WORK-011 - Device Key (Phase A + B + D)

Feature: FEAT-006-device-key.md Status: Complete

Tasks

1. Create DeviceKeyService
- Files: lib/services/device_key_service.dart
- Generates/loads key from FlutterSecureStorage
- Exposes devicePubkeyProvider (StateProvider)
2. Register device signer at boot
- Files: lib/main.dart
- In storageReadyProvider, after SQLite init
- signIn(setAsActive: false), sets devicePubkeyProvider
3. Device key UI in profile screen
- Files: lib/screens/profile_screen.dart
- Shows truncated npub, copy private key with warning dialog
4. Rewrite bookmarks to use device key
- Files: lib/services/bookmarks_service.dart, lib/widgets/app_detail_widgets.dart, lib/widgets/floating_overflow_menu.dart
- Changed from FutureProvider to synchronous Provider
- No manual nip44Decrypt calls (EncryptableModel auto-decrypts)
- No sign-in gate; always available
5. Rewrite unmanaged apps to use device key
- Files: lib/services/unmanaged_apps_service.dart, lib/services/updates_service.dart
- Changed from FutureProvider to synchronous Provider
- No sign-in gate
6. Remove sign-in gate from SaveAppDialog
- Files: lib/widgets/bookmark_widgets.dart
- Removed SignInPrompt, uses device signer directly
7. Remove appStackEventFilter, use #h tag filtering
- Files: lib/constants/app_constants.dart, lib/screens/user_screen.dart, lib/widgets/app_stack_container.dart, lib/widgets/bookmark_widgets.dart
- Removed filter function entirely
- Public stack queries now use '#h': {kZapstoreCommunityPubkey} tag
8. Migrate Amber private stacks on sign-in
- Files: lib/services/device_backup_service.dart, lib/services/device_key_service.dart
- Offers restore before migration so the final device key is chosen first
- Queries Amber-authored encrypted AppStacks after Amber connection
- Merges them into device-authored encrypted stacks using the device signer
- Normalizes legacy installed/unmanaged d-tags to current identifiers
- Rechecks idempotently on every sign-in; failed decrypts remain retryable
9. Store device key backups in encrypted settings
- Files: lib/services/device_backup_service.dart
- Uses device-signed CustomData with d=zapstore-settings
- Stores NIP-44 Amber recovery capsules authorized by Amber signatures
- Ignores legacy Amber-signed settings
10. Self-review against INVARIANTS.md
11. Centralize private 30267/30078 signing
- Device signer only, encrypted-stack h-tag rejection, 16-bit NIP-13
- Purplebase worker executor keeps mining off Flutter's main isolate
12. Add boot-only private event synchronization
- One cancellable stream=false request for device-authored 30267/30078
- Private consumers use LocalSource only
13. Replace Amber-owned settings backup
- Device-signed zapstore-settings with Amber recovery capsules and p tags
- Ignore all legacy Amber-signed settings
14. Repair Amber migration
- Explicitly decrypt Amber stacks before merge
- Cover bookmarks, installed, unmanaged, and arbitrary encrypted stacks
- Recheck idempotently on every Amber sign-in
15. Move trusted-signers CustomData to device ownership
16. Consolidate bookmark writes and private stack reads
17. Add lifecycle, failure, migration, and PoW tests

Test Coverage

Scenario	Expected	Status
Device private write	Device author, valid PoW, local save	[x]
Invalid private policy	Unknown 30078 and encrypted h-tag rejected	[x]
PoW cancellation	Worker terminates and tags remain unchanged	[x]
Boot sync lifecycle	Single-flight and cancellable	[x]
Bookmark write overlap	Serialized monotonic replacements	[x]
Bookmark save failure	Optimistic state rolls back	[x]
Amber bookmark migration	Imperative result explicitly decrypts	[x]
Recovery injection	Amber authorization required	[x]
Recovery cancellation	No work restarts after cancellation	[x]
Full verification	App, models, and Purplebase suites pass	[x]

Decisions

2026-05-07 - Migrate Amber-authored private stacks

Context: Users may have bookmarks encrypted to their Amber key. Decision: On Amber connection, migrate encrypted AppStacks authored by the Amber pubkey to equivalent device-key stacks. Rationale: Private data should follow the new device-key ownership model without losing existing saved apps, installed-app backups, or unmanaged app state.

