Letta

Letta is a platform for building stateful AI agents with transparent, persistent memory (rooted in the MemGPT research). It ships a developer-first Agent Development Environment (ADE) for designing, observing, and editing agent state in real time, plus a REST API and Python/TypeScript SDKs to deploy agents as microservices. Agents are model-agnostic, support custom tools, and can connect to external tool libraries through Model Context Protocol (MCP).

You can self-host from the open-source repo or use Letta Cloud to create, version, and operate agents at scale with templates, monitoring, and observability. A cross-platform Letta Desktop app is available for local development. The platform supports BYO LLM API keys, filesystem-backed knowledge, multi-agent patterns with shared memory, and portability via an agent file format.