tests/unit_tests/chat_models/test_base.py
+++ b/libs/partners/openai/tests/unit_tests/chat_models/test_base.py
@@ -2662,6 +2662,66 @@ def test__convert_responses_chunk_to_generation_chunk_function_call_status() ->
     assert function_call_block["status"] == "in_progress"
 
 
+def test__convert_responses_chunk_to_generation_chunk_function_call_done_status() -> (
+    None
+):
+    """A streamed function_call's terminal status overwrites the transient one.
+
+    The "added" event reports a transient status (typically "in_progress"),
+    and the "done" event reports the terminal status (e.g. "completed").
+    Merging the two chunks must not concatenate "status" as if it were
+    accumulated text.
+    """
+    added_chunk = MagicMock()
+    added_chunk.type = "response.output_item.added"
+    added_chunk.output_index = 0
+    added_chunk.item = ResponseFunctionToolCall(
+        type="function_call",
+        id="func_123",
+        call_id="call_123",
+        name="get_weather",
+        arguments="",
+        status="in_progress",
+    )
+
+    idx, output_idx, sub_idx, added_generation_chunk = (
+        _convert_responses_chunk_to_generation_chunk(
+            added_chunk,
+            current_index=-1,
+            current_output_index=-1,
+            current_sub_index=-1,
+        )
+    )
+    assert added_generation_chunk is not None
+
+    done_chunk = MagicMock()
+    done_chunk.type = "response.output_item.done"
+    done_chunk.output_index = 0
+    done_chunk.item = ResponseFunctionToolCall(
+        type="function_call",
+        id="func_123",
+        call_id="call_123",
+        name="get_weather",
+        arguments="{}",
+        status="completed",
+    )
+
+    _, _, _, done_generation_chunk = _convert_responses_chunk_to_generation_chunk(
+        done_chunk,
+        current_index=idx,
+        current_output_index=output_idx,
+        current_sub_index=sub_idx,
+    )
+    assert done_generation_chunk is not None
+
+    merged = added_generation_chunk + done_generation_chunk
+    content = merged.message.content
+    assert isinstance(content, list)
+    function_call_block = content[0]
+    assert isinstance(function_call_block, dict)
+    assert function_call_block["status"] == "completed"
+
+
 def test__construct_lc_result_from_responses_api_web_search_response() -> None:
     """Test a response with web search output."""
     from openai.types.responses.response_function_web_search import (