RunnableLambda

RunnableLambda is a core component in LangChain Expression Language (LCEL) used to wrap arbitrary Python functions or callable objects into objects that conform to the Runnable interface protocol. Wrapped functions can be composed in chains with other LCEL components—such as chains, prompts, and models—via pipe operators, supporting both synchronous and asynchronous invocation modes and automatically integrating streaming output, batch processing, and callback tracing. It is the primary means of incorporating custom processing logic into LangChain workflows.