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Work with sessions

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Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt Use this file to discover all available pages before exploring further.

Work with sessions

How sessions persist agent conversation history, and when to use continue, resume, and fork to return to a prior run.

A session is the conversation history the SDK accumulates while your agent works. It contains your prompt, every tool call the agent made, every tool result, and every response. The SDK writes it to disk automatically so you can return to it later.

Returning to a session means the agent has full context from before: files it already read, analysis it already performed, decisions it already made. You can ask a follow-up question, recover from an interruption, or branch off to try a different approach.

Sessions persist the conversation, not the filesystem. To snapshot and revert file changes the agent made, use file checkpointing.

This guide covers how to pick the right approach for your app, the SDK interfaces that track sessions automatically, how to capture session IDs and use resume and fork manually, and what to know about resuming sessions across hosts.

Choose an approach

How much session handling you need depends on your application's shape. Session management comes into play when you send multiple prompts that should share context. Within a single query() call, the agent already takes as many turns as it needs, and permission prompts and AskUserQuestion are handled in-loop (they don't end the call).

What you're building What to use
One-shot task: single prompt, no follow-up Nothing extra. One query() call handles it.
Multi-turn chat in one process ClaudeSDKClient (Python) or continue: true (TypeScript). The SDK tracks the session for you with no ID handling.
Pick up where you left off after a process restart continue_conversation=True (Python) / continue: true (TypeScript). Resumes the most recent session in the directory, no ID needed.
Resume a specific past session (not the most recent) Capture the session ID and pass it to resume.
Try an alternative approach without losing the original Fork the session.
Stateless task, don't want anything written to disk (TypeScript only) Set persistSession: false. The session exists only in memory for the duration of the call. Python always persists to disk.

Continue, resume, and fork

Continue, resume, and fork are option fields you set on query() (ClaudeAgentOptions in Python, Options in TypeScript).

Continue and resume both pick up an existing session and add to it. The difference is how they find that session:

Fork is different: it creates a new session that starts with a copy of the original's history. The original stays unchanged. Use fork to try a different direction while keeping the option to go back.

Automatic session management

Both SDKs offer an interface that tracks session state for you across calls, so you don't pass IDs around manually. Use these for multi-turn conversations within a single process.

Python: ClaudeSDKClient

ClaudeSDKClient handles session IDs internally. Each call to client.query() automatically continues the same session. Call client.receive_response() to iterate over the messages for the current query. The client must be used as an async context manager.

This example runs two queries against the same client. The first asks the agent to analyze a module; the second asks it to refactor that module. Because both calls go through the same client instance, the second query has full context from the first without any explicit resume or session ID:

```python Python theme={null} import asyncio from claude_agent_sdk import ( ClaudeSDKClient, ClaudeAgentOptions, AssistantMessage, ResultMessage, TextBlock, )

def print_response(message): """Print only the human-readable parts of a message.""" if isinstance(message, AssistantMessage): for block in message.content: if isinstance(block, TextBlock): print(block.text) elif isinstance(message, ResultMessage): cost = ( f"${message.total_cost_usd:.4f}" if message.total_cost_usd is not None else "N/A" ) print(f"[done: {message.subtype}, cost: {cost}]")

async def main(): options = ClaudeAgentOptions( allowed_tools=["Read", "Edit", "Glob", "Grep"], )

async with ClaudeSDKClient(options=options) as client:
    # First query: client captures the session ID internally
    await client.query("Analyze the auth module")
    async for message in client.receive_response():
        print_response(message)

    # Second query: automatically continues the same session
    await client.query("Now refactor it to use JWT")
    async for message in client.receive_response():
        print_response(message)

asyncio.run(main())


See the [Python SDK reference](https://code.claude.com/en/agent-sdk/python#choosing-between-query-and-claude-sdk-client) for details on when to use `ClaudeSDKClient` vs the standalone `query()` function.

### TypeScript: `continue: true`

The stable TypeScript SDK (the `query()` function used throughout these docs, sometimes called V1) doesn't have a session-holding client object like Python's `ClaudeSDKClient`. Instead, pass `continue: true` on each subsequent `query()` call and the SDK picks up the most recent session in the current directory. No ID tracking required.

This example makes two separate `query()` calls. The first creates a fresh session; the second sets `continue: true`, which tells the SDK to find and resume the most recent session on disk. The agent has full context from the first call:

```typescript TypeScript theme={null}
import { query } from "@anthropic-ai/claude-agent-sdk";

// First query: creates a new session
for await (const message of query({
  prompt: "Analyze the auth module",
  options: { allowedTools: ["Read", "Glob", "Grep"] }
})) {
  if (message.type === "result" && message.subtype === "success") {
    console.log(message.result);
  }
}

// Second query: continue: true resumes the most recent session
for await (const message of query({
  prompt: "Now refactor it to use JWT",
  options: {
    continue: true,
    allowedTools: ["Read", "Edit", "Write", "Glob", "Grep"]
  }
})) {
  if (message.type === "result" && message.subtype === "success") {
    console.log(message.result);
  }
}

There's also a V2 preview of the TypeScript SDK that provides createSession() with a send / stream pattern, closer to Python's ClaudeSDKClient in feel. V2 is unstable and its APIs may change; the rest of this documentation uses the stable V1 query() function.

