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* Make peer registry and local announce state lock-backed The main actor answered isPeerConnected/peerNickname/currentPeerSnapshots and flipped runtime capability bits by blocking on collectionsQueue behind whatever transport work was in flight. Peer state now lives in a lock-backed BLEPeerRegistryStore (every registry mutation is a single whole-transition method, so readers never observe a torn state), and the runtime capability bits move into BLELocalIdentityStateStore next to the identity they ride announces with. No transport entry point called from the main actor blocks on a transport queue for peer state anymore. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Move BLE link egress/ingress buffers to bleQueue ownership pendingPeripheralWrites, pendingNotifications, and pendingWriteBuffers were collectionsQueue-guarded, but every producer and drain already runs on bleQueue next to the CoreBluetooth objects they feed — each access paid a cross-queue barrier for state that never leaves the radio thread, and the notification drain even invoked peripheralManager.updateValue from the collections queue. They are now bleQueue-confined like the link state store: CB delegate callbacks and drains touch them directly, and the few engine-side entry points hop to bleQueue (the direction the transport's sync-edge order already allows). This clears most bleQueue-to-collectionsQueue sync edges ahead of merging the collections queue into the message queue. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Stop bleQueue maintenance and status paths from blocking on collectionsQueue The traffic-burst tracker becomes a lock-backed monitor (written by the receive pipeline, read by scan-duty adaptation and announce pacing on bleQueue), the status-log peer summary and topology refresh read the already lock-backed registry directly, and the stalled-fragment reap moves to an async collections hop with the gossip resync request inside it. bleQueue no longer sync-waits on the collections queue anywhere. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Unify the message and collections queues into one serial engine queue The old model ran a concurrent message queue over a second concurrent collections queue whose barrier flags served as the real mutual exclusion — every field carried an ownership comment, and correctness lived in per-site discipline. The message queue is now a single serial engine queue that owns all mesh protocol state; the collections queue, its 98 sync/async hops, and every barrier flag are gone. Cross-thread callers go through onEngine, which documents and (in debug) enforces the transport's sync-edge order: main and test threads may block on the engine, the engine may block on bleQueue and the crypto/identity queues, and nothing may block the other way. The debug trap caught two latent inversions the leaf-lock structure had been masking: the verified-announce rebind path re-resolved the ingress link through the engine from inside its bleQueue critical section (it now receives the already-resolved link), and the noise session-generation closures sync-re-entered the engine from the noise manager's queue while their own engine slot was blocked on it (they now touch engine state directly, which the held slot makes exclusive). BLE throughput is orders of magnitude below what one serial queue sustains; the full suite runs at identical speed. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Wire gateway/bridge/panic features to capability ports, not BLEService App wiring discovered mesh-only features by casting the Transport to the concrete BLEService class in nine places. Those surfaces are now three capability protocols — BluetoothStateReporting, PanicResettingTransport, and MeshBridgingTransport — discovered with as? like any optional capability, so the bootstrapper, panic flow, and lifecycle coordinator no longer name the concrete transport at all. A future second mesh transport picks up gateway/bridge wiring and the panic lifecycle by conforming, and the remaining Transport god-protocol requirements can migrate to the same pattern. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Extract mesh-ping diagnostics state into a pure engine-confined tracker First slice of the feature-module direction: BLEMeshPingTracker owns the outstanding-probe map and the per-link inbound response budget as pure state (register/resolve/expire/reset), so the security invariants — a pong only resolves against the probed peer, the budget keys on the ingress link because claimed senders are forgeable, panic reset drops probes and budget together — are now unit-tested without queues or radios. The transport keeps only packet I/O, timers, and main-actor delivery around it. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Document the V3 transport architecture and remaining roadmap Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Resolve the pass-6 review findings and the proof-timeout drain defect Periphery: the registry store's unused forwarders are gone (the struct method stays — it has direct tests). F1: refreshPeerIdentity, deliverBridgedEnvelope, and the three panic fences route through onEngine, so every sync entry onto the engine now carries the bleQueue trap. F2: the registry-store ownership comments state the real writer set (engine plus the two bleQueue link-drop paths). F7: BLEQueueContractTests pins the contract — only onEngine may sync-enter the engine, transport code never sync-dispatches to main, and the collections queue stays deleted — with a queue-contract-ok waiver for the two sanctioned lines. The real defect behind the timeoutRestoredSession CI flake: a timeout-restore parks the outbound queues until the convergence retry, but the capability-proof watchdog armed at the original authentication kept draining them when it fired — encrypting the parked traffic under restored keys the counterpart may have discarded, the exact silent loss the defer path exists to prevent. Deferred peers are now tracked and the watchdog drain respects the same rule; the test fires the watchdog deterministically inside the deferred window instead of losing that race only on stalled runners. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Extract private-media session state into a lock-backed store The six generation-keyed maps plus the convergence-deferral set move out of BLEService into BLEPrivateMediaSessionStore, each transition one whole method under a leaf lock with direct unit tests (generation rotation rejects mismatched waiters, stale proofs cannot classify a replacement session, expiry requires the live deadline identity, clears rebase waiters onto a nil-generation deadline, peer-state sends are once per generation per kind). Being a leaf lock also simplifies two contracts: the send policy is now answered entirely from locks (the main actor no longer sync-enters the engine for it), and the noise-manager critical sections call ordinary store methods instead of relying on the held-engine-slot direct-access subtlety. