What does your feature entail? What is it for? How will it affect existing workflows or user experience?
'Safari keychain' (or 'Safari passwords') would seem to be a more accurate description than the '3rd party provider' in the popup button for the behaviour I've seen.
Secondary text (the dimmed kind) that explains the slight UX differences (e.g. 'Passwords can be auto-filled after authenticating and selecting the correct entry in the list'), as well as the nature of the different sources of password data, updated upon selection in the popup button, could also be helpful.
What are the exact ways that you see a user using your proposed feature? Please go into as much detail as possible, and provide examples of how other browsers/apps implement this feature, if applicable. If your feature suggestion adds on to an existing feature, how would it work into it to extend its usefulness?
I'm getting a great initial impression of Orion.
One big challenge for me when adopting a new browser is the aspect of working with my saved passwords. I've found that I couldn't swallow a password migration strategy as suggested by Orion, since I can't commit to switching to Orion for both my Mac and my iPhone at the same time, so would like to keep working with the passwords thus far managed by Safari, yet still use Orion without too much friction on my Mac. I.e. I want to use Orion on Mac, Safari on iPhone, and not struggle with passwords.
I found that when the password provider is set to '3rd party provider', username / password text fields are given the option to view passwords (via 'Passwords...' menu item), which allows me to choose the password to autofill after authenticating with Touch ID. This is a few more steps than autofilling passwords immediately at the text fields, but certainly much better than no access to Safari passwords at login time. I was pleasantly surprised to find this level of integration with Safari-managed passwords, since the explanation during on-boarding and various wordings around password management / autofill gave me the impression I'd need to import the passwords during on-boarding, then have Orion manage its own list of passwords, along with the annoyance of it going out of step with the Safari passwords.
Of course, having Safari password autofill candidates show up at the credential text fields would be the best solution, but I'm guessing the current design reflects API limitations.