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* Friend-courier store-and-forward: mutual favorites carry sealed messages to offline peers When a private message has no reachable transport, the router now seals it to the recipient's Noise static key (new one-way Noise X pattern) and hands the envelope to up to three connected mutual favorites. Couriers store the opaque ciphertext under strict quotas (20 total, 5 per depositor, 16 KiB, 24 h) and hand it over when the recipient's announce matches a rotating HMAC recipient tag; the recipient opens it and the message flows through the normal private-message pipeline, so dedup and delivery acks just work. - CourierEnvelope TLV + courierEnvelope (0x04) message type in BitFoundation - Noise X one-way pattern reusing the existing handshake machinery, domain-separated by a courier prologue; sender identity authenticated via the ss DH (no forward secrecy - documented tradeoff) - CourierStore with eviction, file persistence, and panic-wipe integration - Rotating recipient tags (HMAC over epoch day) so carried envelopes don't correlate for observers who don't already know the recipient's key - New "carried" delivery status with figure.walk glyph; header indicator while carrying mail for others - Three-node end-to-end test ferrying packets through real BLEService instances, plus codec/crypto/store/router suites (986 tests green) Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Fix courier handoff verification and directed sends * Authenticate courier deposits by ingress peer * Gate courier handover on direct announces and isolate store test Envelopes are removed from the courier store optimistically, so releasing them on a relayed (multi-hop) announce risks losing carried mail to a speculative flood that never reaches the recipient. Handover now also requires the announce to have arrived directly (full TTL), i.e. an actual encounter with a live link; regression test builds a relayed copy of a genuinely signed announce (TTL is excluded from announce signatures). Also make CourierStore's on-disk location injectable so the persistence test round-trips through a temp directory instead of wiping the real Application Support store, and reattach BLEAnnounceHandler's doc comment to the class it describes. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Use Xcode-bundled Swift in CI instead of a standalone toolchain The unpinned setup-swift action installs Swift 6.1, which refuses the SDK on runner images that have rolled to Xcode 26.5 ("this SDK is not supported by the compiler"). Jobs passed or failed depending on which image they landed on. The Xcode-bundled toolchain always matches the image's SDK, and matches local development. Cache keys now include the toolchain version so artifacts from one compiler are never restored into builds with another. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Drop couriered mail from blocked senders at envelope open The UI-layer block check (isPeerBlocked in the transport event coordinator) resolves a fingerprint from the live session or peer list, but a couriered message arrives precisely when its sender is absent — no session, no registry entry — so the check failed open and a blocked identity's mail was delivered anyway. Gate in openCourierEnvelope, where the sealed sender's full static key is in hand. End-to-end test ferries a full deposit→carry→handover round and verifies the envelope from a blocked sender never reaches the delegate (confirmed failing without the gate). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Fix favorites end-to-end: peer-list dedup, Nostr sync, /fav key corruption - UnifiedPeerService: dedup offline favorites against mesh peers by noise key. Phase 2 compared a 64-hex noise-key PeerID against 16-hex mesh IDs (never equal), leaving only a nickname+isConnected heuristic — a mutual favorite that was reachable-but-not-connected or renamed rendered twice, and a same-nick stranger could suppress a favorite entirely. - Nostr inbound: intercept [FAVORITED]/[UNFAVORITED] markers in the live PM handler so they update theyFavoritedUs instead of rendering as chat text; mutual favorites can now form over Nostr. Delete the dead favorite-aware PM variant and ChatNostrCoordinator.handleFavoriteNotification (unwired, parsed a stale FAVORITE:TRUE|… format no sender emits). - NostrTransport.isPeerReachable: match short form regardless of incoming ID width — toggling an offline favorite (addressed by 64-hex noise key) was silently dropped with no reachable transport. - BLEService.sendPrivateMessage: normalize recipient to the short ID like sendFilePrivate, so a 64-hex target hits the existing Noise session instead of initiating a handshake with a 32-byte wire recipient ID. - /fav, /unfav: stop writing Data(hexString: peerID.id) — the 8-byte routing ID for mesh peers — into the favorites store as a "noise key", and stop double-sending the favorite notification; delegate to toggleFavorite with a proper state check. - FavoritesPersistenceService.updatePeerFavoritedUs: keep the stored nickname when the caller passes the "Unknown" placeholder. - Bump marketing version to 1.5.4. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Route DMs to mutual favorites via Nostr when a mesh-keyed peer goes offline Field-tested on device: with a DM window opened while the peer was on mesh (conversation keyed by the short 16-hex ID), walking out of range and sending failed instantly with "peer not reachable" even though the header showed the peer as Nostr-reachable (mutual favorite, npub known). sendPrivateMessage derived the favorites key as Data(hexString: peerID.id) — for a short mesh ID that is the 8-byte routing ID, never the noise key — so the mutual-favorite/Nostr-key checks always came up empty and the send failed before reaching MessageRouter. Conversations keyed by the full 64-hex noise-key ID (opened from the offline favorite row) were unaffected, which is why later tests appeared to work. Resolve the noise key properly (peerID.noiseKey, then the unified peer row, then the favorites store by derived short ID) and add a regression test for the mesh-keyed-peer-goes-offline case. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Label Nostr DMs from favorites with their stored nickname Field-tested: a DM delivered over the Nostr fallback rendered as "anon#678e" instead of the sender's name. The inbound handler named the sender via displayNameForNostrPubkey, which only knows geohash-scoped names — even though the pipeline had already resolved the sender's noise key (the conversation is keyed by it). When the conversation key carries a noise key, prefer the favorite's stored nickname; geohash DMs (nostr_ keys) keep the anon geo name. This also stops an inbound Nostr [FAVORITED] from overwriting the stored nickname with the anon fallback, since the same name feeds updatePeerFavoritedUs. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Fix courier path for offline favorites addressed by noise-key IDs Two Codex review findings, both the same ID-width confusion this PR targets, in the courier flow: - CourierDirectory.favoritesBacked resolved recipients only via getFavoriteStatus(forPeerID:), which requires a short 16-hex ID — offline favorites are addressed by the full 64-hex noise-key ID, so attemptCourierDeposit silently bailed for exactly the peers couriers exist to serve. The 64-hex ID now yields its own key directly. - openCourierEnvelope emitted the derived short mesh ID even when the sender has no live mesh identity, landing couriered mail in an unresolvable short-ID thread labeled "Unknown". Absent senders now emit the full noise-key ID so the message joins the stable favorite conversation; present senders keep the live short-ID thread. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> --------- Co-authored-by: jack <jackjackbits@users.noreply.github.com> Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
bitchat
A decentralized peer-to-peer messaging app with dual transport architecture: local Bluetooth mesh networks for offline communication and internet-based Nostr protocol for global reach. No accounts, no phone numbers, no central servers. It's the side-groupchat.
