FreeFileSync Forum

Aha, that sounds logical. I'll stop pestering you then ;)

An official announcement has been made : https://proton.me/blog/drive-sdk-january-2026
The repo has had updates too, there's c# and kotlin code available.
However, there's no authentication yet. This release is meant for experimentation, not production.

It sounds like they are serious on unifying their codebase, makes a lot of sense wrt multiple platforms. If this SDK is that unified foundation, that's good news as well. It means that the public-facing SDK is not some project they must maintain separately.
But as you say, let's see it get shipped ...

Proton is putting together a javascript + C# SDK that they will be using as the cross-platform basis for their products going forward. This SDK will include support for Proton Drive.
I am hopeful that we might have Proton support in FreeFileSync in the future.

Here are some related blog posts ...