Letta vs Zep (2026)
Updated March 10, 2026
Overview
Letta (formerly MemGPT) is an open-source framework for building AI agents with long-term memory and self-editing capabilities. It implements a virtual context management system that allows LLMs to manage their own memory hierarchy, enabling persistent state, unbounded context, and adaptive memory across conversations.
Zep is a long-term memory service for AI assistants and agents. It stores conversation history, extracts facts and entities, builds temporal knowledge graphs, and enables semantic search across past interactions. Zep helps AI applications recall relevant context from previous conversations, making chatbots and agents feel more natural and personalized. Available as open-source and cloud-hosted.
Key features
Core capabilities each platform advertises.
- Memory infrastructure for AI assistants
- Dialog classification and extraction
- Integration with LangChain and LlamaIndex
- Structured and unstructured memory storage
- Memory search with temporal awareness
Strengths and tradeoffs
What each tool does well, and the limitations to keep in mind.
Pros
- Advanced structured memory with entities, facts, and timelines
- Extreme interpretability with human-readable memory
- Strong balance between flexibility and production readiness
- USD 10M seed funding validates technology approach
Cons
- Requires architectural decisions around vector stores and RAG
- Not a plug-and-play solution—needs developer expertise
- Community feedback suggests learning curve for optimal use
Pros
- AI memory purpose-built
- 100k free messages
- Self-hosted option
Cons
- Message limits
- Scaling costs
Letta or Zep — which should you choose?
Choose Letta if you wantChoose if you want
Choose Zep if you wantChoose if you want
- Enterprise AI assistants with memory
- Customer service bots that remember past issues
- Personalized recommendation agents
- Multi-turn conversation management
- Context-aware AI applications
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