Linphone Desktop is a production-grade, cross-platform SIP softphone built on the Linphone C++ SDK and wrapped in a Qt6/QML user interface. It delivers audio/video calls, instant messaging (including group chat, file transfer, reactions, and ephemeral messages), conference scheduling, call recording, and presence management across Windows, macOS, and Linux. The architecture follows a strict MVVM split: model classes run on the Linphone SDK thread and expose Qt signals, while GUI-facing 'Core' classes live on the main thread and communicate with models via a custom SafeConnection template that enforces thread affinity. QML views bind directly to these cores, with list proxies (e.g., ListProxy, SortFilterProxy) providing paginated, filterable models for contact lists, call history, and chat logs. The codebase also integrates advanced features like OIDC/OAuth authentication, LDAP/CardDAV address book sync, end-to-end encryption (LIME/DTLS/SRTP), and system-level integrations (toast notifications, tray icons, screen-sharing, autostart) with per-platform backends. The repository is actively maintained with a modern build system (CMake), comprehensive GitLab CI pipelines (Linux, macOS, Windows, Squish GUI tests), and a substantial localization effort (multiple .ts files).