Build #20 failed to compile on Android because I over-gated the wzp_proto imports to non-Android. resolve_quality() is compiled on every platform (it's outside the CallEngine impl) and references QualityProfile + CodecId — both platform-independent types from wzp_proto. Move those back to an unconditional import. tracing stays gated (only the desktop start() body logs; the Android stub is silent). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>