Claude Cookbook
Claude Agent SDKAgent Patterns
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Building a session browser

List, read, rename, tag, and fork Agent SDK sessions on disk to build a conversation history sidebar without writing a transcript parser.

Qing Wang
Qing Wang
@qing-ant
Published on March 30, 2026
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Building a Session Browser

When you ship an agent as a product (a desktop app, an IDE extension, an internal chatbot), the first thing users ask for is the sidebar. They want to see the conversation from last Tuesday, jump back into it, and maybe branch off in a new direction without losing the original. The agent loop is half the product; the other half is session management.

The Claude Agent SDK writes every conversation to a JSONL transcript on disk. It also ships a set of functions that read those transcripts back and organize them, so you can build that sidebar without writing a file parser or walking ~/.claude/projects/ by hand.

By the end of this cookbook, you'll be able to:

  • List and render past sessions for a project, with pagination and metadata like branch, title, and last-modified time
  • Read a stored session's messages back into your UI without spawning the agent
  • Rename, tag, and filter sessions so users can organize their history
  • Fork a session at any point and resume the fork as a live query() call

This is the pattern behind the session sidebar in Claude Code Desktop and the VS Code extension. The same primitives work for any UI you want to put on top of the Agent SDK.

Prerequisites

Before following this guide, ensure you have:

Required Knowledge

  • Python fundamentals, including async/await
  • Basic familiarity with the Agent SDK's query() function (see Notebook 00(opens in new tab) for an introduction)

Required Tools

Setup

Install the required dependencies. Session management functions landed in claude-agent-sdk v0.1.51.

%%capture
%pip install -U "claude-agent-sdk>=0.1.51" python-dotenv pandas

Load your API key from .env and configure the model. We use Haiku here because the demo sessions are short and we want them cheap and fast; in a real product you'd pick whatever model fits your agent.

import os
from pathlib import Path
from dotenv import load_dotenv
load_dotenv()
MODEL = "claude-haiku-4-5"
# All demo sessions live under this project directory. Using a dedicated
# cwd keeps the demo isolated from your real Claude Code sessions.
# Note: this path resolves relative to the kernel's working directory
# (claude_agent_sdk/ when launched per the README).
DEMO_DIR = str(Path("session_browser_demo").resolve())
os.makedirs(DEMO_DIR, exist_ok=True)
print(f"Demo project dir: {DEMO_DIR}")

Part 1: Create some sessions to manage

Session management functions read transcripts that query() (or the Claude Code CLI) has already written. To have something to browse, we first run three short conversations and capture their session IDs.

The cwd option tells the SDK which project directory this conversation belongs to. Transcripts are filed under ~/.claude/projects/<encoded-cwd>/<session-id>.jsonl, so every call with the same cwd ends up in the same bucket. That bucket is what list_sessions(directory=...) reads later.

We disable tools and cap each run at one turn to keep token usage minimal.

from claude_agent_sdk import ClaudeAgentOptions, ResultMessage, query
async def run_one_turn(prompt: str) -> str:
"""Run a single-turn conversation and return its session_id."""
opts = ClaudeAgentOptions(
model=MODEL,
cwd=DEMO_DIR,
max_turns=1,
allowed_tools=[], # text-only, no tool loop
)
session_id = None
async for msg in query(prompt=prompt, options=opts):
if isinstance(msg, ResultMessage):
session_id = msg.session_id
preview = (msg.result or "")[:80]
print(f"[{session_id[:8]}] {preview}...")
if session_id is None:
raise RuntimeError("No ResultMessage received; check API key and SDK version.")
return session_id

Three prompts, three sessions. In a real product these would be whatever your users asked the agent.

prompts = [
"Give me three name ideas for a CLI tool that manages git worktrees.",
"Explain the difference between a mutex and a semaphore in one paragraph.",
"Write a haiku about merge conflicts.",
]
demo_session_ids = []
for p in prompts:
sid = await run_one_turn(p)
demo_session_ids.append(sid)
print(f"\nCreated {len(demo_session_ids)} sessions.")

Part 2: List and inspect sessions

Build the session list

list_sessions() scans the project's transcript directory and returns metadata for each session, sorted newest first. It reads file stats plus the head and tail of each transcript, so it stays fast even when the directory has hundreds of files. No subprocess is spawned and no API call is made.

