Letta

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Build agents that actually remember — facts, preferences, and past interactions persist across every session without manual context management.

Agents

★ 4.4(1,300 reviews)freemium

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Overview

Letta (formerly MemGPT) is an agent framework built around stateful long-term memory — agents remember facts across sessions, update their knowledge as conversations evolve, and recall relevant context from arbitrarily long interaction histories. Each agent manages its own memory tiers (working, recall, and archival) and decides what to retain or summarize, solving the context-window problem at the framework level rather than prompting around it.

Key Features

Three-tier memory architecture: working, recall, and archival
Self-directed memory management — agents decide what to store
Cross-session persistence with no manual prompt engineering
REST API and Python SDK for embedding agents in applications
Agent builder UI for configuring memory and persona
Open-source core with managed Letta Cloud option

Pros

• Solves long-term memory without external memory databases or prompting tricks
• Open-source core means full control over data and deployment
• Framework-level memory is more reliable than ad-hoc RAG approaches

Cons

• Memory management adds latency compared to stateless agents
• Cloud pricing is per-step — complex agents with many memory reads get expensive
• Steeper learning curve than simpler stateless frameworks