LangChain Python setup: what to pip install and what lives in provider packages

LangChain Python setup

pip install -U langchain gives you the core: agents, messages, tools, chat models, embeddings. It needs Python 3.10 or newer.

Provider packages are separate

Model providers live in their own packages. Install the ones you use:

pip install -U langchain-openai
pip install -U langchain-anthropic

Or pull a provider in as an extra of the core package:

pip install -U "langchain[openai]"
pip install -U "langchain[anthropic]"

Rules

• Do not expect pip install langchain to include OpenAI or Anthropic support. If the import of langchain_openai fails, the fix is installing the provider package, not reinstalling langchain.
• Keep the key in the environment (OPENAIAPIKEY, ANTHROPICAPIKEY). The model classes read it from there by default; do not hardcode it in the script.
• Use uv add langchain / uv add langchain-openai if the project is uv-managed. Mixing pip and uv in one project is how you get two copies of langchain-core fighting each other.

Verified against the official LangChain docs on 2026-09-26. Install: https://docs.langchain.com/oss/python/langchain/install ; model setup: https://docs.langchain.com/oss/python/langchain/models