Browser and React Native

Use the portable /client entry point in browser, Expo, and React Native applications. It includes the cloud and remote transports without importing Node process-management modules:

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

const client = new LettaAgentClient({
  backend: "cloud",
  apiKey: userProvidedApiKey,
  webSocketAuth: "query",
});

What the portable entry supports

Capability	Portable /client entry	Node package root
backend: "cloud"	✅	✅
backend: "remote"	✅	✅
backend: "local"	❌	✅
MCP servers (mcpServers)	❌	✅
Client tools (tools)	✅	✅
Repositories (client.repositories)	✅	✅
imageFromFile helper	❌ (use imageFromBase64)	✅

Import from the package root in Node.js when you need backend: "local", which starts and manages a local App Server subprocess, or MCP servers, which run in the SDK’s Node process.

Browser authentication

Browser WebSockets cannot set upgrade headers, so cloud clients in the browser should use webSocketAuth: "query" to send credentials in the connection URL instead:

const client = new LettaAgentClient({
  backend: "cloud",
  apiKey: userProvidedApiKey,
  webSocketAuth: "query",
});

An API key shipped to the browser is visible to the user. Issue short-lived, user-scoped credentials from your backend rather than embedding an organization-wide key in client code.

React Native

For an authenticated remote App Server in React Native, adapt the platform WebSocket constructor so the SDK can pass the Authorization header:

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

const client = new LettaAgentClient({
  backend: "remote",
  url: appServerUrl,
  authToken: appServerToken,
  WebSocket: createReactNativeWebSocketConstructor(WebSocket),
});

Sending messages from portable clients

Sessions work the same as in Node: create or resume a session, send, and stream. See Sending messages for the full event-handling patterns.

await using session = client.resumeSession(agentId);

await session.send("Summarize my unread updates.");

for await (const message of session.stream()) {
  if (message.type === "assistant") process.stdout.write(message.content);
}

For images, use imageFromBase64 or imageFromURL; the file-reading helper is Node-only.