No there's no public available API and AFAIK there are no plans for that.
Thank you for letting me know!
Official API client used by proton: https://github.com/ProtonMail/go-proton-api
I didn't see any good documentation. Its in use by (or has at least inspired) https://github.com/henrybear327/Proton-API-Bridge?tab=readme-ov-file
The API bridge backs rclone's Proton Drive support.
What's caldav and carddav used for?
Usually sync calendar and contacts.
Proto calendar does have an ics thing. Maybe you can use drive to backup your contacts
Not there. But would be great. At least a way to backup and recover your contacts to a new phone (both Android and iOS). That would be awesome.
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