TL;DR: fully offline, AES-256-GCM everywhere, Argon2id key derivation, secrets decrypted only in the Rust core, memory wiped on lock, no telemetry, minimal dependencies.

┌─ WebView (TypeScript) ───────────┐      ┌─ Rust core ─────────────────┐
│ lists, search, modals, themes    │ IPC  │ vault, crypto, OTP engine,  │
│ receives: codes + metadata only  │◄────►│ importers, keychain, lock   │
│ sends: user intent (no secrets)  │      │ state (locked = wiped RAM)  │
└──────────────────────────────────┘      └─────────────────────────────┘

• Raw account secrets never cross the IPC boundary, except inside the reveal-secret dialog and exports — both gated by re-authentication.
• When the vault is locked, the decrypted state does not exist in memory at all: the lock screen is not a layer hiding data; the data is gone (DerefDrop → zeroize).

Master-password verification uses the AEAD tag of the stored vault (re-derive + decrypt attempt): constant oracles-free, and identical to what an attacker offline would have to do. Wrong password ⇒ generic error.

The keychain mode stores a random 256-bit vault key in the OS credential manager (Windows Credential Manager via keyring with windows-native). It protects the vault file against theft, but not against an attacker seated at an unlocked session — the master-password mode is the recommendation for high-value secrets.

• Zeroizing containers for the master key, derived keys, and per-account secret bytes.
• Session + pending-import drafts are dropped (zeroized) on: manual lock, auto-lock, minimize-lock, and window close.
• Screen-capture protection: set_content_protected(true) — screenshots and screen-share see a black window (Windows).
• No secrets/codes are ever logged; there is no persistent logging at all in v1.

• Strict CSP: default-src 'self' (+ ipc: for Tauri) — no remote content, ever.
• No HTTP client in the Rust binary; nothing in the app performs network I/O.
• Capability model: only core:default and dialog:default are granted.
• Settings file contains no secrets (theme/density/geometry only); vault and settings writes are atomic (temp → replace, .bak of last good copy).

• ✅ Vault file theft (password mode), casual snooping (keychain mode), shoulder surfing (hidden codes + capture protection), tampered backups (AEAD), corrupt imports (validation + explicit confirmation), accidental wipe (atomic writes + .bak).
• ⚠️ Not defended: a fully compromised OS (malware reading the unlocked process memory or the OS credential store), physical DMA attacks, weak master passwords. These are out of scope for a desktop TOTP app.

Open a private security advisory on GitHub rather than a public issue.