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664c2dac46
Three changes that all come from the back stack currently being one entry deep, which hides distinctions this PR is what makes matter. Seeding moved out of onCreate. It was there because NavDisplay rejects an empty back stack and effects do not run until after the first composition. Gating the host on the stack instead lets the effect that re-roots on every later crossing do the first one too, so there is one mechanism rather than two. It also stops the start route having to be readable synchronously: onCreate could only seed at all because onboardingState carries an eager CHECKING, and anything read from disk later would have had nothing to offer it. The gate has to test the stack rather than the route, since the route is non-null from the first composition and would compose the host with nothing to show. The crossing guard compares the first entry rather than the last. They are the same value at depth one, but the effect re-runs on every configuration change while the retained scope keeps the stack, so once a destination is pushed onto chat, the top would stop matching the root and every rotation would silently reset the stack. The Bluetooth receiver moves to onCreate and onDestroy. Composition and the Activity cover the same span here, so this is not a lifetime change; it is that a composition-scoped registration can be narrowed by moving the code, which is exactly how it came to be scoped to a destination and stopped firing on the chat route. setRootIfEmpty goes with the onCreate call it existed for. Verified on a Pixel 9a: launch without the empty-backstack crash, rotation both ways with the stack intact, and Bluetooth off then on still logged on the chat route. 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.