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fix(streaming): handle duplicate-index list entries in accumulate_delta #3227

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fix(streaming): handle duplicate-index list entries in accumulate_delta #3227

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be37dee
fix(streaming): handle duplicate-index list entries in accumulate_delta
rmotgi1227 May 11, 2026
6cfb5f6
fix: guard extend() path against empty acc_value list
rmotgi1227 May 11, 2026
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19 changes: 15 additions & 4 deletions src/openai/lib/streaming/_deltas.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,24 @@
def accumulate_delta(acc: dict[object, object], delta: dict[object, object]) -> dict[object, object]:
for key, delta_value in delta.items():
if key not in acc:
acc[key] = delta_value
continue
if is_list(delta_value):
# Initialize an empty list so that list-merge logic below
# handles duplicate-index entries even on the very first chunk.
acc[key] = []
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@chatgpt-codex-connector chatgpt-codex-connector Bot May 11, 2026

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P1 Badge Fix first list chunk duplicate-index merging

When delta_value is a list for a key that is not yet in acc, this initializes acc_value to an empty list, but the existing list branch treats all(isinstance(... ) for x in acc_value) as true for an empty list and just extends the raw delta. As a result, the exact duplicate-index case this commit is meant to fix still leaves two entries at index 0 for inputs like {'tool_calls': [{'index': 0, ...}, {'index': 0, ...}]} instead of merging them, so later chunks continue from a malformed snapshot.

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else:
acc[key] = delta_value
continue

acc_value = acc[key]
if acc_value is None:
acc[key] = delta_value
continue
if is_list(delta_value):
# Same as above: route list deltas through the merge path
# instead of copying the raw array wholesale.
acc[key] = []
acc_value = acc[key]
else:
acc[key] = delta_value
continue

# the `index` property is used in arrays of objects so it should
# not be accumulated like other values e.g.
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