fix(core): support for Python 3.14 by cbornet · Pull Request #33461 · langchain-ai/langchain

Christophe Bornet (cbornet) · 2025-10-13T16:14:46Z

Fix detection of support of context in asyncio.create_task
Fix: in Python 3.14 asyncio.get_event_loop() raises an exception if there's no running loop
Bump pydantic to version 2.12
Skips tests with pydantic v1 models as they are not supported with Python 3.14
Run core tests with Python 3.14 in CI.

codspeed-hq · 2025-10-13T16:17:56Z

CodSpeed Performance Report

Merging #33461 will degrade performances by 12.27%

_{Comparing cbornet:python-3.14 (f0e5668) with master (1d22735)}

⚠️

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Summary

❌ 4 (👁 4) regressions
✅ 9 untouched
⏩ 21 skipped¹

Benchmarks breakdown

	Mode	Benchmark	`BASE`	`HEAD`	Change
👁	WallTime	`test_import_time[ChatPromptTemplate]`	572.6 ms	652.6 ms	-12.27%
👁	WallTime	`test_import_time[LangChainTracer]`	412.3 ms	461.9 ms	-10.73%
👁	WallTime	`test_import_time[PydanticOutputParser]`	505.2 ms	574.5 ms	-12.05%
👁	WallTime	`test_import_time[RunnableLambda]`	473 ms	534.9 ms	-11.57%

21 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Christophe Bornet (cbornet) · 2025-10-13T16:18:53Z

        The coroutine with the context.
    """
-    if asyncio_accepts_context():
+    if sys.version_info >= (3, 11):


The signature we get in py314 is asyncio.create_task(coro, **kwargs) so we can't check the presence of context.
There's very little chance that support for context in create_task will ever be removed so I think we can just do a version check here.

Is it possible to fix the implementation of the function: asyncio_accepts_context instead of not using it?

Christophe Bornet (cbornet) · 2025-10-13T16:39:34Z


-        loop = asyncio.get_event_loop()
+        try:
+            loop = asyncio.get_event_loop()


asyncio.get_event_loop raises an exception in Python 3.14 if there's no running loop (was a warning in previous versions)

Eugene Yurtsev (eyurtsev)

Looks very reasonable to me left a few nit comments

Eugene Yurtsev (eyurtsev) · 2025-10-13T18:21:55Z

        The coroutine with the context.
    """
-    if asyncio_accepts_context():
+    if sys.version_info >= (3, 11):


Is it possible to fix the implementation of the function: asyncio_accepts_context instead of not using it?

Eugene Yurtsev (eyurtsev) · 2025-10-13T18:24:46Z

+        f_or_c: Literal["F", "C"]
+        forecast: str
+
+    _FORECAST_MODELS_TYPES |= type[ForecastV1]


_FORECAST_MODELS_TYPES -- which type is this? something looks off. If it's meant to be a set or a list could we use the dedicated APIs for adding an element instead of relying on the operator shorthand (|=) to maximize for readability?

_FORECAST_MODELS_TYPES is a typing.Union of types. Used for type checking. I don’t think there is an API to do this. But there’s maybe a simpler way to write it. I’ll have a look.

I tried to simplify. PTAL.

Eugene Yurtsev (eyurtsev) · 2025-10-13T18:26:46Z



+@pytest.mark.skipif(
+    sys.version_info >= (3, 14), reason="Pydantic v1 not supported with Python 3.14+"


Nit: could be helpful to paraphrase the reason a bit (wording is confusing w/ respect to whether this is pydantic 1 or pydantic 2's v1 namespace)

You could say The pydantic.v1 namespace is not supported with python 3.14+ or something like that (to make it clear that it's specifically v1 within pydantic 2)

Sure. Good idea!

Christophe Bornet (cbornet) · 2025-10-14T16:06:31Z

Eugene Yurtsev (@eyurtsev) in the end, I added the upgrade to pydantic 2.12 to this PR.
This way it can be validated in CI with Python 3.14.

