Security
Files are encrypted on your computer with a recovery key only you hold. Backup cannot recover the key.
The wrap is post-quantum: ML-KEM-768 together with X25519. File keys are wrapped to those public keys. The recovery key never leaves your computer.
Backups can't be deleted for 90 days. In that time nothing can be overwritten or deleted, not even by a compromised agent. New copies can still be added.
An agent can add backups. It cannot read or delete them. Neither can we.