Letta Agent SDK

The SDK for stateful agents: create an agent once, then resume it from anywhere. Each agent has its own identity and long-term memory, and keeps both across conversations, models, and the computers it runs on.

Read the documentation for guides and the full API reference.

Quick start

npm install @letta-ai/letta-agent-sdk

import { LettaAgentClient } from "@letta-ai/letta-agent-sdk";

const client = new LettaAgentClient({ backend: "cloud" });

// Create the agent once...
const agentId = await client.createAgent({
  systemPrompt: "You are Nora, a research analyst who tracks our competitors.",
  memfs: true,
});

// ...then resume it, from anywhere, for as long as it lives.
await using session = client.resumeSession(agentId);

await session.send("What changed since last week?");
for await (const message of session.stream()) {
  if (message.type === "assistant") process.stdout.write(message.content);
}

Set LETTA_API_KEY for the cloud backend. See the quickstart for the local and self-hosted paths.

Where your agents run

One interface, three backends:

Backend	Agent state	Tools execute
"cloud"	Hosted by Letta	A managed sandbox, or a computer you connect
"local"	On this machine*	On this machine*
"remote"	Your App Server	On your App Server machine

* "this machine" refers to the machine that the SDK code itself is running on

Browser, Expo, and React Native applications import from @letta-ai/letta-agent-sdk/client, which does not require Node and supports the cloud and remote backends. See Deployment.

Examples

Runnable applications live in examples/. Start with the examples guide, which orders the demos by concept and lists their setup and side effects. See the React chat template for a more complete custom UI.

Contributing

Development conventions for this repository are in AGENTS.md.

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