Each SDKSessionInfo carries what you need to render a row in a picker: a display summary, last-modified timestamp, git branch, working directory, and any custom title or tag you've set.

from datetime import datetime
import pandas as pd
from claude_agent_sdk import SDKSessionInfo, list_sessions
sessions = list_sessions(directory=DEMO_DIR)
# Render as a table. In a real UI this would be your sidebar component.
rows = []
for s in sessions:
rows.append(
{
"id": s.session_id[:8],
"summary": (s.summary[:50] + "...") if len(s.summary) > 50 else s.summary,
"modified": datetime.fromtimestamp(s.last_modified / 1000).strftime("%H:%M:%S"),
"branch": s.git_branch or "-",
"tag": s.tag or "-",
}
)
pd.DataFrame(rows)

For long histories, pass limit and offset to page through results. A session picker typically loads the first page, then fetches more as the user scrolls:

page_2 = list_sessions(directory=DEMO_DIR, limit=20, offset=20)

If your app already stored a session ID (say, in your own database alongside a user record) and you just need that one row, get_session_info() is cheaper than listing everything.

from claude_agent_sdk import get_session_info
info = get_session_info(demo_session_ids[0], directory=DEMO_DIR)
print(f"Session: {info.session_id}")
print(f"Summary: {info.summary}")
print(f"First prompt: {info.first_prompt}")
print(f"Created: {datetime.fromtimestamp(info.created_at / 1000)}")
print(f"Size: {info.file_size:,} bytes")

Read a session's messages

Once a user clicks a session in the sidebar, you load its conversation into the main view. get_session_messages() reconstructs the message chain from the transcript and returns user and assistant turns in order. Like the listing function, it's a pure file read: the agent doesn't need to be running.

Each SessionMessage has a type ("user" or "assistant"), a uuid, and a message dict in the same shape as the Anthropic Messages API (role, content).

from claude_agent_sdk import get_session_messages
messages = get_session_messages(demo_session_ids[0], directory=DEMO_DIR)
for m in messages:
role = m.type
# content is a list of blocks; pull out the text ones
text_parts = [
b.get("text", "")
for b in m.message.get("content", [])
if isinstance(b, dict) and b.get("type") == "text"
]
text = " ".join(text_parts).strip()
print(f"[{role:>9}] {text[:100]}")

For long sessions, limit and offset let you load a window at a time. A chat view might load the last 50 messages on open, then fetch older pages as the user scrolls up. Offsets are applied in chronological order (oldest first), so page 0 is the start of the conversation.

Part 3: Organize with titles and tags

Rename a session

Auto-generated summaries are fine for a quick glance, but users often want to give a session a real name. rename_session() appends a title entry to the transcript; list_sessions() picks it up as custom_title on the next read.

Appends are cheap and idempotent: calling rename twice just means the newer title wins. No file rewrite happens.

from claude_agent_sdk import rename_session
rename_session(demo_session_ids[0], "Worktree CLI naming brainstorm", directory=DEMO_DIR)
rename_session(demo_session_ids[2], "Haiku corner", directory=DEMO_DIR)
# Verify the titles stuck
for s in list_sessions(directory=DEMO_DIR):
label = s.custom_title or "(auto)"
print(f"{s.session_id[:8]} custom_title={label!r} summary={s.summary[:40]!r}")

Tag and filter

Tags are a single string attached to a session. Use them for whatever categorization your product needs: "archived", "needs-review", "favorite". Pass None to clear a tag.

A common pattern is soft-delete: instead of removing the transcript file, tag it "__hidden" and filter that out in your list view. The data stays recoverable.

from claude_agent_sdk import tag_session
# Mark two sessions as favorites, hide the other
tag_session(demo_session_ids[0], "favorite", directory=DEMO_DIR)
tag_session(demo_session_ids[2], "favorite", directory=DEMO_DIR)
tag_session(demo_session_ids[1], "__hidden", directory=DEMO_DIR)
def visible_sessions(directory: str, tag_filter: str | None = None) -> list[SDKSessionInfo]:
"""List sessions, hiding soft-deletes and optionally filtering by tag."""
results = []
for s in list_sessions(directory=directory):
if s.tag == "__hidden":
continue
if tag_filter is not None and s.tag != tag_filter:
continue
results.append(s)
return results
favorites = visible_sessions(DEMO_DIR, tag_filter="favorite")
print(f"Visible favorites: {len(favorites)}")
for s in favorites:
print(f" {s.session_id[:8]} [{s.tag}] {s.custom_title or s.summary}")

Tags are single values, not lists. If you need multiple axes (say, a status plus a category), encode them into one string like "review:urgent" and parse on read, or store richer state in your own database keyed on session_id.

