Following the update from macOS 26.6 > 27.0, MAMP Pro — while still able to render front-end WordPress pages — threw server errors when trying to access admin pages.
An email to MAMP Pro support resulted in the following email:
Thank you for your message. This matches a known issue on macOS 27 — Apache/FastCGI crashes on fork for requests that touch wp-admin/wp-login, while static front-end pages are unaffected. We now have a workaround while the permanent fix is finished:
1. Quit MAMP PRO.
2. Open /Applications/MAMP/fcgi-bin in Finder.
3. For each php#.#.#.fcgi file you use, open it in a text editor and add this line near the top: export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
4. Save and restart MAMP PRO.A couple of notes: this disables a macOS safety check rather than fixing the underlying cause, so it’s a temporary workaround, not the official fix — please back up the file first. If you add a new PHP version later, you’ll need to repeat step 3 for it. A permanent fix is still on track for an upcoming release, expected later in October 2026.
This worked great. Took all of 10 seconds in BBEdit.
It was, however, still necessary to toggle WordPress > Admin > Settings > Permalinks to another value then revert it, as most Pages & Posts were 404’ing after fixing.