# LangChain 1.4.0

- Product: LangChain (https://whatsnew.fyi/product/langchain)
- Vendor: LangChain
- Date: 2026-09-03
- Version: 1.4.0
- Original notes: https://github.com/langchain-ai/langchain/releases/tag/langchain%3D%3D1.4.0
- Permalink: https://whatsnew.fyi/product/langchain/releases/1.4.0

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

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- **added** — Add langchain.mcp namespace and MCPAdapter for Model Context Protocol support
- **added** — Add runnable langchain.mcp examples to documentation
- **changed** — Omit middleware trace inputs in anthropic and langchain for performance improvement
- **fixed** — Include model destination in agent tool routing
- **changed** — Bump vcrpy test dependency minimum to version 8.2.0

Changes since langchain==1.3.18

docs(langchain): runnable `langchain.mcp` examples (#39976)
feat(langchain): `langchain.mcp` namespace, `MCPAdapter` (#39939)
perf(anthropic,langchain): omit middleware trace inputs (#40098)
fix(langchain): include model destination in agent tool routing (#38355)
chore(langchain): bump vcrpy test dependency minimum to `>=8.2.0` (#39942)