My Key File is not auto detected in AutoFill mode

This is a bit of a weird edge case. Assuming the key file is stored in the Strongbox documents folder… Apple does not allow App Extensions (which is what Auto Fill is) to access the parent App’s documents directory directly. This leads to the situation where Strongbox can see the key file (and use it automatically) but not the App Extension (Auto Fill).

The solution to this is to “Import” your Key File instead of leaving it in Strongbox’s Documents directory. You can do this via “Key File Management”. This can be accessed during the Unlock screen or by going to Preferences (Gear icon in the top right corner).

There’s another quick fix/work around, which is to use a PIN code or Biometric (Touch ID/Face ID) convenience method to open your database, this means Strongbox can use master credentials stored in the secure enclave (which is also accessible by the Auto Fill extension).