Fixing the “Route update.module_install does not exist” Error After Upgrading Drupal 10.3 to 10.4

Fixing the “Route update.module_install does not exist” Error After Upgrading Drupal 10.3 to 10.4

Recently, I upgraded one of my Drupal projects from Drupal 10.3 to 10.4 along with all contributed modules. After the update, I hit a frustrating error:

    Route "update.module_install" does not exist

At first, I thought it was a compatibility issue with contributed modules or a routing change in Drupal 10.4. I cleared caches, rebuilt the router, and even double-checked whether the Update Manager module (update) was enabled—but the error persisted.

The Real Cause

The issue wasn’t in Drupal core or the modules at all. The problem was in how I uploaded the updated files.

I had been using cPanel to upload the new Drupal 10.4 files. My initial approach was to simply overwrite the old Drupal files with the new ones. However, this left behind some old files that no longer exist in 10.4, which caused conflicts and missing routes.

The Solution

The fix was simple once I realized the mistake:

1. Deleted all old Drupal core files (except for the sites folder and any custom modules/themes).

2. Uploaded the fresh Drupal 10.4 files via cPanel.

3. Ran the standard update script:

4. Cleared caches with Drush or the admin UI.

After doing this, the update completed successfully and the error disappeared.

Key Takeaway

When upgrading Drupal (or any CMS), don’t just overwrite files. Always remove the old core files before uploading the new version. Overwriting can leave behind obsolete files that cause strange issues, like missing routes.

If you’re updating via cPanel or FTP, the safest process is:

• Backup everything first (database + files).

• Delete old core files (except sites/).

• Upload the fresh core version.

• Run update.php and clear caches.