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c7d551e2af
Replaces the when (onboardingState) in MainActivity and the ad-hoc back handling with a Navigation 3 back stack. Navigator, AppNavigator, the EntryProviderInstaller multibinding and the NavDisplay host live in :app for now; they move to a :core:navigation module once there is a second module to justify one. Onboarding is one destination, not eight. Its steps are driven by permission results and adapter state changes rather than by the user navigating, and going back a step has never been supported. Per-step routes would invent a history that does not exist, so the state machine stays and only the crossing into chat is a navigation event. That crossing uses resetTo, so Back cannot re-enter onboarding. Removes the OnBackPressedCallback that was constructed and registered inside a composable body, adding a callback on every recomposition of that branch. NavDisplay owns back now; it drives predictive back through androidx.navigationevent, and a second handler over the same gesture can detach the navigationevent input mid-gesture, so there must not be one. Chat still manages its overlays with booleans, so back consults ChatViewModel first through interceptBack. That parameter exists only until those overlays become routes. The back stack is seeded before setContent rather than from a LaunchedEffect: NavDisplay rejects an empty back stack and an effect does not run until after the first composition. Verified on a Pixel 9a: launch renders without the empty-backstack crash, chat is reached, Back exits to the launcher instead of re-entering onboarding, and relaunch is clean. Plus :app:assembleDebug and 591 unit tests. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MdKgoKZbL5K1wsn1WsES26
bitchat for Android
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.
This is the Android implementation of bitchat, fully protocol-compatible with the iOS version for cross-platform mesh communication.
See it in action
| Offline mesh conversation | Geohash globe picker |
|---|---|
 |
 |
License
This project is released into the public domain. See the LICENSE file for details.
Features
- Dual Transport Architecture: Bluetooth LE mesh for offline messaging, Nostr relays for internet-based messaging
- Location-Based Channels: Geographic chat rooms using geohash coordinates over Nostr relays
- Intelligent Message Routing: Automatically chooses the best transport, with queuing and retry when a peer is unreachable
- End-to-End Encryption: Noise Protocol (XX pattern, X25519 + ChaCha20-Poly1305) for private messages over the mesh
- Decentralized Mesh Network: Automatic peer discovery and multi-hop relay over Bluetooth LE (max 7 hops)
- Wi-Fi Aware Transport: Higher-bandwidth local mesh on supported devices
- Channel Chats: Topic-based group messaging with optional password protection (Argon2id + AES-256-GCM)
- IRC-Style Commands: Familiar
/join,/msg,/whostyle interface - Tor Support: Built-in Tor (Arti) for private internet connectivity
- Emergency Wipe: Triple-tap to instantly clear all data
- Cross-Platform: Binary protocol compatible with bitchat on iOS and macOS
Technical Architecture
Bluetooth Mesh Network (Offline)
- Direct peer-to-peer within Bluetooth range, multi-hop relay through nearby devices
- Noise Protocol sessions with forward secrecy; peer identities derived from static keys
- Compact binary packet format with fragmentation, TTL routing, and deduplication
- Adaptive duty cycling and connection limits for battery efficiency
- Foreground service keeps the mesh alive within Android background execution limits
Nostr Protocol (Internet)
- Global reach via public relays, geohash-based location channels
- Private messages fall back to Nostr for mutual favorites when the mesh is unavailable
- Ephemeral keys per geohash area
Android Stack
- Kotlin, Jetpack Compose (Material 3), MVVM
- Coroutines and Flow for all networking and state
- Core components:
MeshForegroundService(persistent connectivity),BluetoothMeshService/WifiAwareMeshService(transports),UnifiedMeshService(transport selection),NoiseSessionManager(encryption sessions),MessageRouter(mesh/Nostr routing with outbox retry)
Building
Requires Android Studio and the Android SDK (API 26+).
git clone https://github.com/permissionlesstech/bitchat-android.git
cd bitchat-android
./gradlew assembleDebug
Install on a connected device:
adb install -r app/build/outputs/apk/debug/app-debug.apk
The app requests Bluetooth, location (required for BLE scanning), and notification permissions at runtime.
Release APKs and the Android App Bundle can be rebuilt byte-for-byte in the pinned Linux container. Maintainers should follow the Android release guide. See Reproducible builds for the build trust model and public GitHub/Google Play verification procedures.
Testing
# Unit tests
./gradlew test
# Lint
./gradlew lint
# Instrumented tests (requires a device or emulator)
./gradlew connectedAndroidTest
Note that BLE mesh behavior is difficult to emulate; protocol and session logic is covered by unit tests, while radio-level behavior needs real devices.