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wz-phone/docs/android
Claude 6597b5bd86
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Build Release Binaries / build-amd64 (push) Failing after 3s
docs: incident report + fix spec for capture thread use-after-free crash
SIGSEGV on hangup: capture thread calls writeAudio() via JNI after
teardown() has freed the native engine handle. TOCTOU race between
the nativeHandle==0L check and destroy() on the ViewModel thread.

Fix: CountDownLatch(2) — audio threads count down after exiting loops,
teardown() awaits before destroy(). 2 Kotlin files, no Rust changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-06 09:21:35 +00:00
..

WarzonePhone Android Client

The WZP Android client is a native VoIP application built with Kotlin/Jetpack Compose on top of a Rust audio engine. It connects to WZP relay servers over QUIC, providing encrypted voice calls with adaptive quality, forward error correction, and acoustic echo cancellation.

Quick Start

  1. Build: cd android && ./gradlew assembleRelease (requires NDK 26.1, cargo-ndk)
  2. Install: adb install app/build/outputs/apk/release/app-release.apk
  3. Run: Open "WZ Phone", tap CALL to connect to the hardcoded relay
  4. Relay: Must be running at the configured address (default 172.16.81.125:4433)

Current State (April 2025)

Feature Status
QUIC transport to relay Working
Crypto handshake (X25519 + Ed25519) Working
Opus 24k encoding/decoding Working
Oboe audio I/O (48kHz mono) Working
AEC / AGC signal processing Working
RaptorQ FEC Wired (repair symbols not sent yet)
Jitter buffer Working
Adaptive quality switching Codec-ready, not network-driven yet
Authentication (featherChat) Skipped (relay has no --auth-url)
Media encryption (ChaCha20-Poly1305) Session derived but not applied to packets
Foreground service / wake locks Implemented, not started from UI

Documentation Index

  • Architecture - System design, data flow diagrams, thread model
  • Build Guide - Build environment setup, dependencies, signing
  • Debugging - Crash diagnosis, logcat filters, common issues
  • Maintenance - Code map, dependency management, upgrade paths
  • Roadmap - Planned work and known gaps

Key Design Decisions

  • Rust native engine: All audio processing, codecs, FEC, crypto, and networking run in Rust. Kotlin is UI-only.
  • Lock-free audio: SPSC ring buffers with atomic ordering between Oboe C++ callbacks and the Rust codec thread. No mutexes in the audio path.
  • cargo-ndk: The native library (libwzp_android.so) is cross-compiled for arm64-v8a using cargo-ndk, invoked automatically by Gradle's cargoNdkBuild task.
  • Single-activity Compose: One CallActivity hosts all UI via Jetpack Compose with CallViewModel as the state holder.