Part 4: Fork and resume

Branch from an existing conversation

Forking copies a session's transcript into a new file with freshly remapped message IDs. The original stays untouched. This is the primitive behind "try a different approach" features: the user keeps their original thread and gets a new one to experiment in.

fork_session() writes the new file and returns its ID. It doesn't run the agent, so the fork sits on disk until you resume it with query().

from claude_agent_sdk import fork_session
source = demo_session_ids[0]
fork = fork_session(
source,
directory=DEMO_DIR,
title="Worktree CLI names (round 2)",
)
print(f"Source: {source}")
print(f"Fork: {fork.session_id}")
# The fork starts with the same message history as the source
source_msgs = get_session_messages(source, directory=DEMO_DIR)
fork_msgs = get_session_messages(fork.session_id, directory=DEMO_DIR)
print(f"Source has {len(source_msgs)} messages, fork has {len(fork_msgs)}")

To branch from a specific point rather than the full history, pass up_to_message_id. The fork will contain the source transcript up to and including that message. You can get message UUIDs from get_session_messages()[i].uuid.

Resume the fork into a live query

The fork is just a transcript file. To turn it back into a running conversation, hand its ID to ClaudeAgentOptions.resume. The agent loads the forked history and continues from there.

resume_opts = ClaudeAgentOptions(
model=MODEL,
cwd=DEMO_DIR,
max_turns=1,
allowed_tools=[],
resume=fork.session_id,
)
async for msg in query(
prompt="Those were okay. Give me three more names, but punnier.",
options=resume_opts,
):
if isinstance(msg, ResultMessage):
print(f"[fork {fork.session_id[:8]} resumed]")
print(msg.result)

The original session is still sitting there unchanged. List again and you'll see both the source and the fork as separate rows with independent histories.

for s in list_sessions(directory=DEMO_DIR):
marker = "(fork)" if s.session_id == fork.session_id else " "
print(f"{marker} {s.session_id[:8]} {s.custom_title or s.summary[:50]}")

Cleanup

delete_session() removes a transcript file. It's a hard delete, which is why the soft-delete tag pattern from Part 3 is usually the safer default for user-facing UIs.

Here we use it to tidy up everything the demo created.

from claude_agent_sdk import delete_session
# Clean up every session in the demo dir, including the fork
for s in list_sessions(directory=DEMO_DIR):
delete_session(s.session_id, directory=DEMO_DIR)
print(f"Deleted {s.session_id[:8]}")
remaining = list_sessions(directory=DEMO_DIR)
print(f"\n{len(remaining)} session(s) remaining.")

Recap

We built the core of a session browser against the Agent SDK's local transcript store:

  • Listing with list_sessions() gives you everything needed to render a sidebar, and it scales because it reads file stats and head/tail slices rather than parsing whole transcripts.
  • Reading with get_session_messages() loads a conversation back for display without spawning the agent.
  • Organizing with rename_session() and tag_session() appends metadata entries, so it's cheap and the most recent call wins.
  • Forking with fork_session() plus options.resume lets users branch a conversation and keep going without touching the original.

All of these are pure file operations on ~/.claude/projects/. They work whether or not the agent subprocess is running, and they see the same transcripts the Claude Code CLI writes.

Where to go next

  • Wire it to a UI. These functions are UI-agnostic; drop them behind a FastAPI route or an Electron IPC handler and you have the backend for a session sidebar.
  • Cross-host sessions. Transcripts live on the local disk. To share sessions across machines, sync the files or index session IDs and messages into your own store. See Manage sessions on disk(opens in new tab) for patterns.
  • TypeScript. The same API exists in @anthropic-ai/claude-agent-sdk with camelCase names (listSessions, forkSession, and so on). See the TypeScript SDK reference(opens in new tab).
  • The bigger picture. Notebooks 00(opens in new tab) through 03(opens in new tab) cover building the agent itself. This notebook covers managing what it leaves behind.
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