Letta API Platform

The Letta API Platform allows developers to build stateful agents that remember, learn, and improve over time. Letta agents can form living memories about themselves, the world they live in, and your users.

Get started

The Letta API Platform is for developers building agentic applications. If you’re looking for an agent for personal use (like Claude Code or Codex), use Letta Code, available as a desktop app and via the CLI.

There are two ways to build on the Letta API: using the Letta Code SDK, or using the Letta API directly via REST or the client SDKs.

The Letta Code SDK builds on top of the Letta Code harness (which uses the Letta API under the hood) which gives your agent the ability to use call computer-use tools and leverage skills. Agents running in the Letta Code SDK also have access to MemFS, our latest memory system which is git-tracked.

Letta Code SDK Build TypeScript apps on top of Letta Code agents.

Letta API client SDKs TypeScript and Python clients for the Letta API.

Frequently asked questions

For more questions, visit the Letta Discord server.

How can I build a custom agent?

The fastest way to build a custom personal agent is to download Letta Code. You can customize your agent’s behavior by modifying its memory, and extend its abilities by adding skills.

Can I use Letta Code through a UI (not the terminal)?

Yes - Letta Code has a desktop app. View the quickstart to learn more.

The Letta Code SDK allows you to build your own UIs on top of Letta Code agents. See the Letta OSS UI repo for an Electron app example.

Which Letta SDK/API should I use?

We recommend most developers build on the Letta Code SDK, which includes rich support for agent skills and local tool execution / computer use (Bash, Grep, etc). If you are building an agent that does not require skills or local tool execution (e.g. a chatbot), or you require a Python SDK, consider building directly on the Letta API instead.

What’s the difference between Letta Code SDK and the Letta API?

The Letta Code SDK is built on top of the core Letta API, and adds pre-built support for skills and local / client-side tool exeuction.

Product	Use via	Function	Most similar to
Letta Code	Desktop app, Web, Terminal / CLI, Telegram / Slack, GitHub Action	Local tool execution and pre-built computer use tools	Claude Code, Codex CLI, OpenCode, OpenClaw
Letta Code SDK	TypeScript only	Same agent harness as Letta Code, but accessible via TypeScript	Claude Agent SDK
Letta API	TypeScript, Python, or REST	A stateful LLM API that connects memory to any model provider	OpenAI Responses API