Christophe Bornet (cbornet) requested a review from Eugene Yurtsev (eyurtsev) as a code owner October 13, 2025 16:14

github-actions Bot added core `langchain-core` package issues & PRs fix For PRs that implement a fix labels Oct 13, 2025

Christophe Bornet (cbornet) commented Oct 13, 2025

View reviewed changes

Christophe Bornet (cbornet) force-pushed the python-3.14 branch from 0f73756 to 53a7aed Compare October 13, 2025 16:38

Christophe Bornet (cbornet) commented Oct 13, 2025

View reviewed changes

github-actions Bot added fix For PRs that implement a fix and removed fix For PRs that implement a fix labels Oct 13, 2025

Christophe Bornet (cbornet) force-pushed the python-3.14 branch 3 times, most recently from c05fe27 to 42fcb96 Compare October 13, 2025 17:04

github-actions Bot added fix For PRs that implement a fix and removed fix For PRs that implement a fix labels Oct 13, 2025

Eugene Yurtsev (eyurtsev) reviewed Oct 13, 2025

View reviewed changes

Eugene Yurtsev (eyurtsev) self-assigned this Oct 13, 2025

Christophe Bornet (cbornet) force-pushed the python-3.14 branch from 48a070e to 9447bf6 Compare October 14, 2025 09:01

Christophe Bornet (cbornet) mentioned this pull request Oct 14, 2025

fix: support python 3.14 in various projects #33477

Closed

Christophe Bornet (cbornet) force-pushed the python-3.14 branch 2 times, most recently from b845d61 to 29c5034 Compare October 14, 2025 15:40

Christophe Bornet (cbornet) requested review from Bagatur (baskaryan) and ccurme (ccurme) as code owners October 14, 2025 15:42

github-actions Bot added infra PRs made that include chores, devops, repo meta changes fix For PRs that implement a fix and removed fix For PRs that implement a fix infra PRs made that include chores, devops, repo meta changes labels Oct 14, 2025

Christophe Bornet (cbornet) force-pushed the python-3.14 branch from 7b5399a to 0a8468d Compare October 14, 2025 16:05

github-actions Bot added the infra PRs made that include chores, devops, repo meta changes label Oct 14, 2025

Christophe Bornet (cbornet) mentioned this pull request Oct 14, 2025

fix(core): support pydantic 2.12 #33422

Closed

Christophe Bornet (cbornet) requested a review from Eugene Yurtsev (eyurtsev) October 14, 2025 16:10

Eugene Yurtsev (eyurtsev) approved these changes Oct 14, 2025

View reviewed changes

Christophe Bornet (cbornet) force-pushed the python-3.14 branch from b09f387 to e2a887b Compare October 15, 2025 09:51

Christophe Bornet (cbornet) added 5 commits October 16, 2025 19:12

fix(core): support for Python 3.14

96fcaea

Changes following review

e081349

feat(core): support pydantic 2.12

e6f9f4e

Test core with Python 3.14

9e6ee07

fix lint

60b13f8

Christophe Bornet (cbornet) force-pushed the python-3.14 branch from e2a887b to 60b13f8 Compare October 16, 2025 17:16

Merge branch 'master' into python-3.14

26e3fa2

Mason Daugherty (mdrxy) approved these changes Oct 17, 2025

View reviewed changes

Sydney Runkle (sydney-runkle) approved these changes Oct 17, 2025

View reviewed changes

Merge branch 'master' into python-3.14

f0e5668

Sydney Runkle (sydney-runkle) merged commit 2d5efd7 into langchain-ai:master Oct 17, 2025
72 checks passed

Christophe Bornet (cbornet) deleted the python-3.14 branch October 17, 2025 10:12

Ülgen Sarıkavak (ulgens) mentioned this pull request Feb 3, 2026

Python 3.14 support #34441

Open

28 tasks

Maxime Grenu (cluster2600) mentioned this pull request Mar 12, 2026

Python 3.14 support: langchain Chain.dict() shadows builtin under PEP 649 NVIDIA-NeMo/Guardrails#1720

Open



		@pytest.mark.skipif(
		sys.version_info >= (3, 14), reason="Pydantic v1 not supported with Python 3.14+"

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Merging #33461 will degrade performances by 12.27%

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Christophe Bornet (cbornet) Oct 13, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Christophe Bornet (cbornet) commented Oct 14, 2025

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Christophe Bornet (cbornet) commented Oct 13, 2025 •

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