x64dbg is an open-source binary debugger for Windows targeting malware analysis and reverse engineering. The architecture is a three-layer system: a GUI layer (Qt-based Windows application), a bridge layer (C API for communication), and a debugger core layer (TitanEngine/GleeBug/StaticEngine backends). The debugger supports x86 and x64 processes with comprehensive features including conditional breakpoints, memory analysis, symbol handling, and an extensive plugin SDK. The codebase demonstrates strong engineering in several areas. The analysis engine implements multiple analysis passes (linear, recursive, control flow, xrefs) with a clean pass-based architecture. The command system uses a flexible registration pattern with consistent error handling. The bridge layer provides a well-defined C API surface for plugins with careful attention to thread safety and marshaling between GUI and debugger threads. Recent development shows active work on Linux support (ElfBug debugger), cross-platform tools (hex viewer, minidump analyzer, remote table), and a comprehensive test framework with headless testing infrastructure. The test system uses convention-based test discovery with script-driven scenarios and plugin-based assertions. Technical debt includes some outdated documentation (docs reference Python 2.7 for CHM generation), mixed use of Qt versions (5.12+ required but some paths reference older configurations), and the inherent complexity of maintaining both Windows debugger and cross-platform analysis tools in one repository. The dependency on precompiled libraries (TitanEngine, Zydis, XEDParse) creates build complexity but is managed through CMake.