How does one password work with private spaces in the newest Android release?

Hi dmbulfer. Great question, actually. For anyone not familiar with the Private Space feature introduced with Android 15, you can read about it here.

The way the Private Space works under the hood is by creating a completely separate user on your device. Support for multiple users has existed in different forms since Android 11. What's new in Android 15 is that apps installed as this "secondary" user are now visible in the "primary" user's app launcher and system settings. (This is actually pretty similar to how Samsung's Secure Folder has worked for awhile now.) What this means is that apps that typically use Android APIs to communicate with each other (such as 1Password providing autofill services to Chrome) can do so, but are not allowed to cross this "user" boundary. This OS compartmentalization is the main security feature of Private Space.

So, as you surmised, you can definitely install the 1Password app into the Private Space (or Secure Folder), but autofill will only work with other apps installed in the Private Space. The clipboard is shared between compartments, however, so you could still copy information from an app installed in the Private Space and paste it into an app installed in the "normal" space if you really wanted to.