[Python] Playwright Python: Session Cookies Not Persisting in `launch_persistent_context` -...

I'm using Playwright for Python with launch_persistent_context to create a persistent browser context that should retain cookies across browser launches. However, I've noticed that session cookies (those without an Expires or Max-Age attribute) do not persist when relaunching the context, while cookies with an explicit Expires attribute do persist. Is this expected behavior, or is it a bug in Playwright?

Code Example


Below is a simplified test script that demonstrates the issue:

import os
import shutil
from datetime import datetime, timedelta

from playwright.sync_api import sync_playwright


def test_persistent_cookies():
user_data_dir = './user_data'
if os.path.exists(user_data_dir):
shutil.rmtree(user_data_dir)

with sync_playwright() as p:
# First launch: Set a session cookie and a non-session cookie
context = p.chromium.launch_persistent_context(
user_data_dir, headless=True
)
page = context.new_page()
page.goto('https://example.com')

# Session cookie (no expires)
session_cookie = {
'name': 'session_cookie',
'value': 'session_value_123',
'domain': 'example.com',
'path': '/',
'httpOnly': False,
'secure': False,
'sameSite': 'Lax',
}

# Non-session cookie (with expires)
future_time = int((datetime.now() + timedelta(days=1)).timestamp())
persistent_cookie = {
'name': 'persistent_cookie',
'value': 'persistent_value_456',
'domain': 'example.com',
'path': '/',
'expires': future_time,
'httpOnly': False,
'secure': False,
'sameSite': 'Lax',
}

context.add_cookies([session_cookie, persistent_cookie])

# Verify cookies in first session
cookies = context.cookies()
cookie_names = [cookie['name'] for cookie in cookies]
print('First session cookies:', cookie_names)

assert 'session_cookie' in cookie_names, 'Session cookie not set'
assert 'persistent_cookie' in cookie_names, 'Persistent cookie not set'

context.close()

# Second launch: Check cookie persistence
context2 = p.chromium.launch_persistent_context(
user_data_dir, headless=True
)
cookies = context2.cookies()
cookie_names = [cookie['name'] for cookie in cookies]
print('Second session cookies:', cookie_names)

if 'session_cookie' not in cookie_names:
print('BUG: Session cookie did not persist in second session')

assert 'persistent_cookie' in cookie_names, (
'Persistent cookie did not persist'
)

context2.close()
shutil.rmtree(user_data_dir)


if __name__ == '__main__':
test_persistent_cookies()

Observed Behavior


$ .../.venv/Scripts/python.exe .../~scratch.py
First session cookies: ['session_cookie', 'persistent_cookie']
Second session cookies: ['persistent_cookie']
BUG: Session cookie did not persist in second session
Test completed!


The session cookie (session_cookie) is present in the first session but missing in the second session. The non-session cookie (persistent_cookie) persists correctly across both sessions.

Expected Behavior


Since launch_persistent_context uses a user data directory to store browser data, I expect both session and non-session cookies to persist across browser launches, as the user data directory should retain all cookies set in the context.

Environment

• Playwright Version: 1.52.0
• Python Version: 3.13.3
• Operating System: Windows (both 10 and 11)
• Browser: Chromium (headless or non-headless)

Additional Context


The script uses context.add_cookies() to set cookies, but I get the same result when cookies are set via a page interaction (e.g., JavaScript).

I’ve ensured the user data directory is clean before each run to avoid interference.

The Playwright documentation doesn’t explicitly state whether session cookies should persist in a persistent context, but the mention of "browser session data like cookies" suggests they should.

I’m aware that using context.storage_state() can persist session cookies by saving and loading the state, but I prefer launch_persistent_context because it retains cached content like JavaScript and CSS files, avoiding redownloads and improving performance.

Any insights into whether this is intended behavior or a bug, and potential workarounds, would be greatly appreciated! Should I file a bug report with the Playwright team?

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