How do I use LangChain to build conversational agents with context?

To build conversational agents with context using LangChain, you primarily use its memory management components. LangChain provides tools to store and retrieve past interactions, allowing the agent to maintain context across multiple turns in a conversation. This is achieved through memory classes like ConversationBufferMemory or ConversationBufferWindowMemory, which retain previous user inputs, agent responses, or other metadata. For example, ConversationBufferMemory stores the entire conversation history as a list, while ConversationBufferWindowMemory keeps only the last few exchanges to avoid overload. To use this, you initialize the memory object, integrate it into your agent or chain, and ensure it’s updated after each interaction. The memory is then injected into the prompt template, providing the agent with the full conversation history when generating responses.

Implementing this involves three key steps. First, define the memory component, such as memory = ConversationBufferMemory(). Next, create an agent or chain (like ConversationChain) and pass the memory object to it. For instance, agent = initialize_agent(tools, llm, memory=memory). During interactions, the memory is automatically updated when you call agent.run("user input"). The agent’s prompt template combines the current input with stored context to generate context-aware replies. For example, if a user asks, “What’s the weather in Tokyo?” followed by “What about tomorrow?”, the agent uses the stored “Tokyo” context to infer the second query refers to Tokyo’s weather. Without explicit memory handling, each query would be treated in isolation, leading to fragmented conversations.

Best practices include balancing context retention and performance. Storing too much history can lead to long prompts, increased costs, and slower responses. To mitigate this, use ConversationBufferWindowMemory to limit history to the last k interactions or implement summarization. For instance, ConversationSummaryMemory condenses past exchanges into a concise summary. Additionally, sanitize inputs to avoid storing sensitive data and test edge cases like abrupt topic changes. For example, if a user switches from discussing weather to flight bookings, the agent should reset or filter irrelevant context. By tailoring memory strategies to your use case—such as session-based storage for web apps or persistent databases for long-term interactions—you can build robust, context-aware agents efficiently.