Question 1

How do I sync Proton contacts to GrapheneOS?

Accepted Answer

AlpenSync is an Android sync client for Proton Mail contacts on GrapheneOS. Sign in to Proton, unlock keys on the device, and the app writes contacts into Android’s system Contacts provider. The stock dialer and contacts app see them like any other native contact. No Google account and no Play Services.

Question 2

Is Proton contact sync two-way (push and pull)?

Accepted Answer

Yes. Pull brings Proton contacts onto the phone. Push writes local creates, edits, and deletes back to Proton as encrypted contacts. Change a number in the native contacts app and it can go back to Proton. Change it in Proton Mail and the next sync brings it down.

Question 3

What happens if I wipe GrapheneOS or lose the phone?

Accepted Answer

The durable copy is Proton, not the handset. If the phone is lost, stolen, or wiped, the contacts are still in the Proton account. Set up GrapheneOS again, sign in to AlpenSync, and pull the book back into the stock contacts app. That is the point of two-way sync on a de-Googled phone: native contacts without depending on the device to survive.

Question 4

Does this need Google Play Services or a Google account?

Accepted Answer

No. AlpenSync is built for GrapheneOS and similar de-Googled Android (including LineageOS). It uses Android’s built-in sync framework and WorkManager. There is no Firebase, no FCM, and no Google backup of the address book.

Question 5

Where do contacts live, and is cryptography on-device?

Accepted Answer

Proton stores contacts as encrypted vCards. AlpenSync decrypts them on the device and writes the result into Android’s Contacts provider so the dialer can use them. That means contacts are decrypted on the phone while they are in the system provider, the same exposure as any contacts sync app. Cryptography stays on-device; the app is a client, never a relay.

Question 6

Is AlpenSync affiliated with Proton or GrapheneOS? Is it finished?

Accepted Answer

AlpenSync is an independent GPL-3.0 project. It is not affiliated with, endorsed by, or supported by Proton AG or the GrapheneOS project. It uses Proton’s undocumented, unofficial API, so sync may break when Proton changes something. The project is in development; the source is the product.

AlpenSync Terms of Use

1. License

2. Not Proton, not GrapheneOS

3. Unofficial API

4. No warranty

5. Limitation of liability

6. What you must not rely on AlpenSync for

7. Your responsibilities

8. Privacy

9. Contributions

10. Changes

11. Contact