The short version:
- Secrets are encrypted at rest — OAuth tokens and credentials are stored with Fernet symmetric encryption; nothing secret is stored in plain text.
- The AI never sees your credentials. When Nell needs to act, she asks the application layer, which holds the tokens.
- Your content lives in an isolated, per-user vault — access outside it is a hard error, enforced in code.
- Transport is TLS, sessions are manageable per device, two-factor authentication is available, and login is lockout-protected.
The Security page describes everything in detail.