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fix(openai): keep streamed tool calls without an index apart #2028

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fix(openai): keep streamed tool calls without an index apart
pcbeingused333 Oct 20, 2026
7551195
test(openai): cover a tool call without index or id that starts a new…
pcbeingused333 Oct 20, 2026
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27 changes: 21 additions & 6 deletions langfuse/openai.py
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Original file line number Diff line number Diff line change
Expand Up @@ -842,19 +842,34 @@ def _extract_streamed_openai_response(resource: Any, chunks: Any) -> Any:

for raw_tool_call in delta.get("tool_calls", []):
index = _get_attr_or_item(raw_tool_call, "index", None)
tool_call_id = _get_attr_or_item(raw_tool_call, "id", None)
tool_call_type = _get_attr_or_item(raw_tool_call, "type", None)
tool_call_chunk = _get_attr_or_item(
raw_tool_call, "function", None
)

if not isinstance(index, int):
index = len(curr) - 1 if curr else 0
# Some OpenAI-compatible APIs (e.g. Gemini) omit the index
# and send each parallel call whole in its own chunk: a new
# id, or a name without an id, starts a call; anything else
# continues the latest one.
starts_call = not curr or (
(
tool_call_id is not None
and tool_call_id != curr[-1].get("id")
)
or (
tool_call_id is None
and _get_attr_or_item(tool_call_chunk, "name", None)
is not None
)
)
index = len(curr) if starts_call else len(curr) - 1

while len(curr) <= index:
curr.append({"function": {"name": "", "arguments": ""}})

current_tool_call = curr[index]
tool_call_id = _get_attr_or_item(raw_tool_call, "id", None)
tool_call_type = _get_attr_or_item(raw_tool_call, "type", None)
tool_call_chunk = _get_attr_or_item(
raw_tool_call, "function", None
)

if tool_call_id is not None:
current_tool_call["id"] = tool_call_id
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97 changes: 97 additions & 0 deletions tests/unit/test_openai.py
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Original file line number Diff line number Diff line change
Expand Up @@ -401,6 +401,103 @@ def test_streaming_chat_completion_preserves_tool_calls_after_content():
assert metadata == {"finish_reason": "tool_calls"}


def _tool_call_chunk(*, id=None, name=None, arguments=None, finish_reason=None):
# Gemini's OpenAI-compatible API leaves tool_calls[].index unset
return SimpleNamespace(
model="gemini-3.5-flash",
choices=[
SimpleNamespace(
delta=SimpleNamespace(
role=None,
content=None,
function_call=None,
tool_calls=[
SimpleNamespace(
index=None,
id=id,
type="function" if id else None,
function=SimpleNamespace(name=name, arguments=arguments),
)
],
),
finish_reason=finish_reason,
)
],
usage=None,
)


def test_streaming_chat_completion_keeps_parallel_tool_calls_without_index_apart():
_model, completion, _usage, _metadata, _service_tier = (
lf_openai_module._extract_streamed_openai_response(
SimpleNamespace(type="chat"),
[
_tool_call_chunk(
id="call_paris",
name="get_weather",
arguments='{"city": "Paris"}',
),
_tool_call_chunk(
id="call_tokyo",
name="get_weather",
arguments='{"city": "Tokyo"}',
finish_reason="stop",
),
Comment on lines +430 to +445

@greptile-apps greptile-apps Bot Oct 20, 2026

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P2 Name-only calls lack test coverage

Neither new test exercises the rule that a name without an ID starts another call. Both parallel calls have IDs, and the fragment without an ID also has no name. Removing this new branch would therefore leave the tests passing.

Add a test with two calls that omit both index and id, share a function name, and have different arguments. Assert that their arguments stay separate.

Prompt To Fix With AI 
This is a comment left during a code review.
Path: tests/unit/test_openai.py
Line: 430-445

Comment:
**Name-only calls lack test coverage**

Neither new test exercises the rule that a name without an ID starts another call. Both parallel calls have IDs, and the fragment without an ID also has no name. Removing this new branch would therefore leave the tests passing.

Add a test with two calls that omit both `index` and `id`, share a function name, and have different arguments. Assert that their arguments stay separate.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

],
)
)

assert [
(call["id"], call["function"]["arguments"]) for call in completion["tool_calls"]
] == [
("call_paris", '{"city": "Paris"}'),
("call_tokyo", '{"city": "Tokyo"}'),
]


def test_streaming_chat_completion_keeps_tool_calls_without_index_or_id_apart():
_model, completion, _usage, _metadata, _service_tier = (
lf_openai_module._extract_streamed_openai_response(
SimpleNamespace(type="chat"),
[
_tool_call_chunk(name="get_weather", arguments='{"city": "Paris"}'),
_tool_call_chunk(name="get_weather", arguments='{"city": "Tokyo"}'),
],
)
)

assert [
(call["function"]["name"], call["function"]["arguments"])
for call in completion["tool_calls"]
] == [
("get_weather", '{"city": "Paris"}'),
("get_weather", '{"city": "Tokyo"}'),
]


def test_streaming_chat_completion_merges_fragments_of_one_tool_call_without_index():
_model, completion, _usage, _metadata, _service_tier = (
lf_openai_module._extract_streamed_openai_response(
SimpleNamespace(type="chat"),
[
_tool_call_chunk(
id="call_paris", name="get_weather", arguments='{"city"'
),
_tool_call_chunk(arguments=': "Paris"}'),
_tool_call_chunk(id="call_paris", arguments=""),
],
)
)

assert completion["tool_calls"] == [
{
"id": "call_paris",
"type": "function",
"function": {"name": "get_weather", "arguments": '{"city": "Paris"}'},
}
]


def test_response_api_output_serializes_openai_parsed_response_objects():
class ParsedOutput(BaseModel):
name: str
Expand Down