langchain/docs/docs/guides/development/extending_langchain.mdx

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# Extending LangChain

Extending LangChain's base abstractions, whether you're planning to contribute back to the open-source repo or build a bespoke internal integration, is encouraged.

Check out these guides for building your own custom classes for the following modules:

- [Chat models](/docs/modules/model_io/chat/custom_chat_model) for interfacing with chat-tuned language models.
- [LLMs](/docs/modules/model_io/llms/custom_llm) for interfacing with text language models.
- [Output parsers](/docs/modules/model_io/output_parsers/custom) for handling language model outputs.