Skip to content

fix(core): prevent cross-type content block merging in merge_lists #35984

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Mason Daugherty (mdrxy) wants to merge 2 commits into
base: master
Choose a base branch
from
+31 −0
Open

fix(core): prevent cross-type content block merging in merge_lists #35984

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ad64946
fix(core): prevent cross-type content block merging in merge_lists
mdrxy Mar 17, 2026
d8537d1
Merge branch 'master' into mdrxy/fix-merge-list
mdrxy Mar 17, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 10 additions & 0 deletions libs/core/langchain_core/utils/_merge.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -120,6 +120,16 @@ def merge_lists(left: list | None, *others: list | None) -> list | None:
if (
"index" in e_left
and e_left["index"] == e["index"] # index matches
# Prevent text blocks from merging with non-text
# blocks that happen to share the same index (e.g.,
# streaming text at index 0 vs tool_call_chunk at
# index 0 from the API). This is a text-vs-
# everything-else partition; non-text blocks at the
# same index may still merge with each other.
and (
(e_left.get("type") == "text")
== (e.get("type") == "text")
)
and ( # IDs not inconsistent
e_left.get("id") in (None, "")
or e.get("id") in (None, "")
Expand Down
21 changes: 21 additions & 0 deletions libs/core/tests/unit_tests/utils/test_utils.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,27 @@ def test_generation_chunk_addition_type_error() -> None:
[{"no_index": "b"}],
[{"no_index": "a"}, {"no_index": "b"}],
),
# Text and non-text blocks with same index should NOT merge
(
[{"index": 0, "type": "text", "text": "hello"}],
[{"index": 0, "type": "tool_call_chunk", "name": "foo", "args": "{}"}],
[
{"index": 0, "type": "text", "text": "hello"},
{"index": 0, "type": "tool_call_chunk", "name": "foo", "args": "{}"},
],
),
# Two text blocks with same index should still merge
(
[{"index": 0, "type": "text", "text": "hel"}],
[{"index": 0, "type": "text", "text": "lo"}],
[{"index": 0, "type": "text", "text": "hello"}],
),
# Two non-text blocks with same index should still merge
(
[{"index": 0, "type": "tool_call_chunk", "args": '{"a'}],
[{"index": 0, "type": "tool_call_chunk", "args": '": 1}'}],
[{"index": 0, "type": "tool_call_chunk", "args": '{"a": 1}'}],
),
],
)
def test_merge_lists(
Expand Down
Loading