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Split the mesh-only Transport surface into capability protocols Transport kept ~50 requirements that only the BLE mesh implements — files/private media, voice, courier, groups, board, diagnostics, verification, archive — held together by an extension of inert defaults, so every call site compiled against a surface most transports faked. Those are now eight capability protocols (MeshFileTransferring, MeshVoiceStreaming, MeshCourierTransporting, MeshGroupMessaging, MeshBoardBroadcasting, MeshDiagnosing, MeshVerifying, MeshPublicArchiving) discovered with as?, joining the bridging/panic ports from the previous pass. Consumers resolve the capability they need; where the old defaults encoded a safe floor the caller keeps it explicitly (private-media policy degrades to blockedDowngrade). The inert-defaults extension is deleted, along with the never-implemented acceptPendingFile/declinePendingFile pair. NostrTransport is untouched — it only ever implemented the core. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Update the V3 doc for the completed feature-peeling and Transport split Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Drop the dead three-argument sendFilePrivate overload Every production caller goes through the allowLegacyFallback variant; the short form only existed as a Transport-era forwarding default. Tests that used it on the concrete service now state the fallback decision explicitly, which is the point of the parameter. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Decide the link-auth boundary: bindings become engine-owned The atomicity that keeps link-auth on bleQueue exists to stop a binding from changing between a security check and its action; once every rebind is an engine operation, the engine's serial slot gives the same guarantee, the stolen-link residual is unchanged (directed payloads are Noise ciphertext), and the receive path lands in its sans-I/O shape — the link layer reports bytes-plus-linkID and the engine resolves the sender. Records the extraction order too: the binding-free radio half first (after #1521 lands — it collides in the scanPlan region), then bindings, then the delegates behind the port. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Fix two bleQueue-to-engine sync edges the queue merge created The collections-to-engine conversion turned two formerly leaf-lock sync calls into onEngine calls reachable from bleQueue, where the debug trap (correctly) aborts: flushDirectedSpool runs from bleQueue maintenance and now hops to the engine asynchronously, and ingress recording — which must answer the duplicate gate on bleQueue the moment a frame decodes — moves to a lock-backed BLEIngressLinkStore read by the engine's relay and routing decisions. Unit suites never hit either path (no CoreBluetooth managers means no maintenance timer and no live receive path); the iOS simulator job boots the real app as its test host, which is exactly where the maintenance trap fired. The ingress one would have trapped a real device on its first received packet — worth a device pass before release. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Route all deferred engine work through an injectable scheduler Relay jitter, announce delays, the ping and capability-proof deadlines, notification retry backoff, and fragment pacing all reached the engine through raw messageQueue.asyncAfter with product constants as deadlines — the hidden-elapsed-deadline flake class that the test-timing hygiene rules exist to contain, testable only by racing the wall clock. BLEEngineScheduling is now the transport's single source of engine delay: production is a thin veneer over the engine queue, tests inject a manually advanced clock whose advance() returns only after the released work has finished on the engine. The queue-contract test pins the seam (no raw messageQueue.asyncAfter), and the ping deadline gets the pattern's proof: the real 10s constant asserted in milliseconds — must not fire early, fires exactly once at the deadline, stays consumed after. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Assert the armed deadline count in the injected-clock ping test 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.
Getting a copy you can trust
Install from the App Store, or build from source you have verified. A compiled build from anywhere else cannot be verified — see Verifying bitchat for how to check source against the per-release hash manifest, and for what to do if that is the only build you can get.
This matters more than it usually would: this repository has been the target of takedown demands, and when a repository or releases page disappears, mirrors appear that nobody can check.
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 servers. Note that the mesh does use a persistent per-device identifier derived from your identity key — see the whitepaper on identity and metadata for what a nearby radio can observe
- Private Message End-to-End Encryption: Noise Protocol for mesh, BitChat private envelopes for Nostr fallback
- 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 for live sessions (store-and-forward mail is sealed without it — see the whitepaper)
- 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
- BitChat Private Envelopes: App-specific encrypted private messages over Nostr relays
- Ephemeral Keys: Fresh cryptographic identity per geohash area
BitChat's private-envelope format is proprietary and is not NIP-17,
NIP-44, or NIP-59 compatible. It uses Nostr as a relay transport but only
interoperates with BitChat clients: private payloads travel inside kind-1059
events whose v2:-prefixed content is a BitChat-specific XChaCha20-Poly1305
construction, not NIP-44 encryption.
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
- BitChat's app-specific private-envelope encryption
- 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
open bitchat.xcodeproj
For a signed device build, create your ignored local configuration and replace the example team ID with your Apple Developer Team ID:
cp Configs/Local.xcconfig.example Configs/Local.xcconfig
Local.xcconfig.example derives unique app and App Group identifiers from that
team ID. The entitlement files already reference $(APP_GROUP_ID), so tracked
project or entitlement files do not need to be edited.
Useful command-line checks from the repository root:
# macOS Debug build without signing
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (macOS)" \
-configuration Debug CODE_SIGNING_ALLOWED=NO build
# Full SwiftPM test suite
swift test
# iOS simulator tests
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (iOS)" \
-sdk iphonesimulator \
-destination 'platform=iOS Simulator,name=iPhone 17' test
If iPhone 17 is unavailable, choose an installed simulator from:
xcodebuild -showdestinations -project bitchat.xcodeproj -scheme "bitchat (iOS)"
Option 2: Using just
brew install just
just check
just run
just build and just run use the current bitchat (macOS) scheme and keep
Xcode output in the ignored .DerivedData/ directory. They never patch source,
project, configuration, or entitlement files.
just clean removes only .DerivedData/ and .build/. It does not invoke Git
or restore tracked files, so uncommitted work is preserved. just test runs the
SwiftPM suite and just test-ios runs the iPhone 17 simulator suite.
Localization
- App localizations live in
bitchat/Localizable.xcstrings. - Share extension strings are separate in
bitchatShareExtension/Localization/Localizable.xcstrings. - 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.