2026-05-07 - Synchronous providers for bookmarks/unmanaged apps

Context: Previously FutureProvider because of manual decrypt. Now EncryptableModel auto-decrypts. Decision: Changed to synchronous Provider<Set>. Rationale: EncryptableModel.prepareAfterLoading runs in RequestNotifier before emission. By the time the provider reads the stack, privateAppIds is already decrypted.

2026-05-07 - #h tag replaces schemaFilter

Context: appStackEventFilter rejected encrypted stacks and stacks without app refs. Decision: Removed entirely. Public stacks are identified by having '#h': {communityPubkey} tag. Rationale: Per invariant "Encrypted stacks MUST NOT include a community h tag", filtering by #h naturally excludes all private stacks.

2026-05-07 - Device backups live inside settings

Status: Superseded by the 2026-07-13 device-settings decision below. Context: Device key backup needs to be tied to the user's encrypted settings event, not a separate replaceable event. Decision: Store backup entries inside the Amber-signed CustomData event with d=zapstore-settings, under the deviceBackups JSON key. Rationale: Keeps backup state with settings and avoids a standalone zapstore-device-backup event. The entire settings JSON object is NIP-44 encrypted before signing.

2026-07-13 - All private events are device-owned

Context: Amber ownership made private state depend on the current identity and allowed private write paths to drift. Decision: Every private kind 30267/30078 event is device-signed. Public 30267 stacks remain Amber-signed and carry the community h tag. Rationale: The device key is always available and is the stable owner of per-device state.

2026-07-13 - Device settings contain recovery capsules

Context: Amber must recover a device nsec without authoring the settings event or owning device settings. Decision: zapstore-settings is signed by the device key. Its versioned envelope stores device-private data plus NIP-44 capsules addressed to Amber keys and indexed by p tags. Capsules include an embedded Amber-signed authorization binding the Amber identity to the device pubkey. Rationale: Settings remain per-device while Amber remains an orthogonal recovery recipient, while copied or attacker-created capsules cannot inject a device key that Amber never authorized.

2026-07-13 - Boot-only relay ingestion

Context: Private state changes originate on the device and live subscriptions waste relay and lifecycle resources. Decision: Fetch device-authored private events once at boot with stream:false; UI providers are local-only. Amber recovery/migration is the only sign-in-time one-shot exception. Rationale: Preserves local-first rendering and avoids duplicate or leaked subscriptions.

2026-07-13 - 16-bit off-isolate proof of work

Context: Private events need NIP-13 without running CPU-bound mining on Flutter's main isolate. Decision: Apply 16-bit PoW through a cancellable Purplebase worker executor. Rationale: 16 bits is a practical mobile spam cost; worker execution keeps rendering responsive.

Spec Issues

None

Progress Notes

2026-05-07: Phase A, B, and D complete. Migration added for Amber-authored private stacks. Analysis could not be rerun in this sandbox because fvm and pub-cache reads are blocked.

2026-05-07: Restore ordering hardened: if an Amber backup contains other device keys, the restore/keep-current choice happens before migration and backup. Migration completion is keyed by both Amber pubkey and final device pubkey, and empty migration results are left retryable.

2026-05-07: Device key backup moved into the encrypted zapstore-settings CustomData event. No zapstore-device-backup event is written.

2026-07-13: FEAT-006 was updated by explicit product authorization. The new contract supersedes the earlier Amber-signed settings decision and ignores legacy Amber settings even when that loses old backups.

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