License
This project is released into the public domain. See the LICENSE file for details.
Features
- Dual Transport Architecture: Bluetooth mesh for offline + Nostr protocol for internet-based messaging
- Location-Based Channels: Geographic chat rooms using geohash coordinates over global Nostr relays
- Intelligent Message Routing: Automatically chooses best transport (Bluetooth → Nostr fallback)
- Decentralized Mesh Network: Automatic peer discovery and multi-hop message relay over Bluetooth LE
- Privacy First: No accounts, no phone numbers, no persistent identifiers
- Private Message End-to-End Encryption: Noise Protocol for mesh, NIP-17 for Nostr
- IRC-Style Commands: Familiar
/slap,/msg,/whostyle interface - Universal App: Native support for iOS and macOS
- Emergency Wipe: Triple-tap to instantly clear all data
- Performance Optimizations: LZ4 message compression, adaptive battery modes, and optimized networking
Technical Architecture
BitChat uses a hybrid messaging architecture with two complementary transport layers:
Bluetooth Mesh Network (Offline)
- Local Communication: Direct peer-to-peer within Bluetooth range
- Multi-hop Relay: Messages route through nearby devices (max 7 hops)
- No Internet Required: Works completely offline in disaster scenarios
- Noise Protocol Encryption: End-to-end encryption with forward secrecy
- Binary Protocol: Compact packet format optimized for Bluetooth LE constraints
- Automatic Discovery: Peer discovery and connection management
- Adaptive Power: Battery-optimized duty cycling
Nostr Protocol (Internet)
- Global Reach: Connect with users worldwide via internet relays
- Location Channels: Geographic chat rooms using geohash coordinates
- 290+ Relay Network: Distributed across the globe for reliability
- NIP-17 Encryption: Gift-wrapped private messages for internet privacy
- Ephemeral Keys: Fresh cryptographic identity per geohash area
Channel Types
mesh #bluetooth
- Transport: Bluetooth Low Energy mesh network
- Scope: Local devices within multi-hop range
- Internet: Not required
- Use Case: Offline communication, protests, disasters, remote areas
Location Channels (block #dr5rsj7, neighborhood #dr5rs, country #dr)
- Transport: Nostr protocol over internet
- Scope: Geographic areas defined by geohash precision
block(7 chars): City block levelneighborhood(6 chars): District/neighborhoodcity(5 chars): City levelprovince(4 chars): State/provinceregion(2 chars): Country/large region
- Internet: Required (connects to Nostr relays)
- Use Case: Location-based community chat, local events, regional discussions
Direct Message Routing
Private messages use intelligent transport selection:
-
Bluetooth First (preferred when available)
- Direct connection with established Noise session
- Fastest and most private option
-
Nostr Fallback (when Bluetooth unavailable)
- Uses recipient's Nostr public key
- NIP-17 gift-wrapping for privacy
- Routes through global relay network
-
Smart Queuing (when neither available)
- Messages queued until transport becomes available
- Automatic delivery when connection established
For detailed protocol documentation, see the Technical Whitepaper.
Setup
Option 1: Using Xcode
cd bitchat
open bitchat.xcodeproj
To run on a device there're a few steps to prepare the code:
- Clone the local configs:
cp Configs/Local.xcconfig.example Configs/Local.xcconfig - Add your Developer Team ID into the newly created
Configs/Local.xcconfig- Bundle ID would be set to
chat.bitchat.<team_id>(unless you set to something else)
- Bundle ID would be set to
- Entitlements need to be updated manually (TODO: Automate):
- Search and replace
group.chat.bitchatwithgroup.<your_bundle_id>(e.g.group.chat.bitchat.ABC123)
- Search and replace
Option 2: Using just
brew install just
Want to try this on macos: just run will set it up and run from source.
Run just clean afterwards to restore things to original state for mobile app building and development.
Localization
- Base app resources live under
bitchat/Localization/Base.lproj/. Add new copy toLocalizable.stringsand plural rules toLocalizable.stringsdict. - Share extension strings are separate in
bitchatShareExtension/Localization/Base.lproj/Localizable.strings. - Prefer keys that describe intent (
app_info.features.offline.title) and reuse existing ones where possible. - Run
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (macOS)" -configuration Debug CODE_SIGNING_ALLOWED=NO buildto compile-check any localization updates.