Is there a version of the 1Password Extension available via Apple's Extension Download that will work with Safari 9 Build 1? I know that it is new ground, so I am just pondering this, not expecting.
Secure Extensions Distribution introduces improved security for Safari on OS X. All extensions in the Safari Extensions Gallery are now hosted and signed by Apple. Users can trust that the Safari Extension they install is the one you submitted.
Only Safari Extensions installed from the Safari Extensions Gallery can be updated automatically. Add the following two lines to each extension's dictionary entry within your Update Manifest to allow existing users to update automatically to the latest version.
1Password Version: 5.3
Extension Version: 4.3.1
OS Version: 10.10.4 (14E36b)
Sync Type: iCloud