On iOS for passwords, this is a systemwide system that allows any app to register as a password provider and any password field to receive those passwords via t

On iOS for passwords, this is a systemwide system that allows any app to register as a password provider and any password field to receive those passwords via the system keyboard. I would assume that the system passkey interface will handle the receiving app, and the sharing app will register with the system (NOT with the browser or app, although this doesn't preclude doing that as well) to vend passkeys.