Letta Code SDK quickstart

Installation

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

Quick start

One-shot prompt

import { prompt } from "@letta-ai/letta-code-sdk";

const result = await prompt("What is 2 + 2?");
console.log(result.result);

Multi-turn session

import { createAgent, resumeSession } from "@letta-ai/letta-code-sdk";

const agentId = await createAgent();
await using session = resumeSession(agentId);

await session.send("What is 5 + 3?");
for await (const msg of session.stream()) {
  if (msg.type === "assistant") console.log(msg.content);
}

Concepts

• Agent (agentId): A persistent entity with memory.
• Conversation (conversationId): A message thread within an agent.
• Session: A single execution/connection.
• Default conversation: Always exists after createAgent(); use resumeSession(agentId).

Configuration

System prompt

createSession(agentId, {
  systemPrompt: { type: "preset", preset: "letta-claude" },
});

createSession(agentId, {
  systemPrompt: { type: "preset", preset: "letta-claude", append: "Always respond in Spanish." },
});

createSession(agentId, {
  systemPrompt: "You are a helpful Python expert.",
});

Presets:

• default / letta-claude
• letta-codex
• letta-gemini
• claude, codex, gemini (minimal prompts)

Memory blocks

createSession(agentId, {
  memory: ["project", "persona"],
});

createSession(agentId, {
  memory: [
    { label: "context", value: "API docs for Acme Corp..." },
    { label: "rules", value: "Always use TypeScript." },
  ],
});

Tool execution

createSession(agentId, {
  allowedTools: ["Glob", "Bash"],
  permissionMode: "bypassPermissions",
  cwd: "/path/to/project",
});

API reference

Functions

Function	Description
createAgent()	Create a new agent with a default conversation
createSession()	New conversation on default agent
createSession(agentId)	New conversation on specified agent
resumeSession(id)	Resume session (pass agent-xxx or conv-xxx)
prompt(message)	One-shot query with default agent
prompt(message, agentId)	One-shot query with specific agent

Session

Property/Method	Description
send(message)	Send user message
stream()	Async generator yielding messages
close()	Close the session
agentId	Agent ID
sessionId	Current session ID
conversationId	Conversation ID

Options

interface SessionOptions {
  model?: string;
  systemPrompt?: string | { type: "preset"; preset: string; append?: string };
  memory?: Array<string | CreateBlock | { blockId: string }>;
  persona?: string;
  human?: string;
  project?: string;
  cwd?: string;

  allowedTools?: string[];
  permissionMode?: "default" | "acceptEdits" | "bypassPermissions";
  canUseTool?: (toolName: string, toolInput: object) => Promise<CanUseToolResponse>;
  maxTurns?: number;
}