Skip to main content

Getting Started: Memory

info

Conceptual Guide

Memory is the concept of storing and retrieving data in the process of a conversation. There are two main methods, loadMemoryVariables and saveContext. The first method is used to retrieve data from memory (optionally using the current input values), and the second method is used to store data in memory.

export type InputValues = Record<string, any>;

export type OutputValues = Record<string, any>;

interface BaseMemory {
  loadMemoryVariables(values: InputValues): Promise<MemoryVariables>;

  saveContext(
    inputValues: InputValues,
    outputValues: OutputValues
  ): Promise<void>;
}
note

Do not share the same memory instance between two different chains, a memory instance represents the history of a single conversation

note

If you deploy your LangChain app on a serverless environment do not store memory instances in a variable, as your hosting provider may have reset it by the next time the function is called.

All Memory classes​

Advanced​

To implement your own memory class you have two options:

Subclassing BaseChatMemory​

This is the easiest way to implement your own memory class. You can subclass BaseChatMemory, which takes care of saveContext by saving inputs and outputs as Chat Messages, and implement only the loadMemoryVariables method. This method is responsible for returning the memory variables that are relevant for the current input values.

abstract class BaseChatMemory extends BaseMemory {
  chatHistory: ChatMessageHistory;

  abstract loadMemoryVariables(values: InputValues): Promise<MemoryVariables>;
}

Subclassing BaseMemory​

If you want to implement a more custom memory class, you can subclass BaseMemory and implement both loadMemoryVariables and saveContext methods. The saveContext method is responsible for storing the input and output values in memory. The loadMemoryVariables method is responsible for returning the memory variables that are relevant for the current input values.

abstract class BaseMemory {
  abstract loadMemoryVariables(values: InputValues): Promise<MemoryVariables>;

  abstract saveContext(
    inputValues: InputValues,
    outputValues: OutputValues
  ): Promise<void>;
}