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Documentation Index

Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt

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The V2 session API functions unstable_v2_createSession, unstable_v2_resumeSession, and unstable_v2_prompt are deprecated and will be removed in a future release. Use the V1 query() API instead.
V2 was an experimental session API that removed the need for async generators and yield coordination. Instead of managing generator state across turns, each turn was a separate send()/stream() cycle. The API surface reduced to three concepts:
  • createSession() / resumeSession(): Start or continue a conversation
  • session.send(): Send a message
  • session.stream(): Get the response

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Installation

The V2 interface is included in the existing SDK package: 
npm install @anthropic-ai/claude-agent-sdk
The SDK bundles a native Claude Code binary for your platform as an optional dependency, so you don’t need to install Claude Code separately.

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Quick start

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One-shot prompt

For simple single-turn queries where you don’t need to maintain a session, use unstable_v2_prompt(). This example sends a math question and logs the answer: 
import { unstable_v2_prompt } from "@anthropic-ai/claude-agent-sdk";

const result = await unstable_v2_prompt("What is 2 + 2?", {
  model: "claude-opus-4-7"
});
if (result.subtype === "success") {
  console.log(result.result);
}

​
Basic session

For interactions beyond a single prompt, create a session. V2 separates sending and streaming into distinct steps:
  • send() dispatches your message
  • stream() streams back the response
This explicit separation makes it easier to add logic between turns (like processing responses before sending follow-ups). The example below creates a session, sends “Hello!” to Claude, and prints the text response. It uses await using (TypeScript 5.2+) to automatically close the session when the block exits. You can also call session.close() manually. 
import { unstable_v2_createSession } from "@anthropic-ai/claude-agent-sdk";

await using session = unstable_v2_createSession({
  model: "claude-opus-4-7"
});

await session.send("Hello!");
for await (const msg of session.stream()) {
  // Filter for assistant messages to get human-readable output
  if (msg.type === "assistant") {
    const text = msg.message.content
      .filter((block) => block.type === "text")
      .map((block) => block.text)
      .join("");
    console.log(text);
  }
}

​
Multi-turn conversation

Sessions persist context across multiple exchanges. To continue a conversation, call send() again on the same session. Claude remembers the previous turns. This example asks a math question, then asks a follow-up that references the previous answer: 
import { unstable_v2_createSession } from "@anthropic-ai/claude-agent-sdk";

await using session = unstable_v2_createSession({
  model: "claude-opus-4-7"
});

// Turn 1
await session.send("What is 5 + 3?");
for await (const msg of session.stream()) {
  // Filter for assistant messages to get human-readable output
  if (msg.type === "assistant") {
    const text = msg.message.content
      .filter((block) => block.type === "text")
      .map((block) => block.text)
      .join("");
    console.log(text);
  }
}

// Turn 2
await session.send("Multiply that by 2");
for await (const msg of session.stream()) {
  if (msg.type === "assistant") {
    const text = msg.message.content
      .filter((block) => block.type === "text")
      .map((block) => block.text)
      .join("");
    console.log(text);
  }
}

​
Session resume

If you have a session ID from a previous interaction, you can resume it later. This is useful for long-running workflows or when you need to persist conversations across application restarts. This example creates a session, stores its ID, closes it, then resumes the conversation: 
import {
  unstable_v2_createSession,
  unstable_v2_resumeSession,
  type SDKMessage
} from "@anthropic-ai/claude-agent-sdk";

// Helper to extract text from assistant messages
function getAssistantText(msg: SDKMessage): string | null {
  if (msg.type !== "assistant") return null;
  return msg.message.content
    .filter((block) => block.type === "text")
    .map((block) => block.text)
    .join("");
}

// Create initial session and have a conversation
const session = unstable_v2_createSession({
  model: "claude-opus-4-7"
});

await session.send("Remember this number: 42");

// Get the session ID from any received message
let sessionId: string | undefined;
for await (const msg of session.stream()) {
  sessionId = msg.session_id;
  const text = getAssistantText(msg);
  if (text) console.log("Initial response:", text);
}

console.log("Session ID:", sessionId);
session.close();

// Later: resume the session using the stored ID
await using resumedSession = unstable_v2_resumeSession(sessionId!, {
  model: "claude-opus-4-7"
});

await resumedSession.send("What number did I ask you to remember?");
for await (const msg of resumedSession.stream()) {
  const text = getAssistantText(msg);
  if (text) console.log("Resumed response:", text);
}

​
Cleanup

Sessions can be closed manually or automatically using await using, a TypeScript 5.2+ feature for automatic resource cleanup. If you’re using an older TypeScript version or encounter compatibility issues, use manual cleanup instead. Automatic cleanup (TypeScript 5.2+): 
import { unstable_v2_createSession } from "@anthropic-ai/claude-agent-sdk";

await using session = unstable_v2_createSession({
  model: "claude-opus-4-7"
});
// Session closes automatically when the block exits
Manual cleanup: 
import { unstable_v2_createSession } from "@anthropic-ai/claude-agent-sdk";

const session = unstable_v2_createSession({
  model: "claude-opus-4-7"
});
// ... use the session ...
session.close();

​
API reference

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unstable_v2_createSession()

Creates a new session for multi-turn conversations. 
function unstable_v2_createSession(options: {
  model: string;
  // Additional options supported
}): SDKSession;

​
unstable_v2_resumeSession()

Resumes an existing session by ID. 
function unstable_v2_resumeSession(
  sessionId: string,
  options: {
    model: string;
    // Additional options supported
  }
): SDKSession;

​
unstable_v2_prompt()

One-shot convenience function for single-turn queries. 
function unstable_v2_prompt(
  prompt: string,
  options: {
    model: string;
    // Additional options supported
  }
): Promise<SDKResultMessage>;

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SDKSession interface

interface SDKSession {
  readonly sessionId: string;
  send(message: string | SDKUserMessage): Promise<void>;
  stream(): AsyncGenerator<SDKMessage, void>;
  close(): void;
}

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Feature availability

The V2 session API does not support every V1 feature. The following require the V1 SDK:
  • Session forking (forkSession option)
  • Some advanced streaming input patterns

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See also