Letta, formerly MemGPT, is a platform for building stateful agents whose memory persists and changes across conversations. The current source lives in the letta-ai/letta-code repository, which contains the agent harness, an interactive terminal UI, an App Server, messaging channels, and the runtime behind the desktop and web apps; this repository is the project landing page, and the retired V1 server is kept on an archive branch without support.
You install the CLI from npm, launch the terminal UI with letta, or run letta server to host agents locally or on your own infrastructure. The same agents are reachable through a desktop app for macOS, Windows, and Linux, a browser client at chat.letta.com, and channels for Slack, Telegram, Discord, WhatsApp, Signal, and custom integrations. A TypeScript Agent SDK embeds agents in applications, and Letta Cloud keeps agent memory, identity, and conversations available across machines.
Agent behaviour is shaped through skills, mods, permissions, schedules, secrets, and subagents; memory is organised in a file-system-like MemFS with shared memory between agents and a background consolidation process. Agents can run on your own machine or in cloud sandboxes, and integrations exist for GitHub, Slack, and the Agent Client Protocol (ACP).
Features
- Stateful memory: agents keep long-term memory across conversations, organised through MemFS with shared memory across agents
- CLI and terminal UI: letta launches an interactive session with slash commands and a headless mode
- App Server: letta server runs agents locally or self-hosted, with a documented protocol lifecycle and external tools
- Multiple front ends: desktop app, browser client, and channels for Slack, Telegram, Discord, WhatsApp, Signal, and custom channels
- Agent SDK: a TypeScript SDK for building agents into applications
- Letta Cloud: hosted agents with memory, identity, and conversations synced across computers
- Compute options: bring your own machine or run in cloud sandboxes, with session teleportation between them
- Configuration surface: skills, mods, permissions, schedules, secrets, and subagents
- Integrations: GitHub, Slack, and ACP
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