test(core): remove stale xfail from test_sync_in_sync_lambdas

[pufuki]

Submission checklist

• This is a bug, not a usage question.
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• This is not related to the langchain-community package.
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Package (Required)

• langchain
• langchain-openai
• langchain-anthropic
• langchain-classic
• langchain-core
• langchain-model-profiles
• langchain-tests
• langchain-text-splitters
• langchain-chroma
• langchain-deepseek
• langchain-exa
• langchain-fireworks
• langchain-groq
• langchain-huggingface
• langchain-mistralai
• langchain-nomic
• langchain-ollama
• langchain-openrouter
• langchain-perplexity
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Related Issues / PRs

No response

Reproduction Steps / Example Code (Python)

- Run this command in libs/core directory:

- pytest tests/unit_tests/runnables/test_runnable_events_v1.py::test_sync_in_sync_lambdas -v

- Expected: Test passes (currently shows XPASS - passes but marked xfail)

Error Message and Stack Trace (if applicable)

tests/unit_tests/runnables/test_runnable_events_v1.py::test_sync_in_sync_lambdas XPASS

Description

• The test test_sync_in_sync_lambdas in libs/core/tests/unit_tests/runnables/test_runnable_events_v1.py:2152 is marked with @pytest.mark.xfail but now passes (shows XPASS).
• Current behavior: Test shows XPASS (passes but marked as expected to fail)
• Expected behavior: Test runs as a normal passing test (no xfail marker)
• Reason: The xfail reason was "missing functionality in _transform_stream_with_config" , that functionality has been implemented since the xfail was added.

System Info

System Information

OS: Linux
OS Version: #1 SMP PREEMPT_DYNAMIC Tue, 11 Aug 2026 09:16:08 +0000
Python Version: 3.12.12 (main, Feb 12 2026, 00:42:14) [Clang 21.1.4 ]

Package Information

langchain_core: 1.5.3
langsmith: 0.8.18
langchain_protocol: 0.0.17
langchain_tests: 1.1.9
langchain_text_splitters: 1.1.2

Optional packages not installed

deepagents
deepagents-cli

Other Dependencies

httpx: 0.28.1
jsonpatch: 1.33
numpy: 2.3.5
orjson: 3.11.6
packaging: 26.0
pydantic: 2.12.5
pytest: 9.0.3
pytest-asyncio: 1.3.0
pytest-benchmark: 5.2.3
pytest-codspeed: 4.3.0
pytest-recording: 0.13.4
pytest-socket: 0.7.0
pyyaml: 6.0.3
requests: 2.33.0
requests-toolbelt: 1.0.0
rich: 14.2.0
syrupy: 5.1.0
tenacity: 9.1.4
typing-extensions: 4.15.0
uuid-utils: 0.16.0
vcrpy: 8.2.1
websockets: 16.0
wrapt: 2.0.1
xxhash: 3.6.0
zstandard: 0.25.0

Social handles (optional)

No response

[gitbalaji]

Hi, I'd like to work on this. Could a maintainer please assign it to me?

[poorpaper]

I understand that test_sync_in_sync_lambdas now passes but is still marked xfail, so the suite reports an XPASS for behavior that is already implemented. I propose removing only the stale pytest.mark.xfail annotation, keeping the test body unchanged, and validating the change with the targeted runnable-events test plus the relevant langchain-core formatting and lint checks. Could a maintainer please confirm that this minimal approach is appropriate and assign the issue to me before I open a PR?