release(langchain): 1.4.3 (#40888)

Prepare the `langchain` 1.4.3 patch release. Bumps package metadata and
the lockfile from 1.4.2; no dependency changes or publishing are
performed by this PR.

### PRs included since 1.4.2

- [#40886](https://github.com/langchain-ai/langchain/pull/40886):
Sanitize cache settings for fallback models.
- [#40837](https://github.com/langchain-ai/langchain/pull/40837):
Support Bedrock Mantle chat models in `init_chat_model`.
- [#40844](https://github.com/langchain-ai/langchain/pull/40844):
Recognize GPT-6 structured output without profiles.
- [#40530](https://github.com/langchain-ai/langchain/pull/40530): Repair
invalid tool calls in `create_agent`.
- [#40713](https://github.com/langchain-ai/langchain/pull/40713): Remove
the commented-out Cohere extra.
- [#40626](https://github.com/langchain-ai/langchain/pull/40626): Bump
locked AnyIO from 4.11.0 to 4.14.2.
- [#40794](https://github.com/langchain-ai/langchain/pull/40794):
Correct repository setup guidance and package documentation.

Made by [Open SWE](https://github.com/langchain-ai/open-swe) · [view
thread](https://openswe.langchain.dev/agents/c2dee156-b2b1-573e-8f59-e498d251ae49)
· openai:gpt-6-astra (medium)

Co-authored-by: Mason Daugherty <mdrxy@users.noreply.github.com>
Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>

libs/langchain_v1/langchain/__init__.py

@@ -1,3 +1,3 @@
 """Main entrypoint into LangChain."""
 
-__version__ = "1.4.2"
+__version__ = "1.4.3"

libs/langchain_v1/pyproject.toml

@@ -21,7 +21,7 @@ classifiers = [
     "Topic :: Software Development :: Libraries :: Python Modules",
 ]
 
-version = "1.4.2"
+version = "1.4.3"
 requires-python = ">=3.10.0,<4.0.0"
 dependencies = [
     "langchain-core>=1.6.3,<2.0.0",

libs/langchain_v1/uv.lock

@@ -2282,7 +2282,7 @@ wheels = [
 
 [[package]]
 name = "langchain"
-version = "1.4.2"
+version = "1.4.3"
 source = { editable = "." }
 dependencies = [
     { name = "langchain-core" },