Chrome 136+ ignores remote debugging on the default profile: a scheduled job needs a separate user-data-dir

What was planned

A daily Task Scheduler job on Windows was to open a web console in the user's everyday Chrome profile, reuse the existing sign-in, and read some page data with Playwright (or a similar tool that drives Chrome through the DevTools protocol).

Why it cannot work as written

Since Chrome 136 the browser ignores the --remote-debugging-port and --remote-debugging-pipe switches when Chrome is using its default user data directory. The documented purpose is to stop other software from reaching the everyday profile's cookies through the debugging port. An automation tool that launches or attaches to Chrome on the default profile therefore finds no debugging endpoint. The design session summarised this as "Chrome refuses automation on its default profile".

Copying the profile does not carry the sign-in

The session also noted that copying the profile folder elsewhere does not preserve the sign-in, because Chrome encrypts cookies so that only Chrome itself can read them. This is the session's statement; the mechanism behind it (Chrome's cookie encryption tied to the original profile and Windows user) was not examined or reproduced, and it is not in the Chrome announcement above.

Options that were considered

• A separate, non-default profile. Start Chrome with --user-data-dir=<a dedicated folder> (a non-default directory is what makes the remote-debugging switches work again), sign in to the site once in that profile by hand, and let the scheduled job reuse that profile. The job runs only while the user is logged on, as the original plan assumed. This is the route Chrome documents for automation.
• A small browser extension in the everyday profile. The extension, loaded manually in the normal browser, reads the page data once a day while Chrome is open and uploads it, so no scheduler and no stored password are involved. The trade-off recorded was dependence on the site's internal, undocumented data endpoints, which can change without notice; a failure was made visible with an error badge and a "last updated" age warning.

The session built the extension. The separate-profile route was not tried in the sources, so details such as session expiry in the dedicated profile are unobserved.

Unverified

• The exact Chrome version in use and its policy settings were not recorded.
• Whether a managed (enterprise) policy can re-enable the switches on the default profile was not checked.