password_manager/AGENTS.md

Password Vault — Agent Context

Project Overview

An offline-first, single-file password manager built with Svelte 5 (runes-based reactivity). All data is encrypted in-browser with AES-256-GCM and stored in IndexedDB. The production build is a single dist/index.html with zero network dependencies — it works from file://, USB, or any static server.

Architecture

src/
├── App.svelte                  # Root component — routes between LockScreen, MainLayout
├── main.js                     # Entry point
├── components/
│   ├── LockScreen.svelte       # Master password setup + unlock UI
│   ├── MainLayout.svelte       # Shell: sidebar + content area
│   ├── Sidebar.svelte          # Group list + search bar
│   ├── EntryList.svelte        # Credential entries grid
│   ├── EntryForm.svelte        # Create/edit credential form
│   ├── EntryDetail.svelte      # View single entry (copy password/username)
│   ├── ImportExport.svelte     # JSON import/export with merge/replace
│   └── SettingsDialog.svelte   # Auto-lock and tab-switch settings
├── lib/
│   ├── crypto/crypto.js        # Web Crypto API: PBKDF2 key derivation, AES-GCM encrypt/decrypt, password generator
│   ├── storage/db.js           # IndexedDB layer (idb wrapper): entries, groups, meta stores, exportSelected(groupIds)
│   ├── models/schema.js        # Data models: CredentialEntry, Group; validation; ID generation
│   ├── autofocus.js            # Svelte action for autofocus on mount
│   └── stores/
│       ├── app.svelte.js       # AppStore: $state(isUnlocked, encryptionKey, salt)
│       ├── security.svelte.js  # Auto-lock timer, visibility change, beforeunload cleanup
│       ├── search.svelte.js    # Reactive search state
│       └── settings.svelte.js  # Reactive settings (auto-lock minutes, tab-switch lock)

Key Design Decisions

• Svelte 5 runes — Use $state, $derived, $effect. Props-based event passing (no Svelte events). Event handler attributes are all lower-case (e.g. oninput)
• No external crypto libraries — Uses the browser's native Web Crypto API exclusively.
• Key never persisted — Encryption key lives only in $state memory; cleared on lock, tab switch, or page close.
• Single-file build — vite-plugin-singlefile inlines all JS/CSS; post-build script inlines favicon.
• IndexedDB via idb — Three stores: entries, groups, meta. Only encryptedPassword is encrypted at rest; titles, usernames, URLs, and notes are plaintext for searchability.
• PBKDF2 key derivation — 600,000 iterations, SHA-256, 256-bit AES-GCM key.
• GROUP_COLORS exported from schema.js — Shared between createGroup() and Sidebar.svelte.

Encryption Flow

Master Password → PBKDF2 (600k iters, 16-byte salt) → AES-256-GCM Key → encrypt/decrypt credentials

Password verification uses a test payload (random string encrypted at vault creation). On unlock, the entered password derives a key that must successfully decrypt the test payload.

Scripts

Command	Description
npm run dev	Vite dev server with HMR on :5173
npm run build	Production build → dist/index.html (single self-contained file)
npm run preview	Preview production build
npm run test	Vitest (watch mode)
npm run test:run	Vitest (single run)

Testing

• Framework: Vitest with jsdom environment
• Test setup: tests/setup.js (fake-indexeddb polyfill, Web Crypto API polyfill)
• Test files:
  • tests/lib/crypto/crypto.test.js — Password generation, key derivation, encrypt/decrypt, verify, test payload, base64 utils
  • tests/lib/models/schema.test.js — ID generation, entry/group CRUD, validation, trash group
  • tests/lib/storage/db.test.js — Vault meta, settings, groups CRUD, entries CRUD, search, trash, export/import
  • tests/lib/stores/app.test.js — AppStore state and lockVault
  • tests/lib/stores/search.test.js — SearchStore query, group filter, clear
  • tests/lib/stores/settings.test.js — SettingsStore defaults, load, save
  • tests/lib/stores/security.test.js — Auto-lock timer, visibility change, beforeunload, activity reset
• Run with npm run test or npm run test:run

Security Notes

• Only encryptedPassword is encrypted at rest; other fields (title, username, URL, notes) are plaintext in IndexedDB.
• testPlaintext for password verification is stored unencrypted in the meta store.
• Auto-lock triggers on tab visibility change and configurable inactivity timer (default 5 min).
• Clipboard auto-clears after 15 seconds.
• No browser fingerprinting or anti-keylogger protections.

Export / Import

• exportSelected(groupIds, options) — group IDs to export; null/[] = full export (include '' for ungrouped). options = { vaultKey, password = '', useExistingPassword = false }. An explicit protection choice is required; every protected export AES-256-GCM-seals the whole payload (titles/usernames/notes included) into { format: 'encrypted-export', salt, data }.
  • New password (options.password): re-keys every exported entry's password to a key derived from that password + a fresh random salt (embedded in the envelope), so import needs only this password — never the vault's.
  • Reuse existing password (options.useExistingPassword): seals with the vault's own key and keeps the vault's salt embedded, so import derives the key from the vault master password. No second password to create/remember.
  • No option set: falls back to a plaintext JSON export (entries keep source-vault-encrypted passwords) for backward compatibility; the UI never offers this.
• importAll(data, mode, password, targetKey) detects a sealed export (data.format === 'encrypted-export'): password is whichever password opens the envelope — a separate export password OR the source vault's master password (for reuse-existing). A wrong password rejects the import (never silently skips). The entry loop decrypts with the reproduced source key and re-encrypts under targetKey.
• ImportExport.svelte fetches groups/entries on modal open and shows a checkbox list for group selection with live entry count. The export dialog forces an explicit choice via two radio options: "Use a new password" (shows a short password field, validated non-empty) or "Reuse my vault password". The import dialog's single password field is generic (export password for sealed files, source vault master for plain/old files).

Known Bug Fixes

• base64ToUint8Array was used in db.js importAll() but never imported — now imported from crypto.js.
• handlePermanentDelete() in EntryDetail.svelte called moveToTrash() + emptyTrash() (wiping ALL trash) — now uses deleteEntry() directly.