Arthas is a production-grade Java diagnostic and monitoring agent developed by Alibaba. It attaches to running JVMs without code changes or restarts, enabling real-time inspection of threads, memory, classes, method invocations, and system properties through an interactive shell (telnet/HTTP/WebSocket) or programmatic APIs. The architecture consists of a core agent (bytecode instrumentation via ASM/ByteKit), a command framework with over 40 built-in commands (watch, trace, stack, dashboard, profiler, etc.), multiple transport protocols (telnet, HTTP, gRPC, MCP for AI integration), and a tunnel server for remote connectivity. It also includes experimental modules for JFR analysis, cluster management, and gRPC-web proxies. Key external dependencies include Netty, OGNL, CFR decompiler, and async-profiler.