Letta Agent Sdk

Letta Agent SDK

[](https://www.npmjs.com/package/@letta-ai/letta-agent-sdk) [](https://discord.gg/letta)

The SDK for [stateful agents](https://docs.letta.com/concepts/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](https://docs.letta.com/agent-sdk) 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);
}

Latency-sensitive applications can initialize the runtime and transport before the first user action without fetching transcript history or invoking the model:

const session = client.resumeSession(conversationId);
await session.ready();
await session.send(message);

`ready()` is idempotent and safe to call concurrently. `SDKResultMessage.durationMs` measures the tracked turn and excludes session initialization; measure `ready()` separately when startup latency matters.

Set `LETTA_API_KEY` for the cloud backend. See the [quickstart](https://docs.letta.com/agent-sdk/quickstart) for the local and self-hosted paths.

Where your agents run

One interface, t