Use session options with query()

Capture the session ID

Resume and fork require a session ID. Read it from the session_id field on the result message (ResultMessage in Python, SDKResultMessage in TypeScript), which is present on every result regardless of success or error. In TypeScript the ID is also available earlier as a direct field on the init SystemMessage; in Python it's nested inside SystemMessage.data.

```python Python theme={null} import asyncio from claude_agent_sdk import query, ClaudeAgentOptions, ResultMessage

async def main(): session_id = None

  async for message in query(
      prompt="Analyze the auth module and suggest improvements",
      options=ClaudeAgentOptions(
          allowed_tools=["Read", "Glob", "Grep"],
      ),
  ):
      if isinstance(message, ResultMessage):
          session_id = message.session_id
          if message.subtype == "success":
              print(message.result)

  print(f"Session ID: {session_id}")
  return session_id

session_id = asyncio.run(main()) ```

```typescript TypeScript theme={null} import { query } from "@anthropic-ai/claude-agent-sdk";

let sessionId: string | undefined;

for await (const message of query({ prompt: "Analyze the auth module and suggest improvements", options: { allowedTools: ["Read", "Glob", "Grep"] } })) { if (message.type === "result") { sessionId = message.session_id; if (message.subtype === "success") { console.log(message.result); } } }

console.log(Session ID: ${sessionId}); ```

Resume by ID

Pass a session ID to resume to return to that specific session. The agent picks up with full context from wherever the session left off. Common reasons to resume:

This example resumes the session from Capture the session ID with a follow-up prompt. Because you're resuming, the agent already has the prior analysis in context:

python Python theme={null} # Earlier session analyzed the code; now build on that analysis async for message in query( prompt="Now implement the refactoring you suggested", options=ClaudeAgentOptions( resume=session_id, allowed_tools=["Read", "Edit", "Write", "Glob", "Grep"], ), ): if isinstance(message, ResultMessage) and message.subtype == "success": print(message.result)

typescript TypeScript theme={null} // Earlier session analyzed the code; now build on that analysis for await (const message of query({ prompt: "Now implement the refactoring you suggested", options: { resume: sessionId, allowedTools: ["Read", "Edit", "Write", "Glob", "Grep"] } })) { if (message.type === "result" && message.subtype === "success") { console.log(message.result); } }

If a resume call returns a fresh session instead of the expected history, the most common cause is a mismatched cwd. Sessions are stored under ~/.claude/projects/<encoded-cwd>/*.jsonl, where <encoded-cwd> is the absolute working directory with every non-alphanumeric character replaced by - (so /Users/me/proj becomes -Users-me-proj). If your resume call runs from a different directory, the SDK looks in the wrong place. The session file also needs to exist on the current machine.

Fork to explore alternatives

Forking creates a new session that starts with a copy of the original's history but diverges from that point. The fork gets its own session ID; the original's ID and history stay unchanged. You end up with two independent sessions you can resume separately.

Forking branches the conversation history, not the filesystem. If a forked agent edits files, those changes are real and visible to any session working in the same directory. To branch and revert file changes, use file checkpointing.

This example builds on Capture the session ID: you've already analyzed an auth module in session_id and want to explore OAuth2 without losing the JWT-focused thread. The first block forks the session and captures the fork's ID (forked_id); the second block resumes the original session_id to continue down the JWT path. You now have two session IDs pointing at two separate histories:

```python Python theme={null} # Fork: branch from session_id into a new session forked_id = None async for message in query( prompt="Instead of JWT, implement OAuth2 for the auth module", options=ClaudeAgentOptions( resume=session_id, fork_session=True, ), ): if isinstance(message, ResultMessage): forked_id = message.session_id # The fork's ID, distinct from session_id if message.subtype == "success": print(message.result)

print(f"Forked session: {forked_id}")

# Original session is untouched; resuming it continues the JWT thread async for message in query( prompt="Continue with the JWT approach", options=ClaudeAgentOptions(resume=session_id), ): if isinstance(message, ResultMessage) and message.subtype == "success": print(message.result) ```

```typescript TypeScript theme={null} // Fork: branch from sessionId into a new session let forkedId: string | undefined;

for await (const message of query({ prompt: "Instead of JWT, implement OAuth2 for the auth module", options: { resume: sessionId, forkSession: true } })) { if (message.type === "system" && message.subtype === "init") { forkedId = message.session_id; // The fork's ID, distinct from sessionId } if (message.type === "result" && message.subtype === "success") { console.log(message.result); } }

console.log(Forked session: ${forkedId});

// Original session is untouched; resuming it continues the JWT thread for await (const message of query({ prompt: "Continue with the JWT approach", options: { resume: sessionId } })) { if (message.type === "result" && message.subtype === "success") { console.log(message.result); } } ```

Resume across hosts

Session files are local to the machine that created them. To resume a session on a different host (CI workers, ephemeral containers, serverless), you have two options:

Both SDKs expose functions for enumerating sessions on disk and reading their messages: listSessions() and getSessionMessages() in TypeScript, list_sessions() and get_session_messages() in Python. Use them to build custom session pickers, cleanup logic, or transcript viewers.

Both SDKs also expose functions for looking up and mutating individual sessions: get_session_info(), rename_session(), and tag_session() in Python, and getSessionInfo(), renameSession(), and tagSession() in TypeScript. Use them to organize sessions by tag or give them